Selective nerve fiber stimulation for treating heart conditions

• US 20030045909A1
• Filed: 07/24/2002
• Published: 03/06/2003
• Est. Priority Date: 08/31/2001
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: BioControl Medical (B.C.M) Ltd.
• Inventors: Cohen, Ehud, Gross, Yossi, Ayal, Shai
• Granted Patent: US 7,778,703 B2
• Time in Patent Office: Days
• US Class Current: 607/9
• CPC Class Codes: A61N 1/0551 Spinal or peripheral nerve electrodes
• CPC Class Codes: A61N 1/0556 Cuff electrodes
• CPC Class Codes: A61N 1/36007 of urogenital or gastrointestinal organs, e.g. for incontinence control
• CPC Class Codes: A61N 1/36071 Pain
• CPC Class Codes: A61N 1/36114 Cardiac control, e.g. by vagal stimulation stimulating the heart A61N1/362

Abstract

Apparatus for treating a heart condition of a subject is provided, including an electrode device, which is adapted to be coupled to a vagus nerve of the subject. A control unit is adapted to drive the electrode device to apply to the vagus nerve a stimulating current, which is capable of inducing action potentials in a therapeutic direction in a first set and a second set of nerve fibers of the vagus nerve. The control unit is also adapted to drive the electrode device to apply to the vagus nerve an inhibiting current, which is capable of inhibiting the induced action potentials traveling in the therapeutic direction in the second set of nerve fibers, the nerve fibers in the second set having generally larger diameters than the nerve fibers in the first set.

Claims

1. Apparatus for treating a heart condition of a subject, comprising:

an electrode device, adapted to be coupled to a vagus nerve of the subject; and

a control unit, adapted to;

drive the electrode device to apply to the vagus nerve a stimulating current, which is capable of inducing action potentials in a therapeutic direction in a first set and a second set of nerve fibers of the vagus nerve, and

drive the electrode device to apply to the vagus nerve an inhibiting current, which is capable of inhibiting the induced action potentials traveling in the therapeutic direction in the second set of nerve fibers, the nerve fibers in the second set having generally larger diameters than the nerve fibers in the first set.

2. Apparatus according to claim 1,

wherein the therapeutic direction is an efferent therapeutic direction towards a heart of the subject, and

wherein the control unit is adapted to:

drive the electrode device to apply to the vagus nerve the stimulating current, configured to induce action potentials in the efferent therapeutic direction in the first and the second set of nerve fibers, and

drive the electrode device to apply to the vagus nerve the inhibiting current, configured to inhibit the induced action potentials traveling in the efferent therapeutic direction in the second set of nerve fibers.

3. Apparatus according to claim 1,

wherein the therapeutic direction is an afferent therapeutic direction towards a brain of the subject, and

wherein the control unit is adapted to:

drive the electrode device to apply to the vagus nerve the stimulating current, configured to induce action potentials in the afferent therapeutic direction in the first and the second set of nerve fibers, and

drive the electrode device to apply to the vagus nerve the inhibiting current, configured to inhibit the induced action potentials traveling in the afferent therapeutic direction in the second set of nerve fibers.

4. Apparatus according to claim 1, wherein the control unit is adapted to increase a number of action potentials traveling in the therapeutic direction by decreasing an amplitude of the applied inhibiting current.

5. Apparatus according to claim 1, wherein the control unit is adapted to decrease a number of action potentials traveling in the therapeutic direction by increasing an amplitude of the applied inhibiting current.

6. Apparatus according to claim 1, wherein the heart condition includes heart failure, and the apparatus is adapted to treat the heart condition.

7. Apparatus according to claim 1, wherein the heart condition includes cardiac arrhythmia, and the apparatus is adapted to treat the heart condition.

8. Apparatus according to claim 1, comprising an override, adapted to be used by the subject so as to influence the application by the electrode device of the stimulating and inhibiting currents.

9. Apparatus according to claim 1, comprising a pacemaker, wherein the control unit is adapted to drive the pacemaker to apply pacing pulses to a heart of the subject.

10. Apparatus according to claim 1, comprising an implantable cardioverter defibrillator (ICD), wherein the control unit is adapted to drive the ICD to apply energy to a heart of the subject.

11. Apparatus according to claim 1, wherein the control unit is adapted to drive the electrode device to apply the stimulating current in a series of pulses.

12. Apparatus according to claim 1, wherein the control unit is adapted to drive the electrode device to apply the inhibiting current in a series of pulses.

13. Apparatus according to claim 1, wherein the control unit is adapted to receive an electrical signal from the electrode device, and to drive the electrode device to regulate the stimulating current responsive to the electrical signal.

14. Apparatus according to claim 1, wherein the control unit is adapted to receive an electrical signal from the electrode device, and to drive the electrode device to regulate the inhibiting current responsive to the electrical signal.

15. Apparatus according to claim 1, wherein the electrode device comprises a cathode, adapted to apply the stimulating current, and a primary set of anodes, adapted to apply the inhibiting current.

16. Apparatus according to claim 15, wherein the primary set of anodes comprises a primary anode and a secondary anode, adapted to be disposed so that the primary anode is located between the secondary anode and the cathode, and wherein the secondary anode is adapted to apply a current with an amplitude less than about one half an amplitude of a current applied by the primary anode.

17. Apparatus according to claim 1, wherein the control unit is adapted to drive the electrode device to apply the stimulating current so as to regulate a heart rate of the subject.

18. Apparatus according to claim 17, wherein the control unit is adapted to drive the electrode device to regulate an amplitude of the stimulating current so as to regulate the heart rate of the subject.

19. Apparatus according to claim 1, wherein the control unit is adapted to drive the electrode device to apply the inhibiting current so as to regulate a heart rate of the subject.

20. Apparatus according to claim 19, wherein the control unit is adapted to drive the electrode device to regulate an amplitude of the inhibiting current so as to regulate the heart rate of the subject.

21. Apparatus according to claim 1, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents in a series of pulses.

22. Apparatus according to claim 21, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents in a series of about one to 20 pulses.

23. Apparatus according to claim 21, wherein the control unit is adapted to drive the electrode device to configure the pulses to have a duration of between about one and three milliseconds.

24. Apparatus according to claim 21, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents in the series of pulses over a period of between about one and about 200 milliseconds.

25. Apparatus according to claim 21, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents in the series of pulses so as to regulate a heart rate of the subject.

26. Apparatus according to claim 25, wherein the control unit is adapted to regulate the number of pulses in the series of pulses so as to regulate the heart rate of the subject.

27. Apparatus according to claim 25, wherein the control unit is adapted to regulate a duration of each pulse so as to regulate the heart rate of the subject.

28. Apparatus according to claim 25, wherein the control unit is adapted to vary a length of a period of application of the series of pulses so as to regulate the heart rate of the subject.

29. Apparatus according to claim 1, wherein the control unit is adapted to drive the electrode device to apply to the vagus nerve a second inhibiting current, which is capable of inhibiting device-induced action potentials traveling in a non-therapeutic direction opposite the therapeutic direction in the first and second sets of nerve fibers.

30. Apparatus according to claim 29, wherein the control unit is adapted to drive the electrode device to apply the second inhibiting current to the vagus nerve at a primary and a secondary location, the primary location located between the secondary location and an application location of the stimulating current, and to apply at the secondary location a current with an amplitude less than about one half an amplitude of a current applied at the primary location.

31. Apparatus according to claim 1, comprising a sensor unit, wherein the control unit is adapted to receive at least one sensed parameter from the sensor unit, and to drive the electrode device to apply the stimulating and inhibiting currents responsive to the at least one sensed parameter.

32. Apparatus according to claim 31, wherein the control unit is adapted to determine a target heart rate of the subject responsive to the at least one sensed parameter, and wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents so as to adjust a heart rate of the subject towards the target heart rate.

33. Apparatus according to claim 31, wherein the sensor unit comprises a blood pressure sensor, wherein the at least one sensed parameter includes a blood pressure of the subject, and wherein the control unit is adapted to receive the at least one sensed parameter from the blood pressure sensor.

34. Apparatus according to claim 31, wherein the sensor unit comprises a left ventricular pressure (LVP) sensor, wherein the at least one sensed parameter includes an LVP of the subject, and wherein the control unit is adapted to receive the at least one sensed parameter from the LVP sensor.

35. Apparatus according to claim 31, wherein the sensor unit comprises a left ventricular pressure (LVP) sensor, wherein the at least one sensed parameter includes a time derivative of an LVP of the subject, and wherein the control unit is adapted to receive the at least one sensed parameter from the LVP sensor.

36. Apparatus according to claim 31, wherein the at least one sensed parameter includes an indicator of decreased cardiac contractility, and wherein the control unit is adapted to receive the indicator of decreased cardiac contractility.

37. Apparatus according to claim 31, wherein the sensor unit comprises an accelerometer, wherein the at least one sensed parameter includes motion of the subject, and wherein the control unit is adapted to receive the at least one sensed parameter from the accelerometer.

38. Apparatus according to claim 31, wherein the sensor unit comprises a detector of norepinephrine concentration in the subject, wherein the at least one sensed parameter includes a norepinephrine concentration, and wherein the control unit is adapted to receive the at least one sensed parameter from the detector.

39. Apparatus according to claim 31, wherein the sensor unit comprises an impedance cardiography sensor, wherein the at least one sensed parameter includes a parameter generated by the impedance cardiography sensor, and wherein the control unit is adapted to receive the at least one sensed parameter from the detector.

40. Apparatus according to claim 31, wherein the at least one sensed parameter includes an indicator of cardiac output, and wherein the control unit is adapted to receive the indicator of cardiac output.

41. Apparatus according to claim 31, wherein the sensor unit comprises an electrocardiogram (ECG) monitor, wherein the at least one sensed parameter includes an ECG value, and wherein the control unit is adapted to receive the at least one sensed parameter from the ECG monitor.

42. Apparatus according to claim 41, wherein the at least one sensed parameter includes an ECG reading indicative of a presence of arrhythmia, and wherein the control unit is adapted to receive the at least one sensed parameter from the ECG monitor.

43. Apparatus according to claim 31, wherein the at least one sensed parameter includes an indication of a heart rate of the subject, and wherein the control unit is adapted to receive the indication of the heart rate.

44. Apparatus according to claim 43, wherein the at least one sensed parameter includes indications of a plurality of heart rates of the subject at a respective plurality of points in time, and wherein the control unit is adapted to receive the at least one sensed parameter and to determine a measure of variability of heart rate responsive thereto.

45. Apparatus according to claim 31, wherein the sensor unit is adapted to sense an initiation physiological parameter and a termination physiological parameter of the subject, and wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the vagus nerve after a delay, to initiate the delay responsive to the sensing of the initiation physiological parameter, and to set a length of the delay responsive to the termination physiological parameter.

46. Apparatus according to claim 45, wherein the control unit is adapted to determine a target heart rate of the subject responsive to the at least one sensed parameter, and wherein the control unit is adapted to set the delay so as to adjust the heart rate towards the target heart rate.

47. Apparatus according to claim 45, wherein the termination physiological parameter includes an atrioventricular (AV) delay of the subject, and wherein the control unit is adapted to set the length of the delay responsive to the AV delay.

48. Apparatus according to claim 45, wherein the sensor unit comprises an electrocardiogram (ECG) monitor.

49. Apparatus according to claim 48, wherein the initiation physiological parameter includes a P-wave of a cardiac cycle of the subject, and wherein the control unit is adapted to initiate the delay responsive to the sensing of the P-wave.

50. Apparatus according to claim 48, wherein the initiation physiological parameter includes an R-wave of a cardiac cycle of the subject, and wherein the control unit is adapted to initiate the delay responsive to the sensing of the R-wave.

51. Apparatus according to claim 48, wherein the termination physiological parameter includes a difference in time between two features of an ECG signal recorded by the ECG monitor, and wherein the control unit is adapted to set the length of the delay responsive to the difference in time between the two features.

52. Apparatus according to claim 51, wherein the termination physiological parameter includes an R-R interval between a sensing of an R-wave of a first cardiac cycle of the subject and a sensing of an R-wave of a next cardiac cycle of the subject, and wherein the control unit is adapted to set the length of the delay responsive to the R-R interval.

53. Apparatus according to claim 51, wherein the termination physiological parameter includes a P-R interval between a sensing of a P-wave of a cardiac cycle of the subject and a sensing of an R-wave of the cardiac cycle, and wherein the control unit is adapted to set the length of the delay responsive to the P-R interval.

54. Apparatus for treating a heart condition of a subject, comprising:

a cathode, adapted to apply to a vagus nerve of the subject a stimulating current which is capable of inducing action potentials in the vagus nerve; and

a primary and a secondary anode, adapted to be disposed so that the primary anode is located between the secondary anode and the cathode, and adapted to apply to the vagus nerve respective primary and secondary inhibiting currents which are capable of inhibiting action potentials in the vagus nerve.

55. Apparatus according to claim 54, wherein the primary and secondary anodes are adapted to be placed between about 0.5 and about 2.0 millimeters apart from one another.

56. Apparatus according to claim 54, wherein the secondary anode is adapted to apply the secondary inhibiting current with an amplitude equal to between about 2 and about 5 milliamps.

57. Apparatus according to claim 54, wherein the secondary anode is adapted to apply the secondary inhibiting current with an amplitude less than about one half an amplitude of the primary inhibiting current applied by the primary anode.

58. Apparatus according to claim 54, wherein the primary anode comprises a ring electrode adapted to apply a generally uniform current around a circumference of the vagus nerve.

59. Apparatus according to claim 54, wherein the secondary anode comprises a ring electrode adapted to apply a generally uniform current around a circumference of the vagus nerve.

60. Apparatus according to claim 54, wherein the cathode comprises a ring electrode adapted to apply a generally uniform current around a circumference of the vagus nerve.

61. Apparatus according to claim 54, comprising a tertiary anode, adapted to be disposed such that the secondary anode is between the tertiary anode and the primary anode.

62. Apparatus according to claim 54, wherein the heart condition includes heart failure, and the apparatus is adapted to treat the heart condition.

63. Apparatus according to claim 54, wherein the heart condition includes cardiac arrhythmia, and the apparatus is adapted to treat the heart condition.

64. Apparatus according to claim 54, comprising an override, adapted to be used by the subject so as to influence the application by the cathode of the stimulating current and by the anodes of the inhibiting current.

65. Apparatus according to claim 54, comprising a pacemaker, adapted to apply pacing pulses to a heart of the subject.

66. Apparatus according to claim 54, comprising an implantable cardioverter defibrillator (ICD), adapted to apply energy to a heart of the subject.

67. Apparatus according to claim 54, wherein the electrode device comprises an efferent edge, wherein the cathode is adapted to be disposed closer than the anodes to the efferent edge of the electrode device.

68. Apparatus according to claim 54, wherein the cathode is adapted to apply the stimulating current so as to regulate a heart rate of the subject.

69. Apparatus according to claim 54, wherein the anodes are adapted to apply the inhibiting current so as to regulate a heart rate of the subject.

70. Apparatus according to claim 54, wherein the cathode comprises a plurality of discrete cathodes, adapted to be disposed at respective positions around an axis of the vagus nerve, so as to selectively stimulate nerve fibers of the vagus nerve responsive to the positions of the nerve fibers in the vagus nerve.

71. Apparatus according to claim 54, wherein the primary anode comprises a plurality of discrete primary anodes, adapted to be disposed at respective positions around an axis of the vagus nerve.

72. Apparatus according to claim 71, wherein the secondary anode comprises a plurality of discrete secondary anodes, adapted to be disposed at respective positions around the axis of the vagus nerve.

73. Apparatus according to claim 54, comprising a set of one or more blocking anodes, adapted to be disposed such that the cathode is between the set of blocking anodes and the primary anode, and adapted to apply to the vagus nerve a current which is capable of inhibiting action potentials propagating in the vagus nerve in a direction from the cathode towards the set of blocking anodes.

74. Apparatus according to claim 73, wherein the set of blocking anodes comprises a first anode and a second anode, adapted to be disposed such that the first anode is located between the second anode and the cathode, and wherein the second anode is adapted to apply a current with an amplitude less than about one half an amplitude of a current applied by the first anode.

75. Apparatus according to claim 54, wherein the electrode device comprises an afferent edge, wherein the cathode is adapted to be disposed closer than the anodes to the afferent edge of the electrode device.

76. Apparatus according to claim 75, wherein the apparatus is adapted to increase a number of action potentials traveling in an efferent direction by decreasing an amplitude of the primary inhibiting current.

77. Apparatus according to claim 54, comprising a cuff, and an electrically-insulating element coupled to an inner portion of the cuff, wherein the primary anode and the cathode are adapted to be mounted in the cuff and separated from one another by the insulating element.

78. Apparatus according to claim 77, wherein the primary and secondary anodes and the cathode are adapted to be recessed in the cuff so as not to be in direct contact with the vagus nerve.

79. Apparatus according to claim 54, comprising a control unit, adapted to drive the cathode and the anodes to apply the respective currents to the vagus nerve, so as to treat the subject.

80. Apparatus according to claim 79, wherein the control unit is adapted to receive an electrical signal from an electrode, including at least one of:

the cathode, the primary anode, and the secondary anode, and to drive the cathode to regulate the stimulating current responsive to the electrical signal.

81. Apparatus according to claim 79, wherein the control unit is adapted to receive an electrical signal from an electrode, including at least one of:

the cathode, the primary anode, and the secondary anode, and to drive the anodes to regulate the inhibiting currents responsive to the electrical signal.

82. Apparatus according to claim 79, comprising a sensor unit, wherein the control unit is adapted to receive at least one sensed parameter from the sensor unit, and to drive the cathode and the anodes to apply the respective currents to the vagus nerve responsive to the at least one sensed parameter.

83. Apparatus according to claim 82, wherein the control unit is adapted to determine a target heart rate of the subject responsive to the at least one sensed parameter, and wherein the control unit is adapted to drive the cathode and the anodes to apply the respective currents so as to adjust a heart rate of the subject towards the target heart rate.

84. Apparatus according to claim 82, wherein the sensor unit comprises a blood pressure sensor, wherein the at least one sensed parameter includes a blood pressure of the subject, and wherein the control unit is adapted to receive the at least one sensed parameter from the blood pressure sensor.

85. Apparatus according to claim 82, wherein the sensor unit comprises a left ventricular pressure (LVP) sensor, wherein the at least one sensed parameter includes an LVP of the subject, and wherein the control unit is adapted to receive the at least one sensed parameter from the LVP sensor.

86. Apparatus according to claim 82, wherein the sensor unit comprises a left ventricular pressure (LVP) sensor, wherein the at least one sensed parameter includes a time derivative of an LVP of the subject, and wherein the control unit is adapted to receive the at least one sensed parameter from the LVP sensor.

87. Apparatus according to claim 82, wherein the at least one sensed parameter includes an indicator of decreased cardiac contractility, and wherein the control unit is adapted to receive the indicator of decreased cardiac contractility.

88. Apparatus according to claim 82, wherein the sensor unit comprises an accelerometer, wherein the at least one sensed parameter includes motion of the subject, and wherein the control unit is adapted to receive the at least one sensed parameter from the accelerometer.

89. Apparatus according to claim 82, wherein the sensor unit comprises a detector of norepinephrine concentration in the subject, wherein the at least one sensed parameter includes a norepinephrine concentration, and wherein the control unit is adapted to receive the at least one sensed parameter from the detector.

90. Apparatus according to claim 82, wherein the sensor unit comprises an impedance cardiography sensor, wherein the at least one sensed parameter includes a parameter generated by the impedance cardiography sensor, and wherein the control unit is adapted to receive the at least one sensed parameter from the sensor unit.

91. Apparatus according to claim 82, wherein the at least one sensed parameter includes an indicator of cardiac output, and wherein the control unit is adapted to receive the indicator of cardiac output.

92. Apparatus according to claim 82, wherein the at least one sensed parameter includes an indication of a heart rate of the subject, and wherein the control unit is adapted to receive the indication of the heart rate.

93. Apparatus according to claim 92, wherein the at least one sensed parameter includes indications of a plurality of heart rates of the subject at a respective plurality of points in time, and wherein the control unit is adapted to receive the at least one sensed parameter and to determine a measure of variability of heart rate responsive thereto.

94. Apparatus according to claim 82, wherein the sensor unit comprises an electrocardiogram (ECG) monitor, and wherein the control unit is adapted to receive at least one sensed parameter from the ECG monitor.

95. Apparatus according to claim 94, wherein the at least one sensed parameter includes an ECG reading indicative of a presence of arrhythmia, and wherein the control unit is adapted to receive the at least one sensed parameter from the ECG monitor.

96. Apparatus according to claim 54, wherein the cathode is adapted to apply the stimulating current and the anodes are adapted to apply the inhibiting current so as to regulate a heart rate of the subject.

97. Apparatus according to claim 96, wherein the cathode is adapted to vary an amplitude of the applied stimulating current and the anodes are adapted to vary an amplitude of the applied inhibiting current so as to regulate a heart rate of the subject.

98. Apparatus according to claim 96, comprising a sensor unit, adapted to sense an initiation physiological parameter and a termination physiological parameter of the subject, wherein the control unit is adapted to receive the initiation and termination physiological parameters from the sensor unit, to drive the electrode device to apply the stimulating and inhibiting currents to the vagus nerve after a delay, to initiate the delay responsive to the sensing of the initiation physiological parameter, and to set a length of the delay responsive to the termination physiological parameter.

99. Apparatus according to claim 98, wherein the sensor unit is adapted to sense at least one additional sensed parameter, and wherein the control unit is adapted to receive the at least one additional sensed parameter from the sensor unit, to determine a target heart rate of the subject responsive to the at least one additional sensed parameter, and to set the delay so as to adjust the heart rate towards the target heart rate.

100. Apparatus according to claim 98, wherein the termination physiological parameter includes an atrioventricular (AV) delay of the subject, and wherein the control unit is adapted to set the length of the delay responsive to the AV delay.

101. Apparatus according to claim 98, wherein the sensor unit comprises an electrocardiogram (ECG) monitor.

102. Apparatus according to claim 101, wherein the initiation physiological parameter includes a P-wave of a cardiac cycle of the subject, and wherein the control unit is adapted to initiate the delay responsive to the sensing of the P-wave.

103. Apparatus according to claim 101, wherein the initiation physiological parameter includes an R-wave of a cardiac cycle of the subject, and wherein the control unit is adapted to initiate the delay responsive to the sensing of the R-wave.

104. Apparatus according to claim 101, wherein the termination physiological parameter includes a difference between two features of an ECG signal recorded by the ECG monitor, and wherein the control unit is adapted to set the length of the delay responsive to the difference in time between the two features.

105. Apparatus according to claim 104, wherein the termination physiological parameter includes an R-R interval between a sensing of an R-wave of a first cardiac cycle of the subject and a sensing of an R-wave of a next cardiac cycle of the subject, and wherein the control unit is adapted to set the length of the delay responsive to the R-R interval.

106. Apparatus according to claim 104, wherein the termination physiological parameter includes a P-R interval between a sensing of a P-wave of a cardiac cycle of the subject and a sensing of an R-wave of the cardiac cycle, and wherein the control unit is adapted to set the length of the delay responsive to the P-R interval.

107. Apparatus according to claim 54, wherein the cathode and anodes are adapted to apply the stimulating current and the inhibiting current, respectively, in a series of pulses.

108. Apparatus according to claim 107, wherein the cathode and anodes are adapted to apply the stimulating current and the inhibiting current, respectively, in a series of between about one and 20 pulses.

109. Apparatus according to claim 107, wherein the cathode and anodes are adapted to apply the stimulating current and the inhibiting current, respectively, in a series of pulses, each pulse with a duration of between about one and three milliseconds.

110. Apparatus according to claim 107, wherein the cathode and anodes are adapted to apply the stimulating current and the inhibiting current, respectively, in the series of pulses over a period of between about one and about 200 milliseconds.

111. Apparatus according to claim 107, wherein the cathode and anodes are adapted to apply the stimulating current and the inhibiting current, respectively, in the series of pulses so as to regulate a heart rate of the subject.

112. Apparatus according to claim 111, wherein the cathode and the anodes are adapted to regulate the number of pulses in the series of pulses so as to regulate the heart rate of the subject.

113. Apparatus according to claim 111, wherein the cathode and the anodes are adapted to regulate a duration of each pulse so as to regulate the heart rate of the subject.

114. Apparatus according to claim 111, wherein the cathode and the anodes are adapted to vary a length of a period of application of the series of pulses so as to regulate the heart rate of the subject.

115. Apparatus for treating a heart condition of a subject, comprising:

an electrode device, adapted to be coupled to a vagus nerve of the subject;

a sensor unit, adapted to sense an initiation physiological parameter and a termination physiological parameter of the subject; and

a control unit, adapted to;

drive the electrode device to apply to the vagus nerve, after a delay, a current which is capable of inducing action potentials that propagate in the vagus nerve,

initiate the delay responsive to the sensing of the initiation physiological parameter, and

set a length of the delay responsive to the termination physiological parameter.

116. Apparatus according to claim 115, wherein the electrode device is adapted to apply a current that is capable of inducing action potentials that propagate in an efferent direction in the vagus nerve.

117. Apparatus according to claim 115, wherein the electrode device is adapted to apply a current that is capable of inducing action potentials that propagate in an afferent direction in the vagus nerve.

118. Apparatus according to claim 115, wherein the heart condition includes heart failure, and the apparatus is adapted to treat the heart condition.

119. Apparatus according to claim 115, wherein the heart condition includes cardiac arrhythmia, and the apparatus is adapted to treat the heart condition.

120. Apparatus according to claim 115, wherein the sensor unit comprises a single sensor, adapted to sense the initiation physiological parameter and the termination physiological parameter.

121. Apparatus according to claim 115, wherein the termination physiological parameter includes an atrioventricular (AV) delay of the subject, and wherein the control unit is adapted to set the length of the delay responsive to the AV delay.

122. Apparatus according to claim 115, wherein the termination physiological parameter includes a respiration parameter of the subject, and wherein the control unit is adapted to set the length of the delay responsive to the respiration parameter.

123. Apparatus according to claim 115, wherein the control unit is adapted to:

drive the electrode device to apply to the vagus nerve a stimulating current, which is capable of inducing action potentials in a therapeutic direction in a first set and a second set of nerve fibers of the vagus nerve, and

drive the electrode device to apply to the vagus nerve an inhibiting current, which is capable of inhibiting the induced action potentials traveling in the therapeutic direction in the second set of nerve fibers, the nerve fibers in the second set having generally larger diameters than the nerve fibers in the first set.

124. Apparatus according to claim 115, wherein the electrode device comprises:

a cathode, adapted to apply to the vagus nerve a stimulating current which is capable of inducing action potentials in the vagus nerve; and

a primary and a secondary anode, adapted to be disposed so that the primary anode is located between the secondary anode and the cathode, and adapted to apply to the vagus nerve an inhibiting current which is capable of inhibiting action potentials in the vagus nerve.

125. Apparatus according to claim 115, wherein the control unit is adapted to receive an electrical signal from the electrode device, and to drive the electrode device to regulate the current responsive to the electrical signal.

126. Apparatus according to claim 115, wherein the control unit is adapted to drive the electrode device to apply the current so as to regulate a heart rate of the subject.

127. Apparatus according to claim 126, wherein the control unit is adapted to drive the electrode device to vary an amplitude of the current so as to regulate the heart rate of the subject.

128. Apparatus according to claim 115, wherein the sensor unit comprises a blood pressure sensor.

129. Apparatus according to claim 128, wherein the termination physiological parameter includes a blood pressure of the subject, and wherein the control unit is adapted to set the length of the delay responsive to the blood pressure.

130. Apparatus according to claim 128, wherein the sensor unit is adapted to sense a rate-setting parameter of the subject, wherein the rate-setting parameter includes a blood pressure of the subject, and wherein the control unit is adapted to receive the rate-setting parameter from the sensor unit and to drive the electrode device to apply the current responsive to the rate-setting parameter.

131. Apparatus according to claim 115, wherein the control unit is adapted to drive the electrode device to apply the current in a series of pulses.

132. Apparatus according to claim 131, wherein the control unit is adapted to drive the electrode device to apply the current in a series of about one to 20 pulses.

133. Apparatus according to claim 131, wherein the control unit is adapted to configure the pulses to have a duration of between about one and three milliseconds.

134. Apparatus according to claim 131, wherein the control unit is adapted to drive the electrode device to apply the current in the series of pulses over a period of between about one and about 200 milliseconds.

135. Apparatus according to claim 131, wherein the control unit is adapted to drive the electrode device to apply the current in the series of pulses so as to regulate a heart rate of the subject.

136. Apparatus according to claim 135, wherein the control unit is adapted to regulate a number of pulses in the series of pulses so as to regulate the heart rate of the subject.

137. Apparatus according to claim 135, wherein the control unit is adapted to regulate a duration of each pulse so as to regulate the heart rate of the subject.

138. Apparatus according to claim 135, wherein the control unit is adapted to vary a length of a period of application of the series of pulses so as to regulate the heart rate of the subject.

139. Apparatus according to claim 115, wherein the sensor unit is adapted to sense a rate-setting parameter of the subject, and wherein the control unit is adapted to receive the rate-setting parameter from the sensor unit and to drive the electrode device to apply the current responsive to the rate-setting parameter, so as to regulate a heart rate of the subject.

140. Apparatus according to claim 139, wherein the rate-setting parameter includes the initiation physiological parameter, and wherein the control unit is adapted to drive the electrode device to apply the current responsive to the initiation physiological parameter so as to regulate the heart rate of the subject.

141. Apparatus according to claim 139, wherein the rate-setting parameter includes the termination physiological parameter, and wherein the control unit is adapted to drive the electrode device to apply the current responsive to the termination physiological parameter so as to regulate the heart rate of the subject.

142. Apparatus according to claim 139, wherein the sensor unit comprises a left ventricular pressure (LVP) sensor, wherein the rate-setting parameter includes an LVP of the subject, and wherein the control unit is adapted to receive the LVP from the sensor unit, and to drive the electrode device to apply the current responsive to the LVP so as to regulate the heart rate of the subject.

143. Apparatus according to claim 139, wherein the sensor unit comprises a left ventricular pressure (LVP) sensor, wherein the rate-setting parameter includes a time derivative of an LVP of the subject, and wherein the control unit is adapted to receive the LVP from the sensor unit, and to drive the electrode device to apply the current responsive to the time derivative of the LVP so as to regulate the heart rate of the subject.

144. Apparatus according to claim 139, wherein the sensor unit comprises an accelerometer, wherein the rate-setting parameter includes an indication of motion of the subject, and wherein the control unit is adapted to receive the indication of motion from the sensor unit, and to drive the electrode device to apply the current responsive to the indication of motion so as to regulate the heart rate of the subject.

145. Apparatus according to claim 139, wherein the sensor unit comprises a detector of norepinephrine concentration in the subject, wherein the rate-setting parameter includes an indication of a norepinephrine concentration, and wherein the control unit is adapted to receive the indication of the norepinephrine concentration from the sensor unit, and to drive the electrode device to apply the current responsive to the indication of the norepinephrine concentration so as to regulate the heart rate of the subject.

146. Apparatus according to claim 139, wherein the sensor unit comprises an impedance cardiography sensor, and wherein the rate-setting parameter includes a parameter generated by the impedance cardiography sensor, and wherein the control unit is adapted to receive the parameter generated by the impedance cardiography sensor from the sensor unit, and to drive the electrode device to apply the current responsive to the parameter generated by the impedance cardiography sensor so as to regulate the heart rate of the subject.

147. Apparatus according to claim 139, wherein the rate-setting parameter includes an indicator of decreased cardiac contractility, and wherein the control unit is adapted to receive the indicator of decreased cardiac contractility from the sensor unit, and to drive the electrode device to apply the current responsive to the indicator of decreased cardiac contractility so as to regulate the heart rate of the subject.

148. Apparatus according to claim 139, wherein the rate-setting parameter includes an indicator of cardiac output, and wherein the control unit is adapted to receive the indicator of cardiac output from the sensor unit, and to drive the electrode device to apply the current responsive to the indicator of cardiac output so as to regulate the heart rate of the subject.

149. Apparatus according to claim 139, wherein the rate-setting parameter includes an indication of a heart rate of the subject, and wherein the control unit is adapted to receive the indication of the heart rate from the sensor unit, and to drive the electrode device to apply the current responsive to the indication of the heart rate so as to regulate the heart rate of the subject.

150. Apparatus according to claim 149, wherein the rate-setting parameter includes indications of a plurality of heart rates of the subject at a respective plurality of points in time, and wherein the control unit is adapted to receive the indications of the plurality of heart rates, and to drive the electrode device to apply the current responsive to the indications of the plurality of heart rates so as to regulate the heart rate of the subject.

151. Apparatus according to claim 139, wherein the control unit is adapted to determine a target heart rate of the subject responsive to the rate-setting parameter, and wherein the control unit is adapted to drive the electrode device to apply the current so as to adjust a heart rate of the subject towards the target heart rate.

152. Apparatus according to claim 151, wherein the control unit is adapted to set the length of the delay so as to adjust the heart rate towards the target heart rate.

153. Apparatus according to claim 151, wherein the control unit is adapted to access a lookup table of delays, and to set the length of the delay using the lookup table and responsive to the initiation and termination physiological parameters.

154. Apparatus according to claim 115, wherein the sensor unit comprises an electrocardiogram (ECG) monitor.

155. Apparatus according to claim 154, wherein the initiation physiological parameter includes a P-wave of a cardiac cycle of the subject, and wherein the control unit is adapted to initiate the delay responsive to the sensing of the P-wave.

156. Apparatus according to claim 154, wherein the initiation physiological parameter includes an R-wave of a cardiac cycle of the subject, and wherein the control unit is adapted to initiate the delay responsive to the sensing of the R-wave.

157. Apparatus according to claim 154, wherein the initiation physiological parameter includes a Q-wave of a cardiac cycle of the subject, and wherein the control unit is adapted to initiate the delay responsive to the sensing of the Q-wave.

158. Apparatus according to claim 154, wherein the initiation physiological parameter includes a S-wave of a cardiac cycle of the subject, and wherein the control unit is adapted to initiate the delay responsive to the sensing of the S-wave.

159. Apparatus according to claim 154, wherein the termination physiological parameter includes a difference in time between two features of an ECG signal recorded by the ECG monitor, and wherein the control unit is adapted to set the length of the delay responsive to the difference in time between the two features.

160. Apparatus according to claim 159, wherein the termination physiological parameter includes an R-R interval between a sensing of an R-wave of a first cardiac cycle of the subject and a sensing of an R-wave of a next cardiac cycle of the subject, and wherein the control unit is adapted to set the length of the delay responsive to the R-R interval.

161. Apparatus according to claim 160, wherein the termination physiological parameter includes an average of R-R intervals sensed for a number of cardiac cycles, and wherein the control unit is adapted to set the length of the delay responsive to the average of the R-R intervals.

162. Apparatus according to claim 159, wherein the termination physiological parameter includes a P-R interval between a sensing of a P-wave of a cardiac cycle of the subject and a sensing of an R-wave of the cardiac cycle, and wherein the control unit is adapted to set the length of the delay responsive to the P-R interval.

163. Apparatus according to claim 162, wherein the termination physiological parameter includes an average of P-R intervals sensed for a number of cardiac cycles, and wherein the control unit is adapted to set the length of the delay responsive to the average of the P-R intervals.

164. Apparatus for treating a condition of a subject, comprising:

an electrode device, adapted to be coupled to an autonomic nerve of the subject; and

a control unit, adapted to;

drive the electrode device to apply to the nerve a stimulating current, which is capable of inducing action potentials in a therapeutic direction in a first set and a second set of nerve fibers of the nerve, and

drive the electrode device to apply to the nerve an inhibiting current, which is capable of inhibiting the induced action potentials traveling in the therapeutic direction in the second set of nerve fibers, the nerve fibers in the second set having generally larger diameters than the nerve fibers in the first set.

165. Apparatus according to claim 164, wherein the autonomic nerve includes a lacrimal nerve, and wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the lacrimal nerve.

166. Apparatus according to claim 164, wherein the autonomic nerve includes a salivary nerve, and wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the salivary nerve.

167. Apparatus according to claim 164, wherein the autonomic nerve includes a vagus nerve, and wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the vagus nerve.

168. Apparatus according to claim 164, wherein the autonomic nerve includes a pelvic splanchnic nerve, and wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the pelvic splanchnic nerve.

169. Apparatus according to claim 164, wherein the autonomic nerve includes a sympathetic nerve, and wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the sympathetic nerve.

170. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of a lung of the subject, so as to treat the condition.

171. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of a stomach of the subject, so as to treat the condition.

172. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of a pancreas of the subject, so as to treat the condition.

173. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of a small intestine of the subject, so as to treat the condition.

174. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of a liver of the subject, so as to treat the condition.

175. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of a spleen of the subject, so as to treat the condition.

176. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of a kidney of the subject, so as to treat the condition.

177. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of a bladder of the subject, so as to treat the condition.

178. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of a rectum of the subject, so as to treat the condition.

179. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of a large intestine of the subject, so as to treat the condition.

180. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of a reproductive organ of the subject, so as to treat the condition.

181. Apparatus according to claim 164, wherein the control unit is adapted to drive the electrode device to apply the stimulating and inhibiting currents to the nerve so as to affect behavior of an adrenal gland of the subject, so as to treat the condition.

182. Apparatus for treating a condition of a subject, comprising:

a cathode, adapted to apply to an autonomic nerve of the subject a stimulating current which is capable of inducing action potentials in the nerve; and

a primary and a secondary anode, adapted to be disposed so that the primary anode is located between the secondary anode and the cathode, and adapted to apply to the nerve respective primary and secondary inhibiting currents which are capable of inhibiting action potentials in the nerve.

183. Apparatus according to claim 182, wherein the autonomic nerve includes a lacrimal nerve, and wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the lacrimal nerve.

184. Apparatus according to claim 182, wherein the autonomic nerve includes a salivary nerve, and wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the salivary nerve.

185. Apparatus according to claim 182, wherein the autonomic nerve includes a vagus nerve, and wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the vagus nerve.

186. Apparatus according to claim 182, wherein the autonomic nerve includes a pelvic splanchnic nerve, and wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the pelvic splanchnic nerve.

187. Apparatus according to claim 182, wherein the autonomic nerve includes a sympathetic nerve, and wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the sympathetic nerve.

188. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of a lung of the subject, so as to treat the condition.

189. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of a stomach of the subject, so as to treat the condition.

190. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of a pancreas of the subject, so as to treat the condition.

191. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of a small intestine of the subject, so as to treat the condition.

192. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of a liver of the subject, so as to treat the condition.

193. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of a spleen of the subject, so as to treat the condition.

194. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of a kidney of the subject, so as to treat the condition.

195. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of a bladder of the subject, so as to treat the condition.

196. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of a rectum of the subject, so as to treat the condition.

197. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of a large intestine of the subject, so as to treat the condition.

198. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of a reproductive organ of the subject, so as to treat the condition.

199. Apparatus according to claim 182, wherein the cathode and anodes are adapted to apply the stimulating and inhibiting currents, respectively, to the nerve so as to affect behavior of an adrenal gland of the subject, so as to treat the condition.

200. A method for treating a heart condition of a subject, comprising:

applying, to a vagus nerve of the subject, a stimulating current which is capable of inducing action potentials in a therapeutic direction in a first set and a second set of nerve fibers of the vagus nerve; and

applying to the vagus nerve an inhibiting current which is capable of inhibiting the induced action potentials traveling in the therapeutic direction in the second set of nerve fibers, the nerve fibers in the second set having generally larger diameters than the nerve fibers in the first set.

201. A method according to claim 200,

wherein the therapeutic direction is an efferent therapeutic direction towards a heart of the subject,

wherein applying the stimulating current comprises applying the stimulating current so as to induce the action potentials in the efferent therapeutic direction in the first and the second set of nerve fibers, and

wherein applying the inhibiting current comprises applying the inhibiting current so as to inhibit the induced action potentials traveling in the efferent therapeutic direction in the second set of nerve fibers.

202. A method according to claim 200,

wherein the therapeutic direction is an afferent therapeutic direction towards a brain of the subject,

wherein applying the stimulating current comprises applying the stimulating current so as to induce the action potentials in the afferent therapeutic direction in the first and the second set of nerve fibers, and

wherein applying the inhibiting current comprises applying the inhibiting current so as to inhibit the induced action potentials traveling in the afferent therapeutic direction in the second set of nerve fibers.

203. A method according to claim 200, comprising increasing a number of action potentials traveling in the therapeutic direction by decreasing an amplitude of the applied inhibiting current.

204. A method according to claim 200, wherein the heart condition includes heart failure, and wherein applying the stimulating and inhibiting currents comprises applying the stimulating and inhibiting currents so as to treat the heart condition.

205. A method according to claim 200, wherein the heart condition includes cardiac arrhythmia, and wherein applying the stimulating and inhibiting currents comprises applying the stimulating and inhibiting currents so as to treat the heart condition.

206. A method according to claim 200, comprising receiving an override instruction from the subject, and regulating the application of the stimulating and inhibiting currents responsive to the override instruction.

207. A method according to claim 200, comprising sensing a physiological state of the subject and driving a pacemaker to apply pacing pulses to a heart of the subject responsive to the physiological state, wherein applying the stimulating current comprises applying the stimulating current responsive to the physiological state.

208. A method according to claim 200, comprising sensing a physiological state of the subject and driving an implantable cardioverter defibrillator to apply energy to a heart of the subject responsive to the physiological state, wherein applying the stimulating current comprises applying the stimulating current responsive to the physiological state.

209. A method according to claim 200, wherein applying the stimulating current comprises applying the stimulating current in a series of pulses.

210. A method according to claim 200, wherein applying the inhibiting current comprises applying the inhibiting current in a series of pulses.

211. A method according to claim 200, wherein applying the stimulating current comprises applying the stimulating current so as to regulate a heart rate of the subject.

212. A method according to claim 211, wherein applying the stimulating current so as to regulate the heart rate of the subject comprises regulating an amplitude of the stimulating current so as to regulate the heart rate of the subject.

213. A method according to claim 200, wherein applying the inhibiting current comprises applying the inhibiting current so as to regulate a heart rate of the subject.

214. A method according to claim 213, wherein applying the inhibiting current so as to regulate the heart rate of the subject comprises regulating an amplitude of the inhibiting current so as to regulate the heart rate of the subject.

215. A method according to claim 200, comprising applying to the vagus nerve a supplementary inhibiting current, which is capable of inhibiting induced action potentials traveling in a non-therapeutic direction opposite the therapeutic direction in the first and second sets of nerve fibers.

216. A method according to claim 215, wherein applying the supplementary inhibiting current comprises applying a primary supplementary inhibiting current and a secondary supplementary inhibiting current.

217. A method according to claim 200, wherein applying the stimulating current comprises applying the stimulating current at a stimulating location, and wherein applying the inhibiting current comprises applying the inhibiting current at a primary and a secondary inhibiting location, the primary inhibiting location located between the secondary inhibiting location and the stimulating location.

218. A method according to claim 217, wherein applying the inhibiting current at the secondary inhibiting location comprises applying a current with an amplitude less than about one half an amplitude of a current applied at the primary inhibiting location.

219. A method according to claim 217, comprising:

applying a primary supplementary inhibiting current at a primary supplementary inhibiting location; and

applying a secondary supplementary inhibiting current at a secondary supplementary inhibiting location, the primary supplementary inhibiting location located between the secondary supplementary inhibiting location and the stimulating location, and wherein the primary and secondary supplementary inhibiting currents are capable of inhibiting induced action potentials traveling in a non-therapeutic direction opposite the therapeutic direction in the first and second sets of nerve fibers.

220. A method according to claim 219, wherein applying the secondary supplementary inhibiting current at the secondary supplementary inhibiting location comprises applying a current with an amplitude less than about one half an amplitude of a current applied at the primary supplementary inhibiting location.

221. A method according to claim 200, wherein applying the stimulating and inhibiting currents comprises applying the stimulating and inhibiting currents in respective series of pulses.

222. A method according to claim 221, wherein applying the stimulating and inhibiting currents comprises applying the stimulating and inhibiting currents in respective series of about one to 20 pulses.

223. A method according to claim 221, wherein applying the stimulating and inhibiting currents comprises applying the stimulating and inhibiting currents in respective series of pulses, each pulse with a duration of between about one and three milliseconds.

224. A method according to claim 221, wherein applying the stimulating and inhibiting currents comprises applying the stimulating and inhibiting currents in the respective series of pulses over a period of between about one and about 200 milliseconds.

225. A method according to claim 221, wherein applying the stimulating and inhibiting currents comprises applying the stimulating and inhibiting currents in the respective series of pulses so as to regulate a heart rate of the subject.

226. A method according to claim 225, wherein applying the stimulating and inhibiting currents comprises regulating the number of pulses in the respective series of pulses so as to regulate the heart rate of the subject.

227. A method according to claim 225, wherein applying the stimulating and inhibiting currents comprises regulating a duration of each pulse so as to regulate the heart rate of the subject.

228. A method according to claim 225, wherein applying the stimulating and inhibiting currents comprises varying a length of a period of application of the respective series of pulses so as to regulate the heart rate of the subject.

229. A method according to claim 200, comprising receiving at least one sensed parameter, and applying the stimulating and inhibiting currents responsive to the at least one sensed parameter.

230. A method according to claim 229, comprising determining a target heart rate of the subject responsive to the at least one sensed parameter, wherein applying the stimulating and inhibiting currents comprises applying the stimulating and inhibiting currents so as to adjust a heart rate of the subject towards the target heart rate.

231. A method according to claim 229, wherein the at least one sensed parameter includes an indication of a blood pressure of the subject, and wherein receiving the at least one sensed parameter comprises receiving the indication of the blood pressure.

232. A method according to claim 229, wherein the at least one sensed parameter includes an indication of a left ventricular pressure (LVP) of the subject, and wherein receiving the at least one sensed parameter comprises receiving the indication of the LVP.

233. A method according to claim 229, wherein the at least one sensed parameter includes an indication of a time derivative of a left ventricular pressure (LVP) of the subject, and wherein receiving the at least one sensed parameter comprises receiving the indication of the time derivative of the LVP.

234. A method according to claim 229, wherein the at least one sensed parameter includes an indication of decreased cardiac contractility of the subject, and wherein receiving the at least one sensed parameter comprises receiving the indication of decrease cardiac contractility.

235. A method according to claim 229, wherein the at least one sensed parameter includes an indication of motion of the subject, and wherein receiving the at least one sensed parameter comprises receiving the indication of motion.

236. A method according to claim 229, wherein the at least one sensed parameter includes an indication of a norepinephrine concentration in the subject, and wherein receiving the at least one sensed parameter comprises receiving the indication of the norepinephrine concentration.

237. A method according to claim 229, wherein the at least one sensed parameter includes a parameter determined by impedance cardiography, and wherein receiving the at least one sensed parameter comprises receiving the parameter determined by impedance cardiography.

238. A method according to claim 229, wherein the at least one sensed parameter includes an indication of cardiac output, and wherein receiving the at least one sensed parameter comprises receiving the indication of cardiac output.

239. A method according to claim 229, wherein the at least one sensed parameter includes an electrocardiogram (ECG) value, and wherein receiving the at least one sensed parameter comprises receiving the ECG value.

240. A method according to claim 239, wherein the at least one sensed parameter includes an ECG value indicative of a presence of arrhythmia, and wherein receiving the at least one sensed parameter comprises receiving the ECG value.

241. A method according to claim 229, wherein the at least one sensed parameter includes an indication of a heart rate of the subject, and wherein receiving the at least one sensed parameter comprises receiving the indication of the heart rate.

242. A method according to claim 241, wherein the at least one sensed parameter includes indications of a plurality of heart rates of the subject at a respective plurality of points in time, and wherein receiving the at least one sensed parameter comprises receiving the indications of the plurality of heart rates and determining a measure of variability of heart rate responsive thereto.

243. A method according to claim 229, comprising sensing an initiation physiological parameter and a termination physiological parameter of the subject, wherein applying the stimulating and inhibiting currents comprises:

applying the stimulating and inhibiting currents to the vagus nerve after a delay;

initiating the delay responsive to the sensing of the initiation physiological parameter; and

setting a length of the delay responsive to the termination physiological parameter.

244. A method according to claim 243, comprising determining a target heart rate of the subject responsive to the at least one sensed parameter, wherein setting the length of the delay comprises setting the length of the delay so as to adjust a heart rate of the subject towards the target heart rate.

245. A method according to claim 243, wherein the termination physiological parameter includes an atrioventricular (AV) delay of the subject, and wherein setting the length of the delay comprises setting the length of the delay responsive to the AV delay.

246. A method according to claim 243, wherein the initiation physiological parameter includes a P-wave of a cardiac cycle of the subject, and wherein initiating the delay comprises initiating the delay responsive to the sensing of the P-wave.

247. A method according to claim 243, wherein the initiation physiological parameter includes an R-wave of a cardiac cycle of the subject, and wherein initiating the delay comprises initiating the delay responsive to the sensing of the R-wave.

248. A method according to claim 243, wherein the termination physiological parameter includes a difference in time between two features of an ECG signal recorded by the ECG monitor, and wherein setting the length of the delay comprises setting the length of the delay responsive to the difference in time between the two features.

249. A method according to claim 248, wherein the termination physiological parameter includes an R-R interval between a sensing of an R-wave of a first cardiac cycle of the subject and a sensing of an R-wave of a next cardiac cycle of the subject, and wherein setting the length of the delay comprises setting the length of the delay responsive to the R-R interval.

250. A method according to claim 248, wherein the termination physiological parameter includes a P-R interval between a sensing of a P-wave of a cardiac cycle of the subject and a sensing of an R-wave of the cardiac cycle, and wherein setting the length of the delay comprises setting the length of the delay responsive to the P-R interval.

251. A method for treating a heart condition of a subject, comprising:

applying, to a vagus nerve of the subject, at a stimulation location, a stimulating current which is capable of inducing action potentials in the vagus nerve, so as to treat the subject; and

applying to the vagus nerve at a primary and a secondary location, the primary location located between the secondary location and the stimulation location, an inhibiting current which is capable of inhibiting action potentials in the vagus nerve.

252. A method according to claim 251, wherein the primary and secondary locations are between about 0.5 and about 2.0 millimeters apart from one another, and wherein applying the inhibiting current comprises applying the inhibiting current at the primary and secondary locations.

253. A method according to claim 251, wherein applying the inhibiting current at the secondary location comprises applying the inhibiting current at the secondary location with an amplitude equal to between about 2 and about 5 milliamps.

254. A method according to claim 251, wherein applying the inhibiting current at the secondary location comprises applying the inhibiting current at the secondary location with an amplitude less than about one half an amplitude of the inhibiting current applied at the primary location.

255. A method according to claim 251, wherein applying the inhibiting current at the primary location comprises applying a generally uniform current around a circumference of the vagus nerve at the primary location.

256. A method according to claim 251, wherein applying the inhibiting current at the secondary location comprises applying a generally uniform current around a circumference of the vagus nerve at the secondary location.

257. A method according to claim 251, wherein applying the stimulating current comprises applying a generally uniform current around a circumference of the vagus nerve at the stimulation location.

258. A method according to claim 251, wherein applying the inhibiting current comprises applying to the vagus nerve the inhibiting current at a tertiary location, the tertiary location located such that the secondary location is between the tertiary location and the primary location.

259. A method according to claim 251, wherein the stimulation location is located closer than the primary and secondary locations to a heart of the subject, with respect to action potentials traveling in the vagus nerve,

wherein applying the stimulating current comprises applying the stimulating current at the stimulation location, and

wherein applying the inhibiting current comprises applying the inhibiting current at the primary and secondary locations.

260. A method according to claim 251, wherein applying the stimulating current comprises applying the stimulating current so as to regulate a heart rate of the subject.

261. A method according to claim 251, wherein applying the inhibiting current comprises applying the inhibiting current so as to regulate a heart rate of the subject.

262. A method according to claim 251, wherein the stimulation location comprises a plurality of discrete stimulation locations located at respective locations around an axis of the vagus nerve, and wherein applying the stimulating current at the stimulation location comprises applying the stimulating current at the plurality of discrete stimulation locations, so as to selectively stimulate nerve fibers of the vagus nerve responsive to positions of the nerve fibers in the vagus nerve.

263. A method according to claim 251, comprising applying to the vagus nerve at one or more supplementary locations, the supplementary locations located so that the stimulation location is between the supplementary locations and the primary location, an inhibiting current which is capable of inhibiting action potentials propagating in the vagus nerve in a direction from the stimulation location towards the supplementary locations.

264. A method according to claim 251, wherein applying the stimulating and inhibiting currents comprises applying the stimulating and inhibiting currents so as to regulate a heart rate of the subject.

265. A method according to claim 251, wherein applying the stimulating current comprises applying the stimulating current in a series of pulses.

266. A method according to claim 251, wherein applying the inhibiting current comprises applying the inhibiting current in a series of pulses.

267. A method according to claim 251, wherein the primary location comprises a plurality of discrete primary locations located at respective locations around an axis of the vagus nerve, and wherein applying the inhibiting current at the primary location comprises applying the inhibiting current at the plurality of discrete primary locations.

268. A method according to claim 267, wherein the secondary location comprises a plurality of discrete secondary locations located at respective locations around an axis of the vagus nerve, and wherein applying the inhibiting current at the secondary location comprises applying the inhibiting current at the plurality of discrete secondary locations.

269. A method according to claim 251, wherein the stimulation location is located closer than the primary and secondary locations to a brain of the subject, with respect to action potentials traveling in the vagus nerve,

wherein applying the stimulating current comprises applying the stimulating current at the stimulation location, and

wherein applying the inhibiting current comprises applying the inhibiting current at the primary and secondary locations.

270. A method according to claim 269, comprising increasing a number of action potentials traveling towards a heart of the subject by decreasing an amplitude of the applied inhibiting current.

271. A method according to claim 251, comprising receiving at least one sensed parameter, wherein applying the stimulating and inhibiting currents comprises applying the stimulating and inhibiting currents responsive to the at least one sensed parameter.

272. A method according to claim 271, comprising determining a target heart rate of the subject responsive to the at least one sensed parameter, and wherein applying the stimulating and inhibiting currents comprises applying the stimulating and inhibiting currents so as to adjust a heart rate of the subject towards the target heart rate.

273. A method according to claim 271, wherein the at least one sensed parameter includes an indication of a heart rate of the subject, and wherein receiving the at least one sensed parameter comprises receiving the indication of the heart rate.

274. A method according to claim 271, wherein the at least one sensed parameter includes an electrocardiogram (ECG) value, and wherein receiving the at least one sensed parameter comprises receiving the ECG value.

275. A method according to claim 271, comprising sensing an initiation physiological parameter and a termination physiological parameter of the subject, wherein applying the stimulating and inhibiting currents comprises:

applying the stimulating and inhibiting currents to the vagus nerve after a delay;

initiating the delay responsive to the sensing of the initiation physiological parameter; and

setting a length of the delay responsive to the termination physiological parameter.

276. A method according to claim 275, comprising determining a target heart rate of the subject responsive to the at least one sensed parameter, and wherein setting the length of the delay comprises setting the length of the delay so as to adjust a heart rate of the subject towards the target heart rate.

277. A method for treating a heart condition of a subject, comprising:

sensing an initiation physiological parameter and a termination physiological parameter of the subject;

setting a length of a delay period responsive to the termination physiological parameter;

initiating the delay period responsive to the initiation parameter; and

upon completion of the delay period, applying, to a vagus nerve of the subject, a current which is capable of inducing action potentials that propagate in the vagus nerve.

278. A method according to claim 277, wherein applying the current comprises applying the current so as to induce action potentials that propagate in an efferent direction in the vagus nerve.

279. A method according to claim 277, wherein applying the current comprises applying the current so as to induce action potentials that propagate in an afferent direction in the vagus nerve.

280. A method according to claim 277, wherein the heart condition includes heart failure, and wherein applying the current comprises applying the current so as to treat the heart condition.

281. A method according to claim 277, wherein the heart condition includes cardiac arrhythmia, and wherein applying the current comprises applying the current so as to treat the heart condition.

282. A method according to claim 277, wherein the termination physiological parameter includes an atrioventricular (AV) delay of the subject, and wherein setting the length of the delay period comprises setting the length of the delay period responsive to the AV delay.

283. A method according to claim 277, wherein the termination physiological parameter includes a respiration parameter of the subject, and wherein setting the length of the delay period comprises setting the length of the delay period responsive to the respiration parameter.

284. A method according to claim 277, wherein applying the current comprises:

applying to the vagus nerve a stimulating current, which is capable of inducing action potentials in a therapeutic direction in a first set and a second set of nerve fibers of the vagus nerve; and

applying to the vagus nerve an inhibiting current, which is capable of inhibiting the induced action potentials traveling in the therapeutic direction in the second set of nerve fibers, the nerve fibers in the second set having generally larger diameters than the nerve fibers in the first set.

285. A method according to claim 277, wherein applying the current comprises:

applying to the vagus nerve, at a stimulation location, a stimulating current which is capable of inducing action potentials in the vagus nerve; and

applying to the vagus nerve at a primary and a secondary location, the primary location located between the secondary location and the stimulation location, an inhibiting current which is capable of inhibiting action potentials in the vagus nerve.

286. A method according to claim 277, wherein the termination physiological parameter includes an indication of a blood pressure of the subject, and wherein setting the length of the delay period comprises setting the length of the delay period responsive to the indication of the blood pressure.

287. A method according to claim 277, wherein sensing the initiation physiological parameter includes sensing a P-wave of a cardiac cycle of the subject, and wherein initiating the delay period comprises initiating the delay period responsive to the sensing of the P-wave.

288. A method according to claim 277, wherein sensing the initiation physiological parameter includes sensing an R-wave of a cardiac cycle of the subject, and wherein initiating the delay period comprises initiating the delay period responsive to the sensing of the R-wave.

289. A method according to claim 277, wherein sensing the initiation physiological parameter includes sensing a Q-wave of a cardiac cycle of the subject, and wherein initiating the delay period comprises initiating the delay period responsive to the sensing of the Q-wave.

290. A method according to claim 277, wherein sensing the initiation physiological parameter includes sensing an S-wave of a cardiac cycle of the subject, and wherein initiating the delay period comprises initiating the delay period responsive to the sensing of the S-wave.

291. A method according to claim 277, wherein applying the current comprises applying the current so as to regulate a heart rate of the subject.

292. A method according to claim 291, wherein applying the current comprises regulating an amplitude of the current so as to regulate the heart rate of the subject.

293. A method according to claim 277, wherein applying the current comprises applying the current in a series of pulses.

294. A method according to claim 293, wherein applying the current comprises applying the current in a series of about one to 20 pulses.

295. A method according to claim 293, wherein applying the current comprises applying the current in a series of pulses, each pulse with a duration of between about one and three milliseconds.

296. A method according to claim 293, wherein applying the current comprises applying the current in the series of pulses over a period of between about one and about 200 milliseconds.

297. A method according to claim 293, wherein applying the current comprises applying the current in the series of pulses so as to regulate a heart rate of the subject.

298. A method according to claim 297, wherein applying the current comprises regulating a number of pulses in the series of pulses so as to regulate the heart rate of the subject.

299. A method according to claim 297, wherein applying the current comprises regulating a duration of each pulse so as to regulate the heart rate of the subject.

300. A method according to claim 297, wherein applying the current comprises varying a length of a period of application of the series of pulses so as to regulate the heart rate of the subject.

301. A method according to claim 277, comprising sensing a rate-setting parameter of the subject, wherein applying the current comprises applying the current responsive to the rate-setting parameter, so as to regulate a heart rate of the subject.

302. A method according to claim 301, wherein the rate-setting parameter includes the initiation physiological parameter, and wherein applying the current comprises applying the current responsive to the initiation physiological parameter so as to regulate the heart rate of the subject.

303. A method according to claim 301, wherein the rate-setting parameter includes the termination physiological parameter, and wherein applying the current comprises applying the current responsive to the termination physiological parameter so as to regulate the heart rate of the subject.

304. A method according to claim 301, wherein the rate-setting parameter includes an indication of a blood pressure of the subject, and wherein applying the current comprises applying the current responsive to the indication of the blood pressure, so as to regulate the heart rate of the subject.

305. A method according to claim 301, wherein the rate-setting parameter includes an indication of a left ventricular pressure (LVP) of the subject, and wherein applying the current comprises applying the current responsive to the indication of the LVP, so as to regulate the heart rate of the subject.

306. A method according to claim 301, wherein the rate-setting parameter includes an indication of a time derivative of a left ventricular pressure (LVP) of the subject, and wherein applying the current comprises applying the current responsive to the indication of the time derivative of the LVP, so as to regulate the heart rate of the subject.

307. A method according to claim 301, wherein the rate-setting parameter includes an indication of motion of the subject, and wherein applying the current comprises applying the current responsive to the indication of motion, so as to regulate the heart rate of the subject.

308. A method according to claim 301, wherein the rate-setting parameter includes an indication of a norepinephrine concentration in the subject, and wherein applying the current comprises applying the current responsive to the indication of the norepinephrine concentration, so as to regulate the heart rate of the subject.

309. A method according to claim 301, wherein the rate-setting parameter includes a parameter determined by impedance cardiography, and wherein applying the current comprises applying the current responsive to the parameter determined by impedance cardiography, so as to regulate the heart rate of the subject.

310. A method according to claim 301, wherein the rate-setting parameter includes an indicator of decreased cardiac contractility, and wherein applying the current comprises applying the current responsive to the indicator of decreased cardiac contractility, so as to regulate the heart rate of the subject.

311. A method according to claim 301, wherein the rate-setting parameter includes an indication of cardiac output, and wherein applying the current comprises applying the current responsive to the indication of cardiac output, so as to regulate the heart rate of the subject.

312. A method according to claim 301, wherein the rate-setting parameter includes an indication of a heart rate of the subject, and wherein applying the current comprises applying the current responsive to the indication of the heart rate, so as to regulate the heart rate of the subject.

313. A method according to claim 301, comprising determining a target heart rate of the subject responsive to the rate-setting parameter, and wherein applying the current comprises applying the current so as to adjust a heart rate of the subject towards the target heart rate.

314. A method according to claim 313, wherein setting the delay period comprises setting the delay period so as to adjust the heart rate towards the target heart rate.

315. A method according to claim 313, wherein setting the delay period comprises accessing one or more values stored a lookup table of delay periods, and setting the delay period responsive to the values and to the initiation and termination physiological parameters.

316. A method according to claim 277, comprising sensing an electrocardiogram (ECG) signal, wherein the termination physiological parameter includes a difference in time between two features of the ECG signal, and wherein setting the length of the delay period comprises setting the length of the delay period responsive to the difference in time between the two features.

317. A method according to claim 316, wherein the termination physiological parameter includes an R-R interval between a sensing of an R-wave of a first cardiac cycle of the subject and a sensing of an R-wave of a next cardiac cycle of the subject, and wherein setting the length of the delay period comprises setting the length of the delay period responsive to the R-R interval.

318. A method according to claim 317, wherein the termination physiological parameter includes an average of R-R intervals sensed for a number of cardiac cycles, and wherein setting the length of the delay period comprises setting the length of the delay period responsive to the average of the R-R intervals.

319. A method according to claim 316, wherein the termination physiological parameter includes a P-R interval between a sensing of a P-wave of a cardiac cycle of the subject and a sensing of an R-wave of the cardiac cycle, and wherein setting the length of the delay period comprises setting the length of the delay period responsive to the P-R interval.

320. A method according to claim 319, wherein the termination physiological parameter includes an average of P-R intervals sensed for a number of cardiac cycles, and wherein setting the length of the delay period comprises setting the length of the delay period responsive to the average of the P-R intervals.

321. A method for treating a condition of a subject, comprising:

applying, to an autonomic nerve of the subject, a stimulating current which is capable of inducing action potentials in a therapeutic direction in a first set and a second set of nerve fibers of the nerve; and

applying to the nerve an inhibiting current which is capable of inhibiting the induced action potentials traveling in the therapeutic direction in the second set of nerve fibers, the nerve fibers in the second set having generally larger diameters than the nerve fibers in the first set.

322. A method for treating a condition of a subject, comprising:

applying, to an autonomic nerve of the subject, at a stimulation location, a stimulating current which is capable of inducing action potentials in the nerve, so as to treat the subject; and

applying to the nerve at a primary and a secondary location, the primary location located between the secondary location and the stimulation location, an inhibiting current which is capable of inhibiting action potentials in the nerve.