Apparatus and process for reducing the susceptability of active implantable medical devices to medical procedures such as magnetic resonance imaging

• US 20050197677A1
• Filed: 03/31/2005
• Published: 09/08/2005
• Est. Priority Date: 02/12/2004
• Status: Active Grant

• Current Assignee: Greatbatch-Sierra, Inc.
• Original Assignee: Greatbatch-Sierra, Inc.
• Inventors: Stevenson, Robert A.
• Granted Patent: US 7,765,005 B2
• Time in Patent Office: Days
• US Class Current: 607/36
• CPC Class Codes: A61N 1/086 Magnetic resonance imaging [MRI] compatible leads
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents
• CPC Class Codes: A61N 1/3754 Feedthroughs
• CPC Class Codes: H01F 17/06 with core substantially closed in itself, e.g. toroid
• CPC Class Codes: H01F 2017/065 Core mounted around conductor to absorb noise, e.g. EMI filter
• CPC Class Codes: H01F 2017/067 Core with two or more holes to lead through conductor
• CPC Class Codes: H01G 4/35 Feed-through capacitors or anti-noise capacitors
• CPC Class Codes: H03H 2001/0042 Wound, ring or feed-through type capacitor
• CPC Class Codes: H03H 2001/0057 comprising magnetic material

Abstract

A feedthrough terminal assembly for an active implantable medical device (AIMD) includes a plurality of leadwires extending from electronic circuitry of the AIMD, and a lossy ferrite inductor through which the leadwires extend in non-conductive relation for increasing the impedance of the leadwires at selected RF frequencies and reducing magnetic flux core saturation of the lossy ferrite inductor through phase cancellation of signals carried by the leadwires. A process is also provided for filtering electromagnetic interference (EMI) in an implanted leadwire extending from an AIMD into body fluids or tissue, wherein the leadwire is subjected to occasional high-power electromagnetic fields such as those produced by medical diagnostic equipment including magnetic resonance imaging.

Claims

1. A feedthrough terminal assembly for an active implantable medical device (AIMD), comprising:

a plurality of leadwires extending from electronic circuitry of the AIMD; and

a lossy ferrite inductor through which the leadwires extend in non-conductive relation for increasing the impedence of the leadwires at selected RF frequencies and reducing magnetic flux core saturation of the lossy ferrite inductor through phase cancellation of signals carried by the leadwires.

2. The assembly of claim 1, wherein the active implantable medical device comprises a cardiac pacemaker, an implantable defibrillator, a congestive heart failure device, a hearing implant, a neurostimulator, a drug pump, a ventricular assist device, an insulin pump, a spinal cord stimulator, an implantable sensing system, an artificial heart, an incontinence device, a bone growth stimulator, a gastric pacemaker or a prosthetic device.

3. The assembly of claim 1, wherein the leadwires comprise a first leadwire extending from the electronic circuitry of the AIMD through a housing of the AIMD to a point within a human body, and a second leadwire conductively coupled to at least a portion of the AIMD housing and the AIMD circuitry.

4. The assembly of claim 1, including a conformal coating over the lossy ferrite inductor, wherein the conformal coating comprises Paralene C, D, E, or N.

5. The assembly of claim 1, including an insulator disposed between the lossy ferrite inductor and the leadwires.

6. The assembly of claim 1, including one or more additional lossy ferrite inductors through which the leadwires extend in non-conductive relation.

7. The assembly of claim 6, wherein the lossy ferrite inductors are disposed adjacent to one another.

8. The assembly of claim 7, wherein the lossy ferrite inductors are each comprised of materials having different physical or electrical properties.

9. The assembly of claim 6, including a hermetic insulator disposed between the leadwires and a ferrule, wherein the lossy ferrite inductors are disposed on opposite sides of the insulator.

10. The assembly of claim 1, including a hermetic insulator disposed between the leadwires and a ferrule, wherein the lossy ferrite inductor is bonded to the insulator to form a beam-like structure.

11. The assembly of claim 1, wherein the lossy ferrite inductor includes an aperture through which a leak detection gas can be detected.

12. The assembly of claim 1, wherein at least one of the leadwires is wound about the lossy ferrite inductor to form multiple turns, and wherein adjacent portions of the wound leadwire are electrically insulated from one another.

13. The assembly of claim 12, wherein the lossy ferrite inductor includes a notch for receiving the wound leadwire.

14. The assembly of claim 12, wherein the lossy ferrite inductor includes multiple notches therein.

15. The assembly of claim 12, wherein at least two leadwires are wound about the lossy ferrite inductor to form one or more turns, and wherein the turn count for the at least two leadwires is not equal.

16. The assembly of claim 1, including means for maintaining the lossy ferrite inductor in close association with the AIMD without laminating or bonding the inductor to another component.

17. The assembly of claim 16, wherein the maintaining means comprises a mechanical lock, a deformation in the leadwire, a cured polymer, or a wire bond pad attached to the leadwire.

18. The assembly of claim 1, wherein at least two of the leadwires are routed through the lossy ferrite inductor in opposite directions.

19. The assembly of claim 18, wherein the at least two leadwires comprise TIP and RING leadwires for the active implantable medical device.

20. The assembly of claim 1, including a cancellation antenna extending through the lossy ferrite inductor in non-conductive relation.

21. The assembly of claim 1, including a feedthrough filter capacitor having a first set of electrode plates conductively coupled to at least one of the leadwires, and a second set of electrode plates conductively coupled to a housing, ferrule or ground plane of the active implantable medical device.

22. The assembly of claim 21, wherein the assembly forms an “

L”

, “

Pi”

, “

T”

, “

LL”

, “

5 element”

or higher order “

n element”

low pass filter circuit.

23. The assembly of claim 21, wherein the lossy ferrite inductor is bonded to the capacitor to form a beam-like structure.

24. The assembly of claim 21, wherein the capacitor and the lossy ferrite inductor are at least partially housed within a ferrule.

25. The assembly of claim 24, including an insulative cap disposed over the lossy ferrite inductor opposite the capacitor.

26. The assembly of claim 21, including a second lossy ferrite inductor through which the leadwires extend in non-conductive relation, wherein the lossy ferrite inductors are disposed on opposite sides of the capacitor.

27. The assembly of claim 21 wherein the capacitor is disposed on a body fluid side of the feedthrough terminal assembly.

28. The assembly of claim 21, wherein the feedthrough capacitor comprises first and second feedthrough capacitors associated with the lossy ferrite inductor.

29. The assembly of claim 28, wherein the first and second feedthrough capacitors are disposed adjacent to opposite surfaces of the lossy ferrite inductor.

30. The assembly of claim 29, wherein at least one of the capacitors is internally grounded.

31. The assembly of claim 28, wherein the first and second capacitors each include a first set of electrode plates conductively coupled to at least one of the leadwires, and a second set of electrode plates conductively coupled to the AIMD housing, ferrule, or ground plane.

32. The assembly of claim 31, wherein the first capacitor comprises an externally grounded capacitor, and the second capacitor comprises an internally grounded capacitor, the feedthrough terminal assembly further including a conductive material extending through both the first and second feedthrough capacitors to conductively couple the second set of electrode plates of the second capacitor with the second set of electrode plates of the first capacitor.

33. The assembly of claim 21, wherein the capacitor'"'"'s second set of electrode plates are externally grounded to and conductively coupled to the AIMD housing, ferrule or ground plane.

34. The assembly of claim 21, wherein the capacitor'"'"'s second set of electrode plates are internally grounded and conductively coupled to the AIMD housing, ferrule, or ground plane.

35. The assembly of claim 28, wherein the lossy ferrite inductor comprises first and second lossy ferrite inductors arranged, with the capacitors, to form an “

LL”

, “

5 element”

or “

n element”

low pass filter circuit, whereby the first inductor is disposed on the body fluid side of the first capacitor, and the second inductor is disposed between the first and second capacitors.

36. The assembly of claim 35, wherein the inductance of the first inductor is relatively large in comparison with the second inductor, and the capacitance of the first capacitor is relatively small in comparison with the second capacitor.

37. The assembly of claim 35, wherein the inductance of the first inductor is relatively small in comparison with the second inductor, and the capacitance of the first capacitor is relatively large in comparison with the second capacitor.

38. The assembly of claim 1, wherein the lossy ferrite inductor is disposed on a body fluid side of the feedthrough assembly as part of an “

L”

, “

L₂”

, “

T”

, “

LL”

, “

5 element”

or “

n element”

low pass filter circuit.

39. The assembly of claim 1, including a wire bond pad conductively coupled to at least one of the leadwires.

40. The assembly of claim 1, wherein a surface of the inductor is configured to form a tortuous path between at least one of the leadwires and an adjacent conductor.

41. A feedthrough terminal assembly for an active implantable medical device (AIMD), comprising:

a feedthrough capacitor having first and second sets of electrode plates;

a first conductive leadwire extending through the capacitor and conductively coupled to the first set of electrode plates;

a second conductive leadwire extending through the capacitor and conductively coupled to the second set of electrode plates; and

a lossy ferrite inductor associated with the capacitor and through which the leadwires extend in non-conductive relation, a surface of the inductor being configured to form a tortuous path between at least one of the leadwires and an adjacent conductor.

42. The assembly of claim 41, wherein the assembly forms an “

L”

, “

T”

“

LL”

, “

5 element”

or “

n element”

EMI filter circuit.

43. The assembly of claim 41, wherein the lossy ferrite inductor increases the impedence of the leadwires at selected RF frequencies and reduces magnetic flux core saturation of the lossy ferrite inductor through phase cancellation of signals carried by the leadwires.

44. The assembly of claim 41, wherein the active implantable medical device comprises a cardiac pacemaker, an implantable defibrillator, a congestive heart failure device, a hearing implant, a neurostimulator, a drug pump, a ventricular assist device, an insulin pump, a spinal cord stimulator, an implantable sensing system, an artificial heart, an incontinence device, a bone growth stimulator, a gastric pacemaker or a prosthetic device.

45. The assembly of claim 41, wherein the first leadwire extends from the electronic circuitry of the AIMD through a housing of the AIMD to a point within a human body, and the second leadwire is conductively coupled to at least a portion of the AIMD housing and the AIMD circuitry.

46. The assembly of claim 41, including a conformal coating over the lossy ferrite inductor, wherein the conformal coating comprises Paralene C, D, E, or N.

47. The assembly of claim 41, including an insulator disposed between the lossy ferrite inductor and the leadwires.

48. The assembly of claim 41, including one or more additional lossy ferrite inductors through which the leadwires extend in non-conductive relation.

49. The assembly of claim 48, wherein the lossy ferrite inductors are disposed adjacent to one another.

50. The assembly of claim 49, wherein the lossy ferrite inductors are each comprised of materials having different physical or electrical properties.

51. The assembly of claim 48, including a hermetic insulator disposed between the leadwires and a ferrule, wherein the lossy ferrite inductors are disposed on opposite sides of the insulator.

52. The assembly of claim 41, including a hermetic insulator disposed between the leadwires and a ferrule, wherein the lossy ferrite inductor is bonded to the insulator to form a beam-like structure.

53. The assembly of claim 41, wherein the lossy ferrite inductor includes an aperture through which a leak detection gas can be detected.

54. The assembly of claim 41, wherein at least one of the leadwires is wound about the lossy ferrite inductor to form multiple turns, and wherein adjacent portions of the wound leadwire are electrically insulated from one another.

55. The assembly of claim 54, wherein the lossy ferrite inductor includes a notch for receiving the wound leadwire.

56. The assembly of claim 54, wherein the lossy ferrite inductor includes multiple notches therein.

57. The assembly of claim 54, wherein at least two leadwires are wound about the lossy ferrite inductor to form one or more turns, and wherein the turn count for the at least two leadwires is not equal.

58. The assembly of claim 41, including means for maintaining the lossy ferrite inductor in close association with the AIMD without laminating or bonding the inductor to another component.

59. The assembly of claim 58, wherein the maintaining means comprises a mechanical lock, a deformation in the leadwire, a cured polymer, or a wire bond pad attached to the leadwire.

60. The assembly of claim 41, wherein at least two of the leadwires are routed through the lossy ferrite inductor in opposite directions.

61. The assembly of claim 60, wherein the at least two leadwires comprise TIP and RING leadwires for the active implantable medical device.

62. The assembly of claim 41, including a cancellation antenna extending through the lossy ferrite inductor in non-conductive relation.

63. The assembly of claim 41, wherein the lossy ferrite inductor is bonded to the capacitor to form a beam-like structure.

64. The assembly of claim 41, wherein the capacitor and the lossy ferrite inductor are at least partially housed within a ferrule.

65. The assembly of claim 64, including an insulative cap disposed over the lossy ferrite inductor opposite the capacitor.

66. The assembly of claim 41, including a second lossy ferrite inductor through which the leadwires extend in non-conductive relation, wherein the lossy ferrite inductors are disposed on opposite sides of the capacitor.

67. The assembly of claim 41 wherein the capacitor is disposed on a body fluid side of the feedthrough terminal assembly.

68. The assembly of claim 41, wherein the feedthrough capacitor comprises first and second feedthrough capacitors associated with the lossy ferrite inductor.

69. The assembly of claim 68, wherein the first and second feedthrough capacitors are disposed adjacent to opposite surfaces of the lossy ferrite inductor.

70. The assembly of claim 69, wherein at least one of the capacitors is internally grounded.

71. The assembly of claim 68, wherein the first and second capacitors each include a first set of electrode plates conductively coupled to at least one of the leadwires, and a second set of electrode plates conductively coupled to the AIMD housing, ferrule, or ground plane.

72. The assembly of claim 71, wherein the first capacitor comprises an externally grounded capacitor, and the second capacitor comprises an internally grounded capacitor, the feedthrough terminal assembly further including a conductive material extending through both the first and second feedthrough capacitors to conductively couple the second set of electrode plates of the second capacitor with the second set of electrode plates of the first capacitor.

73. The assembly of claim 68, wherein the lossy ferrite inductor comprises first and second lossy ferrite inductors arranged, with the capacitors, to form an “

LL”

, “

5 element”

or “

n element”

low pass filter circuit, whereby the first inductor is disposed on the body fluid side of the first capacitor, and the second inductor is disposed between the first and second capacitors.

74. The assembly of claim 73, wherein the inductance of the first inductor is relatively large in comparison with the second inductor, and the capacitance of the first capacitor is relatively small in comparison with the second capacitor.

75. The assembly of claim 73, wherein the inductance of the first inductor is relatively small in comparison with the second inductor, and the capacitance of the first capacitor is relatively large in comparison with the second capacitor.

76. The assembly of claim 41, wherein the capacitor'"'"'s second set of electrode plates are externally grounded to and conductively coupled to an AIMD housing, ferrule or ground plane.

77. The assembly of claim 41, wherein the capacitor'"'"'s second set of electrode plates are internally grounded and conductively coupled to an AIMD housing, ferrule, or ground plane.

78. The assembly of claim 41, wherein the lossy ferrite inductor is disposed on a body fluid side of the feedthrough assembly as part of an “

L”

, “

L₂”

, “

T”

, “

LL”

, “

5 element”

or “

n element”

low pass filter circuit.

79. The assembly of claim 41, including a wire bond pad conductively coupled to at least one of the leadwires.

80. A feedthrough terminal assembly for an active implantable medical device (AIMD), comprising:

a feedthrough capacitor having first and second sets of electrode plates, the second set of electrode plates being conductively coupled to a housing, ferrule or ground plane of the AIMD;

a lossy ferrite inductor closely associated with the capacitor;

a first conductive leadwire extending through the capacitor and the lossy ferrite inductor, the first leadwire extending through the lossy ferrite inductor in non-conductive relation and conductively coupled to the first set of electrode plates; and

a second conductive leadwire extending through the lossy ferrite inductor in non-conductive relation and in an opposite direction in comparison with the first conductive leadwire.

81. The assembly of claim 80, wherein the lossy ferrite inductor increases the impedence of the leadwires at selected RF frequencies and reduces magnetic flux core saturation of the lossy ferrite inductor through phase cancellation of signals carried by the leadwires.

82. The assembly of claim 81, wherein a surface of the inductor is configured to form a tortuous path between at least one of the leadwires and an adjacent conductor.

83. The assembly of claim 80, wherein the active implantable medical device comprises a cardiac pacemaker, an implantable defibrillator, a congestive heart failure device, a hearing implant, a neurostimulator, a drug pump, a ventricular assist device, an insulin pump, a spinal cord stimulator, an implantable sensing system, an artificial heart, an incontinence device, a bone growth stimulator, a gastric pacemaker or a prosthetic device.

84. The assembly of claim 80, wherein the first leadwire extends from the electronic circuitry of the AIMD through the housing of the AIMD to a point within a human body, and the second leadwire is conductively coupled to at least a portion of the AIMD housing and the AIMD circuitry.

85. The assembly of claim 80, including a conformal coating over the lossy ferrite inductor, wherein the conformal coating comprises Paralene C, D, E, or N.

86. The assembly of claim 80, including an insulator disposed between the lossy ferrite inductor and the leadwires.

87. The assembly of claim 80, including one or more additional lossy ferrite inductors through which the leadwires extend in non-conductive relation.

88. The assembly of claim 87, wherein the lossy ferrite inductors are disposed adjacent to one another.

89. The assembly of claim 88, wherein the lossy ferrite inductors are each comprised of materials having different physical or electrical properties.

90. The assembly of claim 87, including a hermetic insulator disposed between the leadwires and a ferrule, wherein the lossy ferrite inductors are disposed on opposite sides of the insulator.

91. The assembly of claim 80, including a hermetic insulator disposed between the leadwires and a ferrule, wherein the lossy ferrite inductor is bonded to the insulator to form a beam-like structure.

92. The assembly of claim 80, wherein the lossy ferrite inductor includes an aperture through which a leak detection gas can be detected.

93. The assembly of claim 80, wherein at least one of the leadwires is wound about the lossy ferrite inductor to form multiple turns, and wherein adjacent portions of the wound leadwire are electrically insulated from one another.

94. The assembly of claim 93, wherein the lossy ferrite inductor includes a notch for receiving the wound leadwire.

95. The assembly of claim 93, wherein the lossy ferrite inductor includes multiple notches therein.

96. The assembly of claim 93, wherein at least two leadwires are wound about the lossy ferrite inductor to form one or more turns, and wherein the turn count for the at least two leadwires is not equal.

97. The assembly of claim 80, including means for maintaining the lossy ferrite inductor in close association with the AIMD without laminating or bonding the inductor to another component.

98. The assembly of claim 97, wherein the maintaining means comprises a mechanical lock, a deformation in the leadwire, a cured polymer, or a wire bond pad attached to the leadwire.

99. The assembly of claim 80, wherein the at least two leadwires comprise TIP and RING leadwires for the active implantable medical device.

100. The assembly of claim 80, including a cancellation antenna extending through the lossy ferrite inductor in non-conductive relation.

101. The assembly of claim 80, wherein the assembly forms an “

L”

, “

Pi”

, “

T”

, “

LL”

, “

5 element”

or higher order “

n element”

low pass filter circuit.

102. The assembly of claim 80, wherein the lossy ferrite inductor is bonded to the capacitor to form a beam-like structure.

103. The assembly of claim 80, wherein the capacitor and the lossy ferrite inductor are at least partially housed within a ferrule.

104. The assembly of claim 103, including an insulative cap disposed over the lossy ferrite inductor opposite the capacitor.

105. The assembly of claim 80, including a second lossy ferrite inductor through which the leadwires extend in non-conductive relation, wherein the lossy ferrite inductors are disposed on opposite sides of the capacitor.

106. The assembly of claim 80 wherein the capacitor is disposed on a body fluid side of the feedthrough terminal assembly.

107. The assembly of claim 80, wherein the feedthrough capacitor comprises first and second feedthrough capacitors associated with the lossy ferrite inductor.

108. The assembly of claim 107, wherein the first and second feedthrough capacitors are disposed adjacent to opposite surfaces of the lossy ferrite inductor.

109. The assembly of claim 108, wherein at least one of the capacitors is internally grounded.

110. The assembly of claim 107, wherein the first and second capacitors each include a first set of electrode plates conductively coupled to at least one of the leadwires, and a second set of electrode plates conductively coupled to the AIMD housing, ferrule, or ground plane.

111. The assembly of claim 110, wherein the first capacitor comprises an externally grounded capacitor, and the second capacitor comprises an internally grounded capacitor, the feedthrough terminal assembly further including a conductive material extending through both the first and second feedthrough capacitors to conductively couple the second set of electrode plates of the second capacitor with the second set of electrode plates of the first capacitor.

112. The assembly of claim 80, wherein the capacitor'"'"'s second set of electrode plates are externally grounded to and conductively coupled to the AIMD housing, ferrule or ground plane.

113. The assembly of claim 80, wherein the capacitor'"'"'s second set of electrode plates are internally grounded and conductively coupled to the AIMD housing, ferrule, or ground plane.

114. The assembly of claim 107, wherein the lossy ferrite inductor comprises first and second lossy ferrite inductors arranged, with the capacitors, to form an “

LL₁”

, “

5 element”

or “

n element”

low pass filter circuit, whereby the first inductor is disposed on the body fluid side of the first capacitor, and the second inductor is disposed between the first and second capacitors.

115. The assembly of claim 114, wherein the inductance of the first inductor is relatively large in comparison with the second inductor, and the capacitance of the first capacitor is relatively small in comparison with the second capacitor.

116. The assembly of claim 114, wherein the inductance of the first inductor is relatively small in comparison with the second inductor, and the capacitance of the first capacitor is relatively large in comparison with the second capacitor.

117. The assembly of claim 80, wherein the lossy ferrite inductor is disposed on a body fluid side of the feedthrough assembly as part of an “

L”

, “

L₂”

, “

T”

, “

LL”

, “

5 element”

or “

n element”

low pass filter circuit.

118. The assembly of claim 80, including a wire bond pad conductively coupled to at least one of the leadwires.

119. A process for filtering electromagnetic interference (EMI) in an implanted leadwire extending from an active implantable medical device (AIMD) into body fluids or tissue, the leadwire being subjected to occasional high power electromagnetic fields such as those produced by medical diagnostic equipment including magnetic resonance imaging, comprising the steps of:

passing the leadwire through an inductive and resistive low pass filter element to increase EMI protection of AIMD electronics and to raise the input impedance of the AIMD circuitry thereby reducing currents induced in the implanted leadwire by the occasional high power electromagnetic fields, wherein the inductive and resistive low pass filter element has a diameter to thickness ratio of at least 1;

1.

120. The process of claim 119, wherein the active implantable medical device comprises a cardiac pacemaker, an implantable defibrillator, a congestive heart failure device, a hearing implant, a neurostimulator, a drug pump, a ventricular assist device, an insulin pump, a spinal cord stimulator, an implantable sensing system, an artificial heart, an incontinence device, a bone growth stimulator, a gastric pacemaker, or a prosthetic device.

121. The process of claim 119, including the step of placing the inductive and resistive low pass filter element on a body fluid side of a feedthrough assembly as part of an “

L”

, “

L₂”

, “

T”

, “

LL”

, “

5 element”

or “

n element”

low pass filter circuit.

122. The process of claim 119, including the step of conductively coupling a wire bond pad to the leadwire.

123. The process of claim 119, including the step of forming a tortuous path on a surface of the inductive and resistive low pass filter element between the leadwire and an adjacent conductor.

124. The process of claim 119, including the step of coating the inductive and resistive low pass filter element with a Paralene C, D, E, or N material.

125. The process of claim 119, including the step of placing an insulator between the inductive and resistive low pass filter element and the leadwire.

126. The process of claim 119, including the step of passing the leadwire through one or more additional inductive and resistive low pass filter elements.

127. The process of claim 126, including the step of disposing the inductive and resistive low pass filter elements adjacent to one another.

128. The process of claim 127, wherein the inductive and resistive low pass filter elements are each comprised of materials having different physical or electrical properties.

129. The process of claim 126, including the step of placing a hermetic insulator between the leadwire and a ferrule such that the inductive and resistive low pass filter elements are disposed on opposite sides of the insulator.

130. The process of claim 119, including the step of placing a hermetic insulator between the leadwire and a ferrule, and bonding the inductive and resistive low pass filter element to the insulator to form a beam-like structure.

131. The process of claim 119, including the step of providing an aperture through the inductive and resistive low pass filter element through which a leak detection gas can be detected.

132. The process of claim 119, including the step of winding the leadwire about the inductive and resistive low pass filter element to form multiple turns.

133. The process of claim 119, including the step of maintaining the inductive and resistive low pass filter element in close association with the AIMD without laminating or bonding the inductive and resistive low pass filter element to another component.

134. The process of claim 119, including the step of passing a second leadwire through the inductive and resistive low pass filter element to increase EMI protection of the AIMD electronics and to raise the input impedence of the AIMD circuitry thereby reducing currents induced in the implanted leadwires by the occasional high power electromagnetic fields.

135. The process of claim 134, including the steps of extending the first leadwire from the AIMD circuitry through a housing of the AIMD to a point within a human body, and conductively coupling the second leadwire to at least a portion of the AIMD housing and the AIMD circuitry.

136. The process of claim 134, including the step of winding the leadwires about the inductive and resistive low pass filter element such that the turn count for the leadwires relative to one another is not equal.

137. The process of claim 134, including the step of routing the leadwires through the inductive and resistive low pass filter element in opposite directions.

138. The process of claim 134, including the step of passing a cancellation antenna through the inductive and resistive low pass filter element.

139. The process of claim 134, including the step of conductively coupling at least one of the leadwires to a first set of electrode plates of a feedthrough filter capacitor, and conductively coupling a second set of electrode plates of the feedthrough filter capacitor to a housing, ferrule or ground plane of the active implantable medical device.

140. The process of claim 139, including the step forming an “

L”

, “

Pi”

, “

T”

, “

LL”

, “

5 element”

or higher order “

n element”

low pass filter circuit.

141. The process of claim 139, including the step of bonding the capacitor to the inductive and resistive low pass filter element to form a beam-like structure.

142. The process of claim 139, including the step of at least partially housing the capacitor and the inductive and resistive low pass filter element within the ferrule.

143. The process of claim 142, including the step of placing an insulative cap over the inductive and resistive low pass filter element opposite the capacitor.

144. The process of claim 139, including the step of passing the leadwires through a second inductive and resistive low pass filter element in non-conductive relation, and disposing the inductive and resistive low pass filter elements on opposite sides of the capacitor.

145. The process of claim 139, including the step of placing the capacitor on a body fluid side of a feedthrough terminal assembly.

146. The process of claim 139, including the step of associating a second feedthrough capacitor with the inductive and resistive low pass filter element.

147. The process of claim 146, including the step of placing the feedthrough capacitors adjacent to opposite sides of the inductive and resistive low pass filter element.

148. The process of claim 147, including the step of internally grounding at least one of the capacitors.

149. The process of claim 147, including the steps of conductively coupling at least one of the leadwires to first sets of electrode plates within the capacitors, and conductively coupling second sets of electrode plates within the capacitors to the AIMD housing, ferrule or ground plane.

150. The process of claim 149, including the steps of externally grounding one of the capacitors and internally grounding another one of the capacitors.

151. The process of claim 146, including the steps of placing a first inductive and resistive low pass filter element on a body fluid side of the first capacitor, and placing a second inductive and resistive low pass filter element between the first and second capacitors to form an “

LL₁”

, “

5 element”

or “

n element”

low pass filter circuit.

152. The process of claim 151, wherein the inductance of the first inductive and resistive low pass filter element is relatively large in comparison with the second inductive and resistive low pass filter element, and the capacitance of the first capacitor is relatively small in comparison with the second capacitor, to protect the AIMD circuitry from ring-back of energy from either of the feedthrough capacitors induced by occasional high power electromagnetic fields or signals.

153. A process for filtering electromagnetic interference (EMI) in a plurality of leadwires extending from an active implantable medical device (AIMD) to different points within a human body, comprising the steps of:

passing the leadwires through a common inductive element to increase the impedence of the leadwires at selected RF frequencies and reduce magnetic flux core saturation of the inductive element through phase cancellation of signals carried by the leadwires.

154. The process of claim 153, including the step of placing the inductive element on a body fluid side of a feedthrough assembly as part of an “

L”

, “

L₂”

, “

T”

, “

LL”

, “

5 element”

or “

n element”

low pass filter circuit.

155. The process of claim 154, wherein the active implantable medical device comprises a cardiac pacemaker, an implantable defibrillator, a congestive heart failure device, a hearing implant, a neurostimulator, a drug pump, a ventricular assist device, an insulin pump, a spinal cord stimulator, an implantable sensing system, an artificial heart, an incontinence device, a bone growth stimulator, a gastric pacemaker, or a prosthetic device.

156. The process of claim 154, including the step of forming a tortuous path on a surface of the inductive element between at least one of the leadwires and an adjacent conductor.

157. The process of claim 154, wherein the leadwires are subjected to occasional high power electromagnetic fields such as those produced by medical diagnostic equipment including magnetic resonance imaging, and wherein the inductive element has a diameter to thickness ratio of at least 1:

1.

158. The process of claim 153, including the step of conductively coupling a wire bond pad to at least one of the leadwires.

159. The process of claim 153, including the step of coating the inductive element with a Paralene C, D, E, or N material.

160. The process of claim 153, including the step of placing an insulator between the inductive element and at least one of the leadwires.

161. The process of claim 153, including the step of passing the leadwires through one or more additional inductive elements.

162. The process of claim 161, including the step of disposing the inductive elements adjacent to one another.

163. The process of claim 162, wherein the inductive elements are each comprised of materials having different physical or electrical properties.

164. The process of claim 161, including the step of placing a hermetic insulator between the leadwires and a ferrule such that the inductive elements are disposed on opposite sides of the insulator.

165. The process of claim 153, including the step of placing a hermetic insulator between the leadwires and a ferrule, and bonding the inductive element to the insulator to form a beam-like structure.

166. The process of claim 153, including the step of providing an aperture through the inductive element through which a leak detection gas can be detected.

167. The process of claim 153, including the step of winding at least one of the leadwires about the inductive element to form multiple turns.

168. The process of claim 153, including the step of maintaining the inductive element in close association with the AIMD without laminating or bonding the inductive element to another component.

169. The process of claim 153, including the steps of extending a first leadwire from electronic circuitry of the AIMD through a housing of the AIMD to a point within a human body, and conductively coupling a second leadwire to at least a portion of the AIMD housing and the AIMD circuitry.

170. The process of claim 153, including the step of winding the leadwires about the inductive element such that the turn count for the leadwires relative to one another is not equal.

171. The process of claim 153, including the step of routing the leadwires through the inductive element in opposite directions.

172. The process of claim 153, including the step of passing a cancellation antenna through the inductive element.

173. The process of claim 153, including the step of conductively coupling at least one of the leadwires to a first set of electrode plates of a feedthrough capacitor, and conductively coupling a second set of electrode plates of the feedthrough capacitor to a housing, ferrule or ground plane of the active implantable medical device.

174. The process of claim 173, including the step forming an “

L”

, “

Pi”

, “

T”

, “

LL”

, “

5 element”

or higher order “

n element”

low pass filter circuit.

175. The process of claim 173, including the step of bonding the capacitor to the inductive element to form a beam-like structure.

176. The process of claim 173, including the step of at least partially housing the capacitor and the inductive element within the ferrule.

177. The process of claim 176, including the step of placing an insulative cap over the inductive element opposite the capacitor.

178. The process of claim 173, including the step of passing the leadwires through a second inductive element in non-conductive relation, and disposing the inductive elements on opposite sides of the capacitor.

179. The process of claim 173, including the step of placing the capacitor on a body fluid side of a feedthrough terminal assembly.

180. The process of claim 173, including the step of associating a second feedthrough capacitor with the inductive element.

181. The process of claim 180, including the step of placing the feedthrough capacitors adjacent to opposite sides of the inductive element.

182. The process of claim 181, including the step of internally grounding at least one of the capacitors.

183. The process of claim 181, including the steps of conductively coupling at least one of the leadwires to first sets of electrode plates within the capacitors, and conductively coupling second sets of electrode plates within the capacitors to the AIMD housing, ferrule or ground plane.

184. The process of claim 183, including the steps of externally grounding one of the capacitors and internally grounding another one of the capacitors.

185. The process of claim 180, including the steps of placing a first inductive element on a body fluid side of the first capacitor, and placing a second inductive element between the first and second capacitors to form an “

LL₁”

, “

5 element”

or “

n element”

low pass filter circuit.

186. The process of claim 185, wherein the inductance of the first inductive element is relatively large in comparison with the second inductive element, and the capacitance of the first capacitor is relatively small in comparison with the second capacitor, to protect the AIMD circuitry from ring-back of energy from either of the feedthrough capacitors induced by occasional high power electromagnetic fields or signals.

187. A process for filtering electromagnetic signals in a plurality of leadwires extending from an active implantable medical device (AIMD) into body fluids or tissue, the leadwires being subjected to occasional high power electromagnetic fields or signals generated either by AIMD circuitry or external sources such as medical diagnostic equipment including magnetic resonance imaging (MRI), comprising the steps of:

conductively coupling the leadwires to respective sets of electrode plates within a feedthrough capacitor optimized for electromagnetic interference (EMI) filtering; and

passing the leadwires through a common inductive element disposed adjacent to the feedthrough capacitor and between the AIMD circuitry and the feedthrough capacitor, for decoupling signals induced on the leadwires by the occasional high power electromagnetic fields or signals generated either by AIMD circuitry or external sources, from the feedthrough capacitor, to protect the AIMD circuitry from ring-back of energy from the feedthrough capacitor induced by the occasional high power electromagnetic fields or signals.

188. The process of claim 187, wherein the active implantable medical device comprises a cardiac pacemaker, an implantable defibrillator, a congestive heart failure device, a hearing implant, a neurostimulator, a drug pump, a ventricular assist device, an insulin pump, a spinal cord stimulator, an implantable sensing system, an artificial heart, an incontinence device, a bone growth stimulator, a gastric pacemaker, or a prosthetic device.

189. The process of claim 187, including the step of placing the inductive element on a body fluid side of a feedthrough assembly as part of an “

L”

, “

L₂”

, “

T”

, “

LL₁”

, “

5 element”

or “

n element”

low pass filter circuit.

190. The process of claim 189, including the step of forming a tortuous path on a surface of the inductive element between at least one of the leadwires and an adjacent conductor.

191. The process of claim 187, including the step of conductively coupling a wire bond pad to at least one of the leadwires.

192. The process of claim 187, including the step of coating the inductive element with a Paralene C, D, E, or N material.

193. The process of claim 187, including the step of placing an insulator between the inductive element and at least one of the leadwires.

194. The process of claim 187, including the step of passing the leadwires through one or more additional inductive elements.

195. The process of claim 194, including the step of disposing the inductive elements adjacent to one another, wherein the inductive elements are each comprised of materials having different physical or electrical properties.

196. The process of claim 194, including the step of placing a hermetic insulator between the leadwires and a ferrule such that the inductive elements are disposed on opposite sides of the insulator.

197. The process of claim 187, including the step of placing a hermetic insulator between the leadwires and a ferrule, and bonding the inductive element to the insulator to form a beam-like structure.

198. The process of claim 187, including the step of providing an aperture through the inductive element through which a leak detection gas can be detected.

199. The process of claim 187, including the step of winding at least one of the leadwires about the inductive element to form multiple turns.

200. The process of claim 187, including the step of maintaining the inductive element in close association with the AIMD without laminating or bonding the inductive element to another component.

201. The process of claim 187, including the steps of extending a first leadwire from electronic circuitry of the AIMD through a housing of the AIMD to a point within a human body, and conductively coupling a second leadwire to at least a portion of the AIMD housing and the AIMD circuitry.

202. The process of claim 187, including the step of winding the leadwires about the inductive element such that the turn count for the leadwires relative to one another is not equal.

203. The process of claim 187, including the step of routing the leadwires through the inductive element in opposite directions.

204. The process of claim 187, including the step of passing a cancellation antenna through the inductive element.

205. The process of claim 187, including the step of bonding the capacitor to the inductive element to form a beam-like structure.

206. The process of claim 187, including the step of at least partially housing the capacitor and the inductive element within the ferrule.

207. The process of claim 206, including the step of placing an insulative cap over the inductive element opposite the capacitor.

208. The process of claim 187, including the step of passing the leadwires through a second inductive element in non-conductive relation, and disposing the inductive elements on opposite sides of the capacitor.

209. The process of claim 187, including the step of associating a second feedthrough capacitor with the inductive element.

210. The process of claim 209, including the step of placing the feedthrough capacitors adjacent to opposite sides of the inductive element.

211. The process of claim 210, including the step of internally grounding at least one of the capacitors.

212. The process of claim 210, including the steps of externally grounding one of the capacitors and internally grounding another one of the capacitors.

213. The process of claim 209, including the steps of placing a first inductive element on a body fluid side of the first capacitor, and placing a second inductive element between the first and second capacitors to form an “

LL₁”

, “

5 element”

or “

n element”

low pass filter circuit.

214. The process of claim 213, wherein the inductance of the first inductive element is relatively large in comparison with the second inductive element, and the capacitance of the first capacitor is relatively small in comparison with the second capacitor.