SYMPATHETIC STIMULATION FOR IMPROVED MYOCARDIAL RELAXATION

• US 20110190840A1
• Filed: 02/02/2011
• Published: 08/04/2011
• Est. Priority Date: 02/03/2010
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Alvarez, Guy, Shuros, Allan C., Arcot-Krishnamurthy, Shantha
• Granted Patent: US 8,498,704 B2
• Time in Patent Office: Days
• US Class Current: 607/19
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/36564 controlled by blood pressure

Abstract

Described are methods and devices for improving diastolic function with electrostimulation in heart failure patients who exhibit relatively normal systolic function. Such patients are characterized by impaired myocardial relaxation during diastole that prevents adequate filling of the ventricles during diastole to thereby reduce cardiac output. An implantable device is described for effecting strategic and periodic stimulation of the sympathetic nervous system to elicit myocardial adrenergic activation for improved myocardial relaxation.

Claims

1. A device, comprising:

neural stimulation circuitry for delivering electrostimulation pulses to one or more electrodes adapted for stimulating sympathetic nerves innervating the heart;

lusitropy sensing circuitry for connecting to a lusitropy sensor and measuring a lusitropy parameter during diastole selected from a rate of ventricular pressure decrease, a rate of ventricular force decrease, or ventricular isovolumic relaxation time; and

,

a controller programmed to compare the lusitropy parameter to a specified threshold in order to determine if diastolic relaxation is impaired and, if diastolic relaxation is impaired, enter a neural stimulation mode for operating the neural stimulation circuitry to deliver sympathetic stimulation to the heart.

2. The device of claim 1 further comprising cardiac sensing circuitry for connecting to one or more electrodes to sense cardiac electrical activity and wherein the controller is programmed to deliver sympathetic stimulation to the heart by operating the neural stimulation circuitry to deliver electrostimulation pulses during a cardiac refractory period occurring at specified time interval after a detected cardiac depolarization.

3. The device of claim 2 wherein the controller is programmed to vary the specified time interval for delivering electrostimulation pulses with heart rate.

4. The device of claim 1 further comprising:

air exertion level sensor selected from an accelerometer or a minute ventilation sensor;

wherein the neural stimulation circuitry is configured to deliver electrostimulation pulses either to an atrial stimulation channel configured to stimulate atrial sympathetic nerves or to a ventricular stimulation channel configured to stimulate ventricular sympathetic nerves; and

,

wherein, in the neural stimulation mode, the controller is programmed to deliver electrostimulation pulses through both the atrial and ventricular stimulation channels if the exertion level is above a specified threshold value and deliver electrostimulation pulses through only the ventricular stimulation channel if the exertion level is not above the specified threshold value.

5. The device of claim 4 wherein, in the neural stimulation mode, the controller is configured to deliver electrostimulation pulses through the ventricular stimulation channel on an intermittent basis to exert a conditioning effect if the exertion level is not above the specified threshold value.

6. The device of claim 1 wherein the controller is further programmed to adjust one or more neural stimulation parameters selected from a neural stimulation duty cycle, an electrostimulation pulse amplitude, or particular electrodes to which the neural stimulation is delivered in accordance with the measured lusitropy parameter.

7. The device of claim 1 further comprising an accelerometer adapted for subcutaneous disposition in order to detect skeletal muscle contraction and wherein the controller is programmed to adjust one or more neural stimulation parameters if skeletal muscle contraction is detected.

8. The device of claim 1 wherein the lusitropy sensing circuitry is configured to measure ventricular isovolumic relaxation time as indicated by an impedance sensor for measuring ventricular volume.

9. The device of claim 1 wherein the lusitropy sensing circuitry is configured to measure ventricular isovolumic relaxation time as the interval between aortic valve closure and mitral valve opening as detected by a heart sound sensor.

10. The device of claim 1 further comprising cardiac sensing circuitry for connecting to one or more electrodes to sense cardiac electrical activity and wherein the controller is programmed to measure heart rate during delivery of sympathetic stimulation and to discontinue the neural stimulation mode if the heart rate increases above a specified safety threshold value.

11. The device of claim 1 further comprising cardiac sensing circuitry for connecting to one or more electrodes to sense cardiac electrical activity and wherein the controller is programmed to measure heart rate during delivery of sympathetic stimulation and to continue delivery of sympathetic stimulation if no heart rate increase and no change in the lusitropy parameter occurs in response thereto.

12. A device, comprising:

neural stimulation circuitry for delivering electrostimulation pulses to one or more electrodes adapted for stimulating sympathetic nerves innervating the heart;

an exertion level sensor selected from an accelerometer or a minute ventilation sensor;

wherein the neural stimulation circuitry is configured to deliver electrostimulation pulses to an atrial stimulation channel configured to stimulate atrial sympathetic nerves and/or to a ventricular stimulation channel configured to stimulate ventricular sympathetic nerves;

a controller for operating the neural stimulation circuitry in a neural stimulation mode to deliver sympathetic stimulation to the heart; and

,

wherein, in the neural stimulation mode, the controller is programmed to deliver electrostimulation pulses through both the atrial and ventricular stimulation channels if the exertion level is above a specified threshold value and deliver electrostimulation pulses through only the ventricular stimulation channel if the exertion level is not above the specified threshold value.

13. The device of claim 12 further comprising cardiac sensing circuitry for connecting to one or more electrodes to sense cardiac electrical activity and wherein, in the neural stimulation mode, the controller is programmed to operate the neural stimulation circuitry to deliver electrostimulation pulses during a cardiac refractory period occurring at specified time interval after a detected cardiac depolarization.

14. The device of claim 13 wherein the controller is programmed to vary the specified time interval for delivering electrostimulation pulses with heart rate.

15. The device of claim 12 wherein, in the neural stimulation mode, the controller is configured to deliver electrostimulation pulses through the ventricular stimulation channel on an intermittent basis to exert a conditioning effect if the exertion level is not above the specified threshold value.

16. The device of claim 12 further comprising:

lusitropy sensing circuitry for connecting to a lusitropy sensor and measuring a lusitropy parameter during diastole selected from a rate of ventricular pressure decrease, a rate of ventricular force decrease, or ventricular isovolumic relaxation time; and

,

wherein controller programmed to compare the lusitropy parameter to a specified threshold in order to determine if diastolic relaxation is impaired and, if diastolic relaxation is impaired, enter the neural stimulation mode for operating the neural stimulation circuitry to deliver sympathetic stimulation to the heart.

17. A method, comprising:

neural stimulation circuitry for delivering electrostimulation pulses to one or more electrodes adapted for stimulating sympathetic nerves innervating the heart;

an exertion level sensor selected from an accelerometer or a minute ventilation sensor;

wherein the neural stimulation circuitry is configured to deliver electrostimulation pulses to an atrial stimulation channel configured to stimulate atrial sympathetic nerves and/or to a ventricular stimulation channel configured to stimulate ventricular sympathetic nerves;

a controller for operating the neural stimulation circuitry in a neural stimulation mode to deliver sympathetic stimulation to the heart; and

,

wherein, in the neural stimulation mode, the controller is programmed to deliver electrostimulation pulses through both the atrial and ventricular stimulation channels if the exertion level is above a specified threshold value and deliver electrostimulation pulses through only the ventricular stimulation channel if the exertion level is not above the specified threshold value.

18. The method of claim 17 further comprising:

sensing cardiac electrical activity; and

,

delivering electrostimulation pulses during a cardiac refractory period occurring at specified time interval after a detected cardiac depolarization.

19. The method of claim 18 further comprising varying the specified time interval for delivering electrostimulation pulses with heart rate.

20. The method of claim 17 further comprising delivering electrostimulation pulses through the ventricular stimulation channel on an intermittent basis to exert a conditioning effect if the exertion level is not above the specified threshold value.