Implantable medical device for generating cardiac pressure-volume loop and optimizing therapy

• US 20070129765A1
• Filed: 12/07/2005
• Published: 06/07/2007
• Est. Priority Date: 12/07/2005
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Zhang, Yongxing, Wang, Sophia, Zhang, Yunlong, Gilkerson, James
• Granted Patent: US 7,580,746 B2
• Time in Patent Office: Days
• US Class Current: 607/18
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36564 controlled by blood pressure
• CPC Class Codes: A61N 1/36578 controlled by mechanical motion of the heart wall, e.g. measured by an accelerometer or microphone
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

An implantable medical device for generating a cardiac pressure-volume loop, the implantable medical device comprising a pulse generator including control circuitry, a first cardiac lead including a proximal end and a distal end and coupled to the pulse generator at the proximal end, a first electrode located at the distal end of the cardiac lead and operatively coupled to the control circuitry, a sound sensor operatively coupled to the control circuitry, and a pressure sensor operatively coupled to the control circuitry, wherein the implantable medical device is adapted for measuring intracardiac impedance. A method of using the implantable medical device to optimize therapy delivered to the heart.

Claims

1. An implantable medical device for generating a cardiac pressure-volume loop, the implantable medical device comprising:

a pulse generator including control circuitry;

a first cardiac lead including a proximal end and a distal end, the cardiac lead coupled to the pulse generator at the proximal end;

a first electrode located at the distal end of the cardiac lead and operatively coupled to the control circuitry;

a sound sensor operatively coupled to the control circuitry; and

a pressure sensor operatively coupled to the control circuitry;

wherein the implantable medical device is adapted for measuring an intracardiac impedance.

2. The implantable medical device of claim 1 further comprising a first coil coupled to the first cardiac lead and operatively coupled to the control circuitry, wherein the intracardiac impedance is measured between the first coil and the first electrode.

3. The implantable medical device of claim 1 further comprising a second electrode operatively coupled to the control circuitry, wherein the intracardiac impedance is measured between the first electrode and the second electrode.

4. The implantable medical device of claim 3, wherein the second electrode is located on the first cardiac lead.

5. The implantable medical device of claim 3 further comprising a second cardiac lead, wherein the second electrode is located on the second cardiac lead.

6. The implantable medical device of claim 1, wherein the sound sensor is located in the pulse generator.

7. The implantable medical device of claim 1, wherein the sound sensor is located on the first cardiac lead.

8. The implantable medical device of claim 1, wherein the first cardiac lead further includes a conductive member and the pressure sensor is located at the distal end of the cardiac lead and is operatively coupled to the control circuitry via the conductive member.

9. The implantable medical device of claim 1, wherein the pressure sensor is remote from the cardiac lead and is connected to the control circuitry via a second conductive member.

10. The implantable medical device of claim 1, wherein the implantable medical device is operatively coupled to an external device.

11. The implantable medical device of claim 10, wherein the implantable medical device is operatively coupled to the external device via a RF connection.

12. The implantable medical device of claim 10, wherein the external device is operatively coupled to a remote system.

13. A method of generating a pressure-volume loop for a heart using an implantable medical device including a pulse generator, control circuitry adapted for measuring cardiac volume, a cardiac lead having a proximal end and a distal end, an electrode coupled to the distal end of the cardiac lead, a sound sensor, and a pressure sensor, the method comprising:

creating a first corner of the pressure-volume loop by recording a first cardiac pressure and a first cardiac volume at a first time associated with an S1 heart sound;

creating a second corner of the pressure-volume loop by recording a second cardiac pressure and a second cardiac volume at a second time at which cardiac volume starts decreasing;

creating a third corner of the pressure-volume loop by recording a third cardiac pressure and a third cardiac volume at a third time associated with an S2 heart sound; and

creating a fourth corner of the pressure-volume loop by recording a fourth cardiac pressure and a fourth cardiac volume at a fourth time at which the cardiac volume increases rapidly.

14. The method of claim 13, wherein the cardiac volume is calculated based on an intracardiac impedance measured by the implantable medical device.

15. A method for modifying therapy delivered to a heart using an implantable medical device including a pulse generator, control circuitry adapted for measuring cardiac volume, a cardiac lead having a proximal end and a distal end, an electrode coupled to the distal end of the cardiac lead, a sound sensor, and a pressure sensor, the method comprising:

generating a baseline pressure-volume;

storing the baseline pressure-volume loop in the control circuitry;

generating a second pressure-volume loop at a specified interval;

comparing the second pressure-volume loop to the baseline pressure-volume loop to detect a change in a cardiac parameter; and

modifying the therapy delivered to the heart in response to the change.

16. The method of claim 15, wherein the cardiac volume is calculated based on an intracardiac impedance measured by the implantable medical device.

17. The method of claim 15 wherein the cardiac parameter is selected from the group consisting of a cardiac pressure, a cardiac volume, an ejection fraction, a derivative of cardiac pressure, and a derivative of cardiac volume.

18. The method of claim 15, wherein the cardiac parameter comprises ejection fraction and the change comprises a decrease in ejection fraction below 50%.

19. The method of claim 15, wherein the delivered therapy is selected from the group consisting of a pharmaceutical, a pacing therapy, and a defibrillation shock.

20. A method for modifying therapy delivered to a heart using an implantable medical device including a pulse generator, control circuitry adapted for measuring cardiac volume, a cardiac lead having a proximal end and a distal end, an electrode coupled to the distal end of the cardiac lead, a sound sensor, and a pressure sensor, the method comprising:

detecting an increase in a heart rate using the electrode;

generating a first pressure-volume loop;

determining whether fibrillation is occurring based on the first pressure-volume loop; and

delivering defibrillation therapy.

21. The method of claim 20 wherein the cardiac volume is calculated based on an intracardiac impedance measured by the implantable medical device.

22. The method of claim 20 wherein the method further includes generating a baseline pressure-volume loop using the implantable medical device, storing the baseline pressure volume loop in the control circuitry, and wherein the step of determining whether fibrillation is occurring includes comparing the first pressure-volume loop to the baseline pressure-volume loop.

23. The method of claim 20 wherein the detected increase in heart rate is an increase to between 120 to 165 beats per minute.