Cardiac resynchronization therapy diagnostics

1. System comprising:

a pacing device configured to be implanted within a patient, the pacing device comprising:

a plurality of electrodes;

signal generation circuitry configured to deliver ventricular pacing pulses for the cardiac resynchronization via the plurality of electrodes; and

a sensor configured to produce a mechanical motion signal representative of mechanical motion of the heart;

processing circuitry configured to:

for each of a plurality of cardiac cycles during which the pacing device delivered one of the ventricular pacing pulses, identify one or more features of a cardiac contraction within the mechanical motion signal during the cardiac cycle;

for each of the plurality of cardiac cycles, determine whether the cardiac contraction is a fusion beat based on the one or more features; and

determine a value of at least one metric indicating the effectiveness of the CRT based on the determinations of whether the cardiac contractions are fusion beats; and

a user interface configured to present the value of the at least one metric to a user.

2. The system of claim 1 , wherein the pacing device comprises a housing configured for implantation on or within the heart, wherein at least one of the signal generation circuitry and the sensor are within the housing.

3. The system of claim 1 , wherein the ventricular pacing is delivered to a left ventricle.

4. The system of claim 1 , wherein the sensor comprises a three-dimensional accelerometer.

5. The system of claim 1 , wherein the one or more features of the cardiac contraction within the mechanical motion signal comprise one or more of a slope of the mechanical motion signal during the cardiac contraction, an amplitude of the mechanical motion signal during the contraction, a maximum of the mechanical motion signal during the cardiac contraction, a minimum of the mechanical motion signal during the cardiac contraction, a ratio of the maximum and the minimum during the cardiac contraction, or a polarity of the mechanical motion signal during the cardiac contraction.

6. The system of claim 1 , wherein the one or more features of the cardiac contraction within the mechanical motion signal comprise one or more of an amount or a direction of motion relative to a point of origin during the contraction.

7. The system of claim 6 , wherein the one or more features of the cardiac contraction within the mechanical motion signal comprise an amount of motion in at least one direction other than a primary axis of motion during the cardiac contraction.

8. The system of claim 6 , wherein the one or more features of the cardiac contraction within the mechanical motion signal comprise an amount of motion in at least one plane orthogonal to a primary axis of motion during the cardiac contraction.

9. The system of claim 1 , wherein the one or more features of the cardiac contraction within the mechanical motion signal comprise one or more values resulting from comparison of the mechanical motion signal during the cardiac contraction to one or more templates.

10. The system of claim 9 , wherein the one or more templates comprise one or more of an intrinsic beat template, a fully-paced beat template, or a fusion beat template.

11. The system of claim 1 , wherein the value of at least one of the metrics indicates an amount of the contractions that were fusion beats.

12. The system of claim 11 , wherein the amount is a percentage of the contractions.

13. The system of claim 1 , wherein the processing circuitry comprises processing circuitry within the pacing device.

14. The system of claim 1 , further comprising another implantable medical device, wherein the another implantable medical device is configured to:

detect an atrial event; and

transmit a signal to the pacing device to control the pacing device to deliver the ventricular pacing pulse in response to the detection of the atrial event, wherein the processing circuitry comprises processing circuitry of the other implantable medical device.

15. The system of claim 1 , further comprising an external device configured to communicate with the pacing device, the external device comprising the user interface, wherein the processing circuitry comprises processing circuitry of the external device.

16. A method for determining the effectiveness of cardiac resynchronization therapy (CRT) by a pacing device, the method comprising, by processing circuitry of a medical device system comprising the pacing device:

receiving a mechanical motion signal from a sensor of the pacing device, the mechanical motion signal representative of mechanical motion of a heart;

for each of a plurality of cardiac cycles during which the pacing device delivered a ventricular pacing pulse for the CRT, identifying one or more features of a cardiac contraction within the mechanical motion signal during the cardiac cycle;

for each of the plurality of cardiac cycles, determining whether the cardiac contraction is a fusion beat based on the one or more features;

determining a value of at least one metric indicating the effectiveness of the CRT based on the determinations of whether the cardiac contractions are fusion beats; and

presenting the value of the at least one metric to a user via a user interface.

17. The method of claim 16 , wherein the pacing device comprises a housing configured for implantation on or within the heart, wherein the sensor is within the housing.

18. The method of claim 16 , wherein the ventricular pacing pulses are delivered to a left ventricle.

19. The method of claim 16 , wherein the sensor comprises a three-dimensional accelerometer.

20. The method of claim 16 , wherein the one or more features of the cardiac contraction comprise one or more of a slope of the mechanical motion signal during the cardiac contraction, an amplitude of the mechanical motion signal during the contraction, a maximum of the mechanical motion signal during the cardiac contraction, a minimum of the mechanical motion signal during the cardiac contraction, a ratio of the maximum and the minimum during the cardiac contraction, or a polarity of the mechanical motion signal during the cardiac contraction.

21. The method of claim 16 , wherein the one or more features of the cardiac contraction within the mechanical motion signal comprise one or more of an amount or a direction of motion relative to a point of origin during the contraction.

22. The method of claim 21 , wherein the one or more features of the cardiac contraction within the mechanical motion signal comprise an amount of motion in at least one direction other than a primary axis of motion during the cardiac contraction.

23. The method of claim 21 , wherein the one or more features of the cardiac contraction within the mechanical motion signal comprise an amount of motion in at least one plane orthogonal to a primary axis of motion during the cardiac contraction.

24. The method of claim 16 , wherein the one or more features of the cardiac contraction within the mechanical motion signal comprise one or more values resulting from comparison of the mechanical motion signal during the cardiac contraction to one or more templates.

25. The method of claim 24 , wherein the one or more templates comprise one or more of an intrinsic beat template, a fully-paced beat template, or a fusion beat template.

26. The method of claim 16 , wherein the value of at least one of the metrics indicates an amount of the contractions that were fusion beats.

27. The method of claim 26 , wherein the amount is a percentage of the contractions.

28. A system comprising:

means for receiving a mechanical motion signal from a sensor of the pacing device, the mechanical motion signal representative of mechanical activity motion of a heart;

for each of a plurality of cardiac cycles during which the pacing device delivered a ventricular pacing pulse for the CRT, means for identifying one or more features of a cardiac contraction within the mechanical motion signal during the cardiac cycle;

for each of the plurality of cardiac cycles, means for determining whether the cardiac contraction is a fusion beat based on the one or more features;

means for determining a value of at least one metric indicating the effectiveness of the CRT based on the determinations of whether the cardiac contractions are fusion beats; and

means for presenting the value of the at least one metric to a user via a user interface.

29. A computer-readable storage medium comprising instructions that, when executed by processing circuitry of a medical device system, cause the processing circuitry to:

receive a mechanical motion signal from a sensor of the pacing device, the mechanical motion signal representative of mechanical motion of a heart;

for each of a plurality of cardiac cycles during which the pacing device delivered a ventricular pacing pulse for the CRT, identify one or more features of a cardiac contraction within the mechanical motion signal during the cardiac cycle;

for each of the plurality of cardiac cycles, determine whether the cardiac contraction is a fusion beat based on the one or more features;

determine a value of at least one metric indicating the effectiveness of the CRT based on the determinations of whether the cardiac contractions are fusion beats; and

present the value of the at least one metric to a user via a user interface.

30. A system for determining the effectiveness of cardiac resynchronization therapy (CRT), the system comprising:

a pacing device configured to be implanted within a patient, the pacing device comprising:

a plurality of electrodes;

a signal generation circuitry configured to deliver ventricular pacing pulses for the cardiac resynchronization via the plurality of electrodes to a left ventricle;

a three-dimensional accelerometer configured to produce a mechanical motion signal representative of mechanical motion of the heart; and

a housing configured for implantation on or within the heart, wherein the signal generation circuitry and the sensor are within the housing;

processing circuitry configured to:

for each of a plurality of cardiac cycles during which the pacing device delivered one of the ventricular pacing pulses, identify one or more features of a cardiac contraction within the mechanical motion signal during the cardiac cycle;

for each of the plurality of cardiac cycles, determine whether the cardiac contraction is a fusion beat based on the one or more features; and

determine a value of at least one metric indicating the effectiveness of the CRT based on the determinations of whether the cardiac contractions are fusion beats; and

an external device configured to communicate with the pacing device, the external device comprising a user interface configured to present the value of the at least one metric to a user,

wherein the processing circuitry comprises processing circuitry of the external device and processing circuitry of pacing device, and wherein the one or more features of the cardiac contraction within the mechanical motion signal comprise an amount of motion in at least one direction other than the primary axis of motion during the cardiac contraction.