Systems and methods for managing heart rate dependent conditions
Systems and methods are provided for monitoring a cardiac condition of a patient. The system includes a sensor for receiving a patient's heart rate and a processor that is programmable to set a patient's safe heart rate zone. The processor is also configured to determine whether the patient's heart rate has exceeded the safe heart rate zone. In response to determining that the patient's heart rate has exceeded the safe heart rate zone, the processor may reprogram a new safe heart rate zone.
1. An implantable system for monitoring a cardiac condition of a patient, comprising:
a sensor for receiving a patient's heart rate and for monitoring at least one of T wave alternans and ST segment deviation; and
a processor coupled to the sensor, the processor being programmable to set a patient's safe heart rate zone, and the processor configured to:
identify a change in at least one of the monitored T wave alternans and the monitored ST segment deviation, and
in response to the identified change, reprogram the safe heart rate zone.
2. The system of claim 1 , wherein the system further comprises a transceiver, coupled to the processor, for sending an alert in response to the identified change, and for receiving information from a clinician.
3. The system of claim 2 , wherein the received information from the clinician includes information for readjusting the patient's safe heart rate zone, and wherein the processor is configured to adjust the safe heart rate zone based on the received information.
4. The system of claim 3 , further comprising surface electrocardiogram (ECG) electrodes for retesting a patient in response to the alert, the retesting comprising evaluating the overall cardiac condition of the patient.
5. The system of claim 4 , wherein the safe heart zone is reprogrammed if the retesting using the surface ECG electrodes confirms the occurrence of T wave alternans within the current safe heart rate zone.
6. The system of claim 4 , wherein the safe heart rate zone is reprogrammed if the retesting using the surface ECG electrodes confirms that the patient has ischemia.
7. The system of claim 1 , wherein the safe heart rate zone is defined by a patient's heart rate at above which the risk of adverse cardiac condition clinically increases.
8. The system of claim 1 , wherein the safe heart rate zone is defined by a patient's heart rate at above which abnormal changes to an electrocardiogram (ECG) occur.
9. The system of claim 8 , wherein the abnormal changes to the ECG include at least one of T wave alternans and ST segment depression.
10. The system of claim 1 , wherein the processor wirelessly transmits to a clinician the patient's heart rate when the heart rate exceeds the safe heart rate zone.
11. The system of claim 1 , wherein the processor alerts a clinician or patient when drift occurs in the safe heart rate zone.
12. The system of claim 1 , wherein the processor is configured to determine whether the patient's heart rate has exceeded the safe heart rate zone.
13. The system of claim 12 , wherein the system further comprises a memory for storing the duration of time that the patient's heart rate has exceeded the safe heart rate zone.
14. The system of claim 1 , wherein the processor automatically reprograms the safe heart rate zone if a T wave alternans is detected at a heart rate within the safe heart rate zone.
15. A method of managing a heart rate dependent medical condition comprising:
programming a processor of an implantable medical device with a patient's safe heart rate zone;
sensing a patient's heart rate with the implantable medical device;
monitoring, with the implantable medical device, at least one of T wave alternans and ST segment deviation;
identifying a change in at least one of the monitored T wave alternans and the monitored ST segment deviation; and
reprogramming the implantable medical device with a new safe heart rate zone in response to identifying the change.
16. The method of claim 15 , comprising comparing the patient's heart rate to the safe heart rate zone and transmitting to a remote terminal the result of the comparison between the patient's heart rate and the safe heart rate zone.
17. The method of claim 15 , comprising alerting a clinician when the patient's heart rate falls outside of the safe heart rate zone.
18. The method of claim 17 , comprising, in response to the alert, retesting the patient using a standard technique for evaluating the overall cardiac condition of the patient.
19. The method of claim 18 , wherein the standard technique is a test using surface ECG electrodes.
20. The method of claim 19 , comprising reprogramming the safe heart rate zone only when the surface ECG electrode test confirms that the patient has significant T wave alternans within the current safe heart rate zone.
21. The method of claim 17 , comprising modifying a medical therapy to maintain the patient's heart rate within the safe heart rate zone.
22. The method of claim 15 , wherein the heart rate dependent condition is risk of cardiac arrest.
23. The method of claim 22 , further comprising determining the increased risk of cardiac arrest by observing daily heart rate in excess of the onset heart rate for significant T wave alternans.
24. The method of claim 22 , wherein the risk of cardiac arrest is indicated by a decrease in the difference between the patient's daily heart rate and a maximum negative heart rate.
25. The method of claim 22 , wherein the risk of cardiac arrest is indicated by an overlap between daily heart rate and a maximum negative heart rate.
26. The method of claim 15 , wherein the heart rate dependent medical condition is cardiac ischemia.
27. The method of claim 26 , wherein an upper heart rate that defines the safe heart rate zone is determined by observing the heart rate at which clinical ischemia develops during stress testing.
28. The method of claim 26 , comprising modifying a medical therapy based on data received from the implantable medical device to maintain the patient's heart rate within the safe heart rate zone.
29. The method of claim 26 , further comprising determining increased amount of cardiac ischemia by observing increased heart rate adjusted T wave alternans.
30. The method of claim 26 , further comprising determining increased risk of cardiac ischemia by observing increased heart rate adjusted T wave alternans.
31. The method of claim 15 , wherein the heart rate dependent medical condition is heart failure.
32. The method of claim 31 , comprising determining potential progression of heart failure by observing increased heart rate adjusted T wave alternans.
33. The method of claim 32 , comprising alerting a clinician when the patient's heart rate falls outside the safe heart rate zone.
34. The method of claim 15 , further comprising determining a drift in the safe heart rate zone by observing changes in a surrogate marker measured by the implantable medical device.
35. The method of claim 34 , wherein the heart rate dependent condition is arrhythmias and the surrogate marker is implantable medical device measured T wave alternans.
36. The method of claim 34 , wherein the heart rate dependent condition is ischemia and the surrogate marker is implantable medical device measured ST segment deviation.
37. The method of claim 15 , comprising calculating a risk burden value of a patient by determining the proportion of time that the patient's heart rate is outside the safe heart rate zone and plotting the risk burden value against time.
38. The method of claim 15 , further comprising determining whether the patient's heart rate has exceeded the safe heart rate zone.
39. The method of claim 38 , further comprising storing, in a memory of the implantable medical device, the duration of time that the patient's heart rate has exceeded the safe heart rate zone.
40. The method of claim 15 , further comprising sending an alert in response to identifying the change.
41. The method of claim 15 , further comprising:
receiving, at the implantable medical device, information from a clinician that includes information for readjusting the safe heart rate zone; and
adjusting the safe heart rate zone based on the received information.
42. A computer-readable storage medium comprising instructions that cause a processor of an implantable medical device to:
store a patient's safe heart rate zone;
sense a patient's heart rate;
monitor at least one of T wave alternans and ST segment deviation;
identify a change in at least one of the monitored T wave alternans and the monitored ST segment deviation; and
reprogram a new safe heart rate zone in response to identifying the change.
43. The computer-readable storage medium of claim 42 , comprising instructions for alerting a clinician when the patient's heart rate falls outside of the safe heart rate zone.
44. The computer-readable storage medium of claim 42 , comprising instructions for reprogramming the safe heart rate zone only when a treadmill test confirms that the patient has significant T wave alternans within the current safe heart rate zone.
45. The computer-readable storage medium of claim 42 , comprising modifying a medical therapy to maintain the patient's heart rate within the safe heart rate zone.