LCP based predictive timing for cardiac resynchronization
Methods, systems and devices for providing cardiac resynchronization therapy (CRT) to a patient using a leadless cardiac pacemaker (LCP) implanted in or proximate the left ventricle of a patient. A setup phase is used to establish parameters in the therapy delivery. In operation, the method and/or device will sense at least one non-paced cardiac cycle to determine a native R-R interval, and then delivers a synchronization pace at an interval less than the native R-R interval followed by a plurality of pace therapies delivered at the R-R interval or a modification thereof.
1. A leadless cardiac pacemaker (LCP) configured for implantation entirely within a heart chamber of a patient or adjacent to a heart chamber of a patient, the LCP comprising:
a plurality of electrodes for cardiac therapy delivery and cardiac electrical sensing;
pacing circuitry configured to generate pacing therapy outputs; and
control circuitry configured to analyze signals from the electrodes and to control the use of the pacing circuitry for cardiac resynchronization therapy (CRT);
wherein the control circuitry is configured for:
sensing a native R-R interval from the patient's heart;
calculating a synchronization interval by reducing the native R-R interval using a reduction factor;
sensing a native ventricular event;
delivering a synchronization pace therapy upon expiration of the synchronization interval following the native ventricular event; and
delivering a predetermined number, N, of additional pace therapies at intervals approximately equal to the native R-R interval.
2. The LCP of claim 1 , wherein the control circuitry is configured to provide the CRT without using an atrial sense reference.
3. The LCP of claim 1 , wherein the control circuitry is configured to perform an initialization of CRT to determine the reduction factor by:
determining a PR interval for the patient's cardiac activity; and
multiplying the PR interval by a variable, % PR, to calculate the reduction factor.
4. The LCP of claim 1 , wherein the control circuitry is configured to perform an initialization of CRT to determine the reduction factor by:
sensing one or more native ventricular events to calculate an RR interval between native ventricular events and a PR interval within one or more native ventricular events;
calculating a RR:PR ratio as a ratio of the RR interval to the PR interval;
obtaining a variable, % PR, from memory or from an external programmer; and
calculating the reduction factor as one minus the product of the first variable and the % PR; and
further wherein the control circuitry is configured to calculate the synchronization interval by multiplying the reduction factor and the native beat interval.
5. The LCP of claim 1 , wherein the control circuitry is configured to perform an initialization of CRT to determine the reduction factor by:
sensing one or more native ventricular events to calculate an RR interval between native ventricular events;
communicating with a second device to determine when P-waves occurred in the one or more native ventricular events and calculating a PR interval;
calculating a RR:PR ratio as a ratio of the RR interval to the PR interval;
obtaining a variable, % PR, from memory or from an external programmer; and
calculating the reduction factor as one minus the product of the first variable and the % PR; and
further wherein the control circuitry is configured to calculate the synchronization interval by multiplying the reduction factor and the native beat interval.
6. The LCP of claim 1 , wherein the control circuitry is configured to monitor patient status and make adjustments to the CRT including:
sensing for a patient condition that would influence the reduction factor;
detecting a change in the patient condition; and
adjusting the reduction factor.
7. The LCP of claim 1 , further comprising a posture sensor, wherein the control circuitry is configured to monitor patient posture and make adjustments to the CRT including:
sensing a posture of the patient;
determining whether the patient has changed postures; and
in response to finding that the patient has changed postures, adjusting the reduction factor.
8. The LCP of claim 1 , wherein the control circuitry is configured to monitor patient status and make adjustments to the CRT including sensing for a predetermined patient condition that may influence PR interval, and in response to sensing the predetermined patient condition, adjusting “N”.
9. The LCP of claim 1 , further comprising a posture sensor, wherein the control circuitry is configured to monitor patient posture and make adjustments to the CRT including:
sensing a posture of the patient;
determining that the patient has changed postures between standing and one of sitting or laying down; and:
if the patient has gone from standing to sitting or laying down, increasing “N”; or
if the patient has gone from sitting or laying down to standing, reducing “N”.
10. The LCP of claim 1 , wherein the control circuitry is configured to iteratively provide the CRT in sets and to adjust N after delivery of a plurality of sets by:
observing changes in native R-R intervals, to calculate an R-R drift; and
calculating N using the calculated drift.
11. The LCP of claim 1 , wherein the control circuitry is configured for at least first and second modes of CRT therapy wherein:
the first mode comprises delivering sets of CRT therapy via the combination of sensing a native R-R interval, delivering a synchronization pace therapy, and delivering a plurality of additional pace therapies;
the second mode comprises obtaining atrial event timing information from a second implantable or wearable medical device to control or optimize pace therapy timing.