Apparatus and method for ventricular rate regularization

Abstract

A method and system for operating a cardiac rhythm management device which employs pacing therapy to regularize the ventricular rhythm. Such ventricular rate regularization may be employed with conventional bradycardia pacing, ventricular resynchronization therapy, or anti-tachyarrhythmia therapy.

What is claimed is:  
     
         1 . A method for operating a cardiac pacemaker, comprising: 
 sensing ventricular depolarizations through a ventricular sensing channel and generating ventricular sense signals in accordance therewith;    pacing a ventricle upon expiration of a ventricular escape interval without receiving a ventricular sense from the ventricular sensing channel, wherein the ventricular escape interval starts with either a ventricular pace or a ventricular sense, the reciprocal of the ventricular escape interval being the lower rate limit of the pacemaker;    measuring an R-R interval associated with each ventricular sense, wherein an R-R interval is the time between a ventricular sense and the preceding ventricular sense or ventricular pace, the reciprocal of the R-R interval thus being the measured intrinsic ventricular rate; and,    adjusting the ventricular escape interval in accordance with a measured R-R interval so that the lower rate limit adjusts in accordance with changes in the measured intrinsic ventricular rate.    
     
     
         2 . The method of  claim 1  wherein the ventricular escape interval is adjusted to move toward the measured R-R interval multiplied by a scaling factor.  
     
     
         3 . The method of  claim 2  wherein the ventricular escape interval is adjusted by computing a weighted average of the measured R-R interval multiplied by a scaling factor and the value of the ventricular escape interval.  
     
     
         4 . The method of  claim 1  wherein the ventricular escape interval is adjusted in accordance with a measured R-R interval after each ventricular sense.  
     
     
         5 . The method of  claim 1  further comprising adjusting the ventricular escape interval toward a value corresponding to a base lower rate limit after a ventricular pace.  
     
     
         6 . The method of  claim 5  wherein the ventricular escape interval is adjusted after a ventricular pace by multiplying the escape interval by a decay coefficient.  
     
     
         7 . The method of  claim 1  wherein the ventricular escape interval is adjusted by computing a weighted average of the measured R-R interval multiplied by a scaling factor and the previous value of the ventricular escape interval after each ventricular sense, and wherein the ventricular escape interval is adjusted by multiplying the escape interval by a decay coefficient after a ventricular pace.  
     
     
         8 . The method of  claim 7  wherein the scaling factor is selected to be greater than one such that the lower rate limit of the pacemaker is moved toward a fraction of the intrinsic ventricular rate after each ventricular sense.  
     
     
         9 . The method of  claim 7  wherein the scaling factor is selected to be less than one such that the lower rate limit of the pacemaker is moved toward a value that is above the intrinsic ventricular rate after each ventricular sense.  
     
     
         10 . The method of  claim 1  further comprising: 
 sensing ventricular rate and synchronized heart chambers through separate channels and generating sense signals upon detection of depolarization occurring in a chamber;  
 pacing the rate ventricle upon expiration of a ventricular escape interval without receiving a ventricular sense from the rate ventricular sensing channel, wherein the ventricular escape interval starts with either a ventricular pace or a ventricular sense, the reciprocal of the ventricular escape interval being the lower rate limit of the pacemaker;  
 measuring an R-R interval associated with each ventricular rate chamber sense, wherein an R-R interval is the time between a ventricular sense and the preceding ventricular sense or ventricular pace, the reciprocal of the R-R interval thus being the measured intrinsic ventricular rate;  
 adjusting the ventricular escape interval in accordance with the measured R-R interval so that the lower rate limit adjusts in accordance with changes in the measured intrinsic ventricular rate; and,  
 pacing the synchronized ventricle in accordance with a synchronized pacing mode wherein a synchronized ventricle pace is delivered at a specified pacing instant defined with respect to expiration of a rate ventricle escape interval.  
 
     
     
         11 . A cardiac rhythm management device, comprising: 
 a ventricular sensing channel for sensing ventricular depolarizations and generating ventricular sense signals in accordance therewith;    a ventricular pacing channel for pacing a ventricle;    a controller for controlling operation of the device such that a ventricular pace is delivered upon expiration of a ventricular escape interval without receiving a ventricular sense from either ventricular sensing channel, wherein the ventricular escape interval starts with either a ventricular pace or a ventricular sense, the reciprocal of the ventricular escape interval being the lower rate limit of the pacemaker;    wherein the controller is configured to measure an R-R interval associated with each ventricular sense, wherein an R-R interval is the time between a ventricular sense and the preceding ventricular sense or ventricular pace, the reciprocal of the R-R interval thus being the measured intrinsic ventricular rate; and,    wherein the controller is configured to be capable of adjusting the ventricular escape interval in accordance with a measured R-R interval so that the lower rate limit adjusts in accordance with changes in the measured intrinsic ventricular rate.    
     
     
         12 . The device of  claim 11  wherein the ventricular escape interval is adjusted to move toward the measured R-R interval multiplied by a scaling factor.  
     
     
         13 . The device of  claim 12  wherein the ventricular escape interval is adjusted by computing a weighted average of the measured R-R interval multiplied by a scaling factor and the previous value of the ventricular escape interval.  
     
     
         14 . The device of  claim 11  wherein the ventricular escape interval is adjusted in accordance with a measured R-R interval after each ventricular sense.  
     
     
         15 . The device of  claim 11  wherein the controller is configured to adjust the ventricular escape interval toward a value corresponding to a base lower rate limit after a ventricular pace.  
     
     
         16 . The device of  claim 11  wherein the controller is configured to adjust the ventricular escape interval after a ventricular pace by multiplying the escape interval by a decay coefficient.  
     
     
         17 . The device of  claim 11  wherein the controller is configured to adjust the ventricular escape interval by computing a weighted average of the measured R-R interval multiplied by a scaling factor and the previous value of the ventricular escape interval after each ventricular sense, and wherein the ventricular escape interval is adjusted by multiplying the escape interval by a decay coefficient after a ventricular pace.  
     
     
         18 . The device of  claim 12  wherein the scaling factor is selected to be greater than one such that the lower rate limit of the device is moved toward a fraction of the intrinsic ventricular rate after each ventricular sense.  
     
     
         19 . The device of  claim 12  wherein the scaling factor is selected to be less than one such that the lower rate limit of the device is moved toward a value that is above the intrinsic ventricular rate after each ventricular sense.  
     
     
         20 . The device of  claim 11  further comprising: 
 sensing channels for sensing depolarizations from ventricles designated as a rate ventricle and a synchronized ventricle;  
 wherein the ventricular escape interval and R-R intervals are defined with respect to rate ventricle events; and,  
 wherein the controller is programmed to pace the synchronized chamber in accordance with a synchronized pacing mode such that a synchronized ventricle pace is delivered at a specified pacing instant defined with respect to expiration of the rate ventricle escape interval.  
 
     
     
         21 . The device of  claim 11  further comprising a shock pulse generator and shock electrodes for delivering a defibrillation shock to a heart chamber upon detection of a tachyarrhythmia.  
     
     
         22 . The device of  claim 21  wherein the device is configured to deliver defibrillation shocks to the atria.  
     
     
         23 . The device of  claim 21  wherein the controller is programmed such that the ventricular escape interval is adjusted in accordance with a measured R-R interval upon detection of a tachyarrhythmia.