Morphology-based optimization of cardiac resynchronization therapy
A method and apparatus for delivering cardiac resynchronization therapy (CRT) in which an evoked response electrogram is recorded during one or more cardiac cycles and used to aid in the selection of resynchronization pacing parameters and/or to monitor the effectiveness of resynchronization therapy. The morphology of an evoked response electrogram may be recorded and analyzed to determine if and when intrinsic activation of one ventricle is occurring in order to optimally adjust the programmed atrio-ventricular (AV) delay interval for ventricular resynchronization pacing of a patient with intact AV node conduction.
1. A method for operating a cardiac rhythm management device in a patient, comprising:
delivering paces to both right and left ventricles in accordance with a programmed biventricular pacing mode, such that the paces are delivered at a programmed biventricular offset interval and after a programmed AV delay interval with respect to an atrial event;
switching to a single ventricle pacing mode and recording an evoked response test electrogram during a single ventricle pace with the programmed AV delay interval;
comparing the test electrogram to an evoked response template electrogram previously recorded during single ventricle pacing when the programmed AV delay interval was known to be matched to the patient's then existing intrinsic AV interval;
adjusting the programmed AV delay interval to match the patient's current intrinsic AV interval based upon the comparison of the test and template electrograms;
returning to the biventricular pacing mode with the adjusted AV delay interval.
2. The method of claim 1 wherein the comparing of the test and template electrograms further comprises:
determining when peaks in the test and template electrograms occur relative to the pace;
shortening the programmed AV delay interval if the peak in the test electrogram occurs earlier than the peak in the template; and,
lengthening the programmed AV delay interval if the peak in the test electrogram occurs later than the peak in the template.
3. The method of claim 1 further comprising determining matched programmed AV delay intervals at a plurality of different pacing rates.
4. The method of claim 3 further comprising:
using the matched AV delay intervals as determined at the plurality of pacing rates may to form a mapping function which maps particular pacing rates to particular programmed AV delay intervals; and,
automatically adjusting the programmed AV delay interval according to the mapping function as the pacing rate changes.
5. A cardiac rhythm management device, comprising:
pacing channels through which paces may be delivered to both right and left ventricles;
one or more sensing channels;
a controller programmed to deliver the paces in accordance with a programmed biventricular pacing mode at a programmed biventricular offset interval and after a programmed AV delay interval with respect to an atrial event;
wherein the controller is programmed to:
switch to a single ventricle pacing mode and recording an evoked response test electrogram during a single ventricle pace with the programmed AV delay interval;
compare the test electrogram to an evoked response template electrogram previously recorded during single ventricle pacing when the programmed AV delay interval was known to be matched to the patient's then existing intrinsic AV interval;
adjust the programmed AV delay interval to match the patient's current intrinsic AV interval based upon the comparison of the test and template electrograms;
return to the biventricular pacing mode with the adjusted AV delay interval.
6. The device of claim 5 wherein the controller is further programmed to compare the test and template electrograms and adjust the programmed AV delay interval by:
determining when peaks in the test and template electrograms occur relative to the pace;
shortening the programmed AV delay interval if the peak in the test electrogram occurs earlier than the peak in the template; and,
lengthening the programmed AV delay interval if the peak in the test electrogram occurs later than the peak in the template.
7. The device of claim 5 wherein the controller is further programmed to determine matched programmed AV delay intervals at a plurality of different pacing rates.
8. The device of claim 7 wherein the controller is further programmed to:
use the matched AV delay intervals as determined at the plurality of pacing rates may to form a mapping function which maps particular pacing rates to particular programmed AV delay intervals; and,
automatically adjust the programmed AV delay interval according to the mapping function as the pacing rate changes.