Optimization of the atrioventricular interval during rest and exercise in DDR-pacing

Several studies have been performed to evaluate the hemodynamic benefits of the optimal atrioventricular (AV) interval in DDD-pacing. The different effective intrinsic conduction (PR) intervals during atrial pacing as opposed to atrial sensing have been shown. The delay from the atrial stimulus to the onset of atrial depolarization (AP-delay) depends on the type of atrial disease and the site of stimulation. Most DDD and DDDR-pacemakers have therefore a corrected AV-interval afeter atrial pacing ansensing. This AV-correction is fixed or in some pacers programmable, in addition you may program a rate response AV-delay, that means a shortening AV-interval with an increasing pacing rate in order to simlate the physiologic and exercise. The AP-dealys were evaluated in 34 patients with sick sinus syndrome and chronotropic incopetence during rest and bicycle ergometer stress test at 25,50,75 and 100 watts (W). The AP-delay was defined as the difference between PR and atrial stimulated conduction (AR). nall patients a Synchrony DDR pacemaker (Pacesetter) had been implanted. A standard lead ECG and intracardiac PR + AR-interval was recorded during rest and exercise. The intracardiac signals weretransmitted via the implanted pacemaker. In 5 patients an esophagela lead was additionally recordded. In 34 patients during rest the mean PR-interrval was 186.9 ms, range 135-250 ms, the AR-interval was 263.8 ms, range 197-340 ms and the AP-delay 76.5 ms, range 45-134 ms. The mean AP-delay during exercise with alod of 25 W was 56.7 ms (n=24), at 50 w 45.4 ms (n=21), at 75w 22.1 (n=13) and at 100w 26.0 ms (n=7). In conclusion: the AP-delay vares from patient to patient, therefore a fixed AV-cirrection is not useful. The shortening of the AP-delay during exercise depends on the presence of catecholamines and the individual work load. An optimized AV-interval during rest and exercise, should be automatically adjusted to the AP-delay. (AU)