The importance of different atrioventricular intervals for exercise capacity.

In order to determine whether different atrioventricular intervals influence the maximal exercise capacity, 15 patients with second degree or complete atrioventricular block and no signs of left ventricular failure were studied. They all had atrioventricular synchronous pacemakers. Maximal exercise tests (sitting bicycle ergometry) were performed at four different atrioventricular intervals (50, 100, 150, and 200 ms) and during rate-matched asynchronous ventricular pacing. The patients thereby served as their own controls. Ventricular rate, maximal oxygen uptake and minute ventilation were measured and perceived exertion estimated every minute. Different atrioventricular intervals did not affect the maximal exercise capacity, the maximal oxygen uptake, the perceived exertion or minute ventilation. Since the results were similar during atrioventricular synchronous pacing at various atrioventricular intervals and on rate-matched asynchronous ventricular pacing, this study supports previous findings that the important factor for maximal physical performance is not a preserved atrioventricular synchronization but the ability to increase the ventricular rate.