IMPORTANCE OF HEART-RATE RESPONSE DURING EXERCISE IN PATIENTS USING ATRIOVENTRICULAR SYNCHRONOUS AND VENTRICULAR PACEMAKERS

Atrioventricular synchronous pacing offers advantages over fixed‐rate ventricular (VVI) pacing both at rest and during exercise. This study compared the hemodynamic effects at rest and exercise of ventricular pacing at a rate of 70 beats/mm, ventricular pacing where the rate was increased during exercise and duaJ chamber pacing. Ten patients, age 63.8 years, with multiprogrammable DDD pacemakers were studied using supine bicycle radionuclide ventriculography. RadionucJide data during dual chamber pacing was acquired at rest and during a submaximal workload of 200‐400 kpm/min. The pacemakers were then programmed to VVI pacing at a rate of 70 beats/min, and 1 week later, studies were repeated in the VVI mode at rest, during exercise at a rate of 70 beats/min, and during exercise with the WI pacemaker programmed to a rate adapted to the ODD pacing exercise rate. At rest, (he cardiac output was lower in the WI compared with the AV sequential mode (4.1 ±1.1 vs 5.7±1.1 1/mm, P < 0.01). During exercise, the cardiac output increased from resting values in the DDD and WI pacing modes, however cardiac output in the rate‐adapted WI mode was higher than in the WI mode with the rate maintained at 70 beats/min (8.1 ±1.5 vs 6.3 ±1.1 1/min, P = 0.02). Three patients completed lower workloads with WI pacing at 70 beats/min compared with AV synchronous pacing. At rest, AV sequential pacing was superior to WI pacing, suggesting the importance of the atrial contribution to ventricular filling. With WI pacing during exercise, cardiac output was improved with an increased pacemaker rate, suggesting that the heart rate response during exercise was the major determinant of the higher cardiac output. Copyright © 1990, Wiley Blackwell. All rights reserved