ATRIAL-NATRIURETIC-FACTOR RELEASE DURING EXERCISE IN PATIENTS SUCCESSIVELY PACED IN DDD AND RATE MATCHED VENTRICULAR PACING

Dual chamber pacemakers were implanted in nine patients with permanent second or third degree AV block (eight had complete retrograde block). Two identical exercise tests were performed after at least 1 month after implantation. During the first test (T1) the pacemaker was programmed to the DDD mode and heart rates were recorded every 15 to 30 seconds during exercise and 30 minutes after exercise. Following 30 minutes of rest, the implanted pacemaker was programmed to the VVT mode and driven by an external pacemaker via a skin electrode. The second exercise test (T2) was then performed and the rate of the external pacemaker was progressively changed to reproduce exactly the rate observed during T1 at the same exercise stress. Atrial natriuretic factor (ANF) levels were determined at rest, at regular intervals during exercise, and 30 minutes after exercise. ANF levels and release were statistically higher during rate matched ventricular, than DDD pacing. It is concluded that preservation of AV synchrony reduces ANF release induced by heart rate acceleration during exercise.