[The influence of A-V synchrony and changes in heart rate on rate responsive pacing]

To evaluate the hemodynamics during physiological cardiac pacing, influence of A-V synchrony, changes in heart rate and physical exercise on cardiac function were studied. In observing the effects of increasing heart rate in acute cases, C1, mAp, PaWP, and CVP show a clear improvement with physiological pacing (AAI or DVI). However, SSS cases with VVI pacemakers show a clear decline in cardiac function with increased heart rate. EF and ER, which indicate ventricular contractility, showed improvement with physical exercise and increased heart rate under physiological pacing, but actually decreased under VVI pacing. PFR, which indicate diastolic function, showed an identical tendency. Thus, it was concluded that: 1. The most important factor affecting cardiac function during pacing is A-V synchrony, followed by increased heart rate and physical exercise. 2. VVI pacing at high pacing rates showed an adverse influence on cardiac function. This was mostly observed in VVI pacing for SSS cases. 3. Thus, we may recommend AAIR pacing for SSS with normal A-V conduction, and DDD pacing for SSS cases with abnormal A-V conduction on CAVB without Af.