SYSTOLIC AND DIASTOLIC EFFECTS OF VARIABLE ATRIOVENTRICULAR DELAY IN PATIENTS WITH COMPLETE HEART-BLOCK AND NORMAL VENTRICULAR-FUNCTION

This study wets designed to demonstrate the effects of varying the atr ioventricular delay (AVD) on ventricular diastolic filling dynamics an d the resultant stroke volume in patients with complete heart block an d normal cardiac function. We studied 7 patients with normal cardiac f unction in whom a dual chamber pacemaker had been implanted because of complete heart block. Doppler and M-mode echocardiography was perform ed at 70, 100, 140, 180, and 220 ms, AVD with the device in DDD mode a t a rate of 80 beats/min. The effects of these variable intervals on t he contribution of the E and A waveform to the diastolic filling, on t he stroke volume, and on the systolic intervals were evaluated. Optimi zation of this interval, with a 19% increase in stroke volume was achi eved in the group of patients at an AVD of 140 ms. When considered ind ividually, the AVD associated with the largest stroke volume, was 100 ms in 2 patients and 140 ms in the remaining 5. At this individual opt imal AVD the ventricular septal contraction occurred 31 +/- 14 ms, bef ore the end of the transmitral flow. The optimal AVD is, therefore, th e one which synchronizes the ventricular and atrial systole so that th e first ventricular septal contraction occurs after the peak of the A wave, just before the end of the transmitral flow. Because of the diff erent functional cardiovascular status of the single patient, this par ameter should be individualized; this can be clinically important as i t may lead, in this patient population, to an improvement of the strok e volume up to 42%. (C) 1997 by Excerpta Medica, Inc.