EVALUATION OF ACUTE DUAL-CHAMBER PACING WITH A RANGE OF ATRIOVENTRICULAR DELAYS ON CARDIAC-PERFORMANCE IN REFRACTORY HEART-FAILURE

Objectives. This study evaluated how variations in atrioventricular (A V) delay affect hemodynamic function in patients with refractory heart failure being supported with intravenous inotropic and intravenous or oral inodilating agents. Background. Although preliminary data have s uggested that dual chamber pacing with short AV delays may improve car diac function in patients,vith heart failure, detailed Doppler and inv asive hemodynamic assessment of patients,vith refractory New York Hear t Association class IV heart failure has not been performed. Methods. Nine patients with functional class IV clinical heart failure had Dopp ler assessment of transvalvular how and right heart catheterization pe rformed during pacing at AV delays of 200, 150, 100 and 50 to 75 ms. R esults. Systemic arterial, pulmonary artery, right atrial and pulmonar y capillary wedge pressures, cardiac index, systemic and pulmonary vas cular resistances, stroke volume index, left ventricular stroke work i ndex (SWI) and arteriovenous oxygen content difference demonstrated no significant changes during dual-chamber pacing with AV delays of 200 to 50 to 75 ms. There were also no changes in the Doppler echocardiogr aphic indexes of systolic or diastolic ventricular function. The study was designed with SWI as the outcome variable. Assuming a clinically significant change in the SWI of 5 g/min per m(2), a type I error of 0 .05 and the observed standard deviation from our study, the observed p ower of our study is 85% (type II error of 15%). Conclusions. Changes in AV delay between 200 and 50 ms during dual-chamber pacing do not si gnificantly affect acute central hemodynamic data, including cardiac o utput and systolic or diastolic ventricular function in patients with severe refractory heart failure due to dilated cardiomyopathy. (C) 199 7 by the American College of Cardiology.