Effects of multisite biventricular pacing in patients with heart failure and intraventricular conduction delay.

Background: One third of patients with chronic heart failure have electroca rdiographic evidence of a major intraventricular conduction delay, which ma y worsen left ventricular systolic dysfunction through asynchronous ventric ular contraction. Uncontrolled studies suggest that multisite biventricular pacing improves hemodynamics and well-being by reducing ventricular asynch rony. We assessed the clinical efficacy and safety of this new therapy. Methods: Sixty-seven patients with severe heart failure (New York Heart Ass ociation class III) due to chronic left ventricular systolic dysfunction, w ith normal sinus rhythm and a duration of the QRS interval of more than 150 msec, received transvenous atriobiventricular pacemakers (with leads in on e atrium and each ventricle). This single-blind, randomized, controlled cro ssover study compared the responses of the patients during two periods: a t hree-month period of inactive pacing (ventricular inhibited pacing at a bas ic rate of 40 bpm) and a three-month period of active (atriobiventricular) pacing. The primary end point was the distance walked in six minutes; the s econdary end points were the quality of life as measured by questionnaire, peak oxygen consumption, hospitalizations related to heart failure, the pat ients' treatment preference (active vs. inactive pacing), and the mortality rate. Results: Nine patients were withdrawn from the study before randomization, and 10 failed to complete both study periods. Thus, 48 patients completed b oth phases of the study. The mean (+/-SD) distance walked in six minutes wa s 23 percent greater with active pacing (399+/-100 m vs. 326+/-134 m, P<0.0 01), the quality-of-life score improved by 32 percent (P<0.001), peak oxyge n uptake increased by 8 percent (P<0.03), hospitalizations were decreased b y two thirds (P<0.05), and active pacing was preferred by 85 percent of the patients (P<0.001). Conclusions: Although it is technically complex, atriobiventricular pacing significantly improves exercise tolerance and quality of life in patients w ith chronic heart failure and intraventricular conduction delay. (N Engl J Med 2001;344:873-80.) Copyright (C) 2001 Massachusetts Medical Society.