Cardiac resynchronization was effective for moderate-to-severe heart failure with intraventricular conduction delay.

P a t i e n t s 453 patients (mean age 64 y, 68% men) who had moderate or severe (New York Heart Association [NYHA] functional class III or IV) chronic heart failure resulting from ischemic or nonischemic cardiomyopathy; received stabilized doses of medication for ≥ 1 month (≥ 3 mo for β-blockers); and had left ventricular ejection fraction ≤ 35%, a QRS interval ≥ 130 msec, and a 6-minute walking distance ≤ 450 m. Exclusion criteria included use of pacemakers or cardioverterdefibrillators, a cardiac or cerebral ischemic event in the previous 3 months, and atrial arrhythmia in the previous month. Followup was ≥ 90% for all outcomes. I n t e r v e n t i o n All patients received implantation of a cardiac-resynchronization device (InSync model 8040, Medtronic, Minneapolis, MN, USA) with 3 pacing leads: a standard right atrial lead, a standard right ventricular lead, and a specialized left ventricular lead. Patients were allocated to atrial-synchronized biventricular pacing (n = 228) or no pacing (n = 225).