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Baseline and long-term follow-up 2-dimensional echocardiograms were obtained in 160 patients with automatic implantable cardioverter-defibrillators without indications for antibradycardia pacing, who had backup ventricular pacing at a rate of 40/minute (VVI-40) or dual-chamber rate-responsive pacing at a rate of 70/minute (DDDR-70). At 37 months of follow-up for 80 patients treated with VVI-40 and 23 months of follow-up for 80 patients treated with DDDR-70, the mean left ventricular ejection fraction was 36 ± 8% at baseline and 36 ± 8% at follow-up and 36 ± 7% at baseline and 30 ± 7% at follow-up (p <0.01), respectively. At follow-up, the left ventricular ejection fraction was decreased >7% in 25 of 80 patients (31%)treated with DDDR-70 and in 9 of 80 patients (11%) treated with VVI-40 (p <0.01). A new left ventricular wall motion abnormality developed in 23 of 80 patients (29%) treated with DDDR-70 and in 11 of 80 patients (14%) treated with VVI-40 (p <0.025). [Copyright &y& Elsevier]