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Background:
Observational studies suggest that conventional right ventricular apical pacing may have a deleterious effect on left ventricular function. In this study, we examined whether biventricular pacing is superior to right ventricular apical pacing in preventing deterioration of left ventricular systolic function and cardiac remodeling in patients with bradycardia and a normal ejection fraction.
Methods:
In this prospective, double-blind, multicenter study, we randomly assigned 177 patients in whom a biventricular pacemaker had been successfully implanted to receive biventricular pacing (89 patients) or right ventricular apical pacing (88 patients). The primary end points were the left ventricular ejection fraction and left ventricular end-systolic volume at 12 months.
Results:
At 12 months, the mean left ventricular ejection fraction was significantly lower in the right-ventricular-pacing group than in the biventricular-pacing group (54.8±9.1% vs. 62.2±7.0%, P<0.001), with an absolute difference of 7.4 percentage points, whereas the left ventricular end-systolic volume was significantly higher in the rightventricular-pacing group than in the biventricular-pacing group (35.7±16.3ml vs. 27.6±10.4ml, P<0.001), with a relative difference between the groups in the change from baseline of 25% (P<0.001). The deleterious effect of right ventricular apical pacing occurred in prespecified subgroups, including patients with and patients without preexisting left ventricular diastolic dysfunction. Eight patients in the right-ventricular-pacing group (9%) and one in the biventricular-pacing group (1%) had ejection fractions of less than 45% (P=0.02). There was one death in the right-ventricular-pacing group, and six patients in the right-ventricular-pacing group and five in the biventricular-pacing group were hospitalized for heart failure (P=0.74).
Conclusions:
In patients with normal systolic function, conventional right ventricular apical pacing resulted in adverse left ventricular remodeling and in a reduction in the left ventricular ejection fraction; these effects were prevented by biventricular pacing. (Centre for Clinical Trials number, CUHK_CCT00037.)
Figure 2: Comparison of primary end points at 12 months between patients who received biventricular pacing and those who received right ventricular apical pacing. The values shown are means. Among patients who received right ventricular apical (RVA) pacing, there was a significant decrease in the left ventricular ejection fraction (Panel A), whereas the left ventricular endsystolic volume was increased (Panel B). I bars indicate 95% confidence intervals. BiV denotes biventricular, and LV left ventricular. (Reprinted from Yu C-M, Chan JY-S, Zhang Q, et al. Biventricular pacing in patients with bradycardia and normal ejection fraction. N Engl J Med. 2009;361:2123-2134. Copyright 2009 Massachusetts Medical Society. All rights reserved.)
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