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Atrial-Based vs. Ventricular Pacing: A Meta-Analysis

Atrial-based pacing reduced the incidence of atrial fibrillation and, to a lesser extent, stroke.

Among the most important advances in pacemaker technology is atrial-based (dual-chamber) pacing, which helps to maintain atrioventricular synchrony. In addition to improving cardiac output, atrial-based pacing has been shown to limit the incidence of atrial fibrillation (AF); see the CTOPP trial (Journal Watch Cardiology Jul 14 2000) and the MOST trial (Journal Watch Cardiology Jul 26 2002). No individual trial has shown that atrial-based pacing substantially reduces risks for death or stroke, so these researchers conducted a meta-analysis of eight randomized trials of atrial-based versus ventricular pacing published since 1994. The trials involved about 8000 patients (52% with sinus-node dysfunction).

Compared with ventricular pacing, atrial-based pacing showed no significant reductions in risks for all-cause mortality, heart-failure hospitalization, or stroke and cardiovascular mortality combined. However, atrial-based pacing was associated with significantly reduced risk for incident AF (hazard ratio, 0.80; 95% CI, 0.72–0.89) and a borderline-significant reduction in risk for stroke (HR, 0.81; 95% CI, 0.67–0.99). No particular subgroup, including patients with sinus-node dysfunction, appeared to derive special overall benefit from atrial-based pacing. Furthermore, the implant complication rate was nearly twice as high with atrial-based than with ventricular pacing (6.2% vs. 3.2% among patients who received devices with dual-chamber capability). Most of the excess complications were due to lead dislodgements and infections.

Comment: This meta-analysis reaffirms findings from individual trials of atrial-based versus ventricular pacing. Reduced incidence of atrial fibrillation was the only clear benefit of atrial-based pacing, which was associated with more implant complications than was ventricular pacing. The authors caution that because some of the trials included patients with atrioventricular block, who may be less likely to benefit from atrial-based pacing, its overall value in patients with sinus-node dysfunction could have been underestimated. They also note that new dual-chamber pacing modes that minimize right-ventricular pacing have been developed and that their potential benefits in sick-sinus syndrome could surface in forthcoming trials. An accompanying editorial notes that most patients likely will continue to receive atrial-based pacing because of its benefits in preventing AF and, to a lesser extent, stroke, as well as perceived benefits in exercise capacity and quality of life. The editorialists also identify areas for future research, such as defining the role of pacemaker diagnostics and monitor function for guiding therapy in patients at high risk for AF and stroke.

— Mark D. Carlson, MD

Published in Journal Watch Cardiology July 26, 2006

Citation(s):

Healey JS et al. Cardiovascular outcomes with atrial-based pacing compared with ventricular pacing: Meta-analysis of randomized trials, using individual patient data. Circulation 2006 Jul 4; 114:11-7.

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• Medline abstract (Free)

Tse H-F and Lau C-P. Clinical trials for cardiac pacing in bradycardia: The end or the beginning? Circulation 2006 Jul 4; 114:3-5.

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• Medline abstract (Free)