Dual chamber versus single chamber ventricular pacemakers for sick sinus syndrome and atrioventricular block

Abstract

Background: “Physiologic” pacing, either dual chamber or single chamber atrial pacing, is believed to have an advantage over single chamber ventricular pacing. It is thought to resemble cardiac physiology more closely by maintaining atrioventricular (AV) synchrony and dominance of the sinus node and may reduce cardiovascular morbidity and mortality. At the time of the initial publication of this review in 2004, there was no clear preference and a significant proportion of implanted devices were single chamber pacemakers. Since the original review, important additional trials have been published and an update to this review is necessary. Objectives: The objective of this review was to assess the short- and long-term clinical effectiveness of dual chamber pacemakers compared to single chamber ventricular pacemakers in adults with AV block, sick sinus syndrome or both. An additional objective was to assess separately any potential differences in effectiveness between dual chamber pacing and single chamber atrial pacing. The clinical effectiveness of single chamber atrial pacing versus single chamber ventricular pacing was not examined. Search methods: To avoid duplication of effort, we checked reference lists of previous systematic reviews. The searches conducted in 2002 were updated in July 2015. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2022, Issue 4), MEDLINE OVID and EMBASE OVID. There were no language restrictions. Selection criteria: Parallel group or crossover randomised controlled trials of at least 48 hours duration comparing dual chamber pacing and single chamber ventricular pacing, and investigating cardiovascular morbidity, mortality, patient related quality of life, exercise capacity and complication rates. Data collection and analysis: Two review authors independently selected for inclusion and extracted data. Data was extracted onto pre-piloted data extraction forms. Where appropriate data was available, meta-analysis was performed. Where meta-analysis was not possible, the number of studies showing a positive, neutral or negative direction of effect and statistical significance were simply counted. Main results: The latest search found four new studies and updated follow-up data on one study. Seven parallel and 28 crossover randomised controlled trials were identified. The quality of reporting was found to be poor. Pooled data from parallel studies shows a statistically non-significant preference for physiologic pacing (primarily dual chamber pacing) for the prevention of heart failure and mortality, and a statistically significant beneficial effect regarding the prevention of atrial fibrillation (odds ratio (OR) 0.81, 95% CI 0.71 to 0.93) and prevention of stroke (OR 0.77, 95% Ci 0.60 to 0.99). Both parallel and crossover studies favour dual chamber pacing with regard to pacemaker syndrome (parallel: Peto OR 0.11, 95% CI 0.08 to 0.14; crossover: standardised mean difference (SMD) -0.74, 95% CI - 0.95 to -0.52). Pooled data from crossover studies shows a statistically significant trend towards dual chamber pacing being more favourable in terms of exercise capacity (SMD -0.20, 95% CI -0.01 to -0.40). No individual studies reported a significantly more favourable outcome with single chamber ventricular pacing. Authors' conclusions: This review shows a trend towards greater effectiveness with dual chamber pacing compared to single chamber ventricular pacing, which supports the current Heart Rhythm Society Guidelines regarding atrioventricular block.