What is the comparison of single- and dual-chamber pacemakers for the treatment of sinus node dysfunction (SND)?

Updated: Nov 30, 2018
  • Author: Bharat K Kantharia, MD, FRCP, FAHA, FACC, FESC, FHRS; Chief Editor: Mikhael F El-Chami, MD  more...
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In patients with SND, the annual incidence of complete heart block is about 0.6%. [33] In the United States, the implantation of dual-chamber pacemakers is preferred in practice because their use anticipates the possible subsequent development of conducting system dysfunction.

This practice is supported by data from the Danish Multicenter Randomized Trial on Single Lead Atrial Pacing versus Dual Chamber Pacing in Sick Sinus Syndrome (DANPACE) trial, in which 9.3% of patients with single-lead atrial pacing (AAI) required upgrade to a dual-chamber pacemaker (DDD) over 5.4 years of follow-up due to new development of significant atrioventricular (AV) conduction abnormalities. [34] This was necessary despite the fact that these patients had no significant intraventricular conduction abnormality, had PR intervals below 260 ms, and had no Wenckebach AV block with atrial pacing at 100 bpm at baseline. In addition, the incidence of atrial fibrillation (AF) was higher in patients in AAI mode than those in DDD mode. However, no significant mortality difference was noted between the groups in AAI and DDD modes. [34]

Arguably, a single-chamber atrial pacemaker with AAI mode is an acceptable alternative in patients with SND and normal AV and intraventricular conduction because of the added expense of, and the potential for, more lead extraction with a dual-chamber pacemaker.

In patients with SND and known AV conduction abnormality (including bundle branch block and bifascicular block), a dual-chamber pacemaker should be used due to the high risk of AV block (about 36% in a 5-year follow-up study).

In a collaborative pooled-analysis of 10 randomized trials (n = 6639) to evaluate the effect of existing pacing strategies on the risk of postimplantation AF and heart failure events in SND patients, Chen et al stratified the pooled-analysis into two subsets—AAI versus DDD, and minimal ventricular pacing (MinVP) versus DDD—and found that although composite AF and heart failure (HF) events were similar in the AAI versus DDD subset, there was a substantially reduced risk of composite AF and HF in the MinVP group receiving pacemaker as primary treatment. [35] Over the long term, however, the rate of AF and HF was similar in the MinVP versus DDD subset of patients who were scheduled for device replacement. The investigators indicated their findings supported the use of MinVP over conventional DDD in improving clinical outcomes for SND patients who received a pacemaker as primary treatment. [35]

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