Incidence of atrial fibrillation and thromboembolism in a randomised trial of atrial versus dual chamber pacing in 177 patients with sick sinus syndrome

Abstract

Objective: To analyse the occurrence of atrial fibrillation (AF) and thromboembolism in a randomised comparison of rate adaptive single chamber atrial pacing (AAIR) and dual chamber pacing (DDDR) in patients with sick sinus syndrome and normal atrioventricular (AV) conduction, in which left atrial dilatation and decreased left ventricular fractional shortening had been observed in the DDDR group.

Methods: 177 consecutive patients with sick sinus syndrome (mean (SD) age 74 (9) years, 104 women) were randomly assigned to treatment with one of three pacemakers: AAIR (n = 54), DDDR with a short rate adaptive AV delay (n = 60) (DDDR-s); or DDDR with a fixed long AV delay (n = 63) (DDDR-l). Analysis was intention to treat.

Results: Mean follow up was 2.9 (1.1) years. AF at one or more ambulatory visits was significantly less common in the AAIR group (4 (7.4%) v 14 (23.3%) in the DDDR-s group v 11 (17.5%) in the DDDR-l group; p = 0.03, log rank test). The risk of developing AF in the AAIR group compared with the DDDR-s group was significantly decreased after adjustment for brady-tachy syndrome in a Cox regression analysis (relative risk 0.27, 95% confidence interval (CI) 0.09 to 0.83, p = 0.02). The benefit of AAIR was highest among patients with brady-tachy syndrome. Brady-tachy syndrome and a thromboembolic event before pacemaker implantation were independent predictors of thromboembolism during follow up (relative risk 7.5, 95% CI 1.6 to 36.2, p = 0.01, and relative risk 4.7, 95% CI 1.2 to 17.9, p = 0.02, respectively).

Conclusions: During a mean follow up of 2.9 years AAIR was associated with significantly less AF. The beneficial effect of AAIR was still significant after adjustment for brady-tachy syndrome. Brady-tachy syndrome was associated with an increased risk of thromboembolism.

Figure 1

Numbers of patients in the study population and in the three randomisation groups are listed together with the numbers of events during follow up in each randomisation group. The patients are further divided into groups with (+BTS) and without brady-tachy syndrome (−BTS). AAIR, rate adaptive single chamber atrial pacing; AF, atrial fibrillation; DDDR-l, rate adaptive dual chamber pacing with the pacemaker programmed with a fixed atrioventricular (AV) delay of 300 ms; DDDR-s, rate adaptive dual chamber pacing with the pacemaker programmed with a rate adaptive AV delay ⩽ 150 ms and ventricular capture; TE, thromboembolic event.

Figure 2

Kaplan-Meier curves of the proportion of patients in each randomisation group without AF during follow up plotted separately for patients with and without brady-tachy syndrome. AF was diagnosed only by standard 12 lead ECG at planned follow up visits, not between these visits.

Figure 3

Kaplan-Meier plots of freedom from thromboembolic events during follow up for patients with (+BTS) and without brady-tachy syndrome (−BTS).