Long-term follow-up of patients from a randomised trial of atrial versus ventricular pacing for sick-sinus syndrome.

BACKGROUND: In a previous study of 225 patients with sick-sinus syndrome randomised to either single-chamber atrial pacing (n=110) or single-chamber ventricular pacing (n=115), we found that after a mean follow-up of 3.3 years, atrial pacing was associated with significantly less atrial fibrillation and thromboembolism whereas there was no significant difference in mortality and heart failure between the two groups. We aimed to find out whether this beneficial effect of atrial pacing is maintained during extended follow-up of up to 8 years.

METHODS: Follow-up visits for all patients were at 3 months, 12 months, then once a year at which patients had a physical examination, ECG recording, and pacemaker check-up. Endpoints were mortality, cardiovascular death, atrial fibrillation, thromboembolic events, heart failure, and atrioventricular block. Data was analysed on Dec 31, 1996.

FINDINGS: At long-term follow-up, 39 patients from the atrial group had died versus 57 from the ventricular group (relative risk 0.66 [95% CI 0.44-0.99]; p=0.045). 19 patients from the atrial group and 39 patients from the ventricular group died from a cardiovascular cause (0.47 [0.27-0.82]; p=0.0065). The cumulative incidences of atrial fibrillation and chronic atrial fibrillation were also significantly lower in the atrial group than in the ventricular group (0.54 [0.33-0.89], p=0.012 and 0.35 [0.16-0.76], p=0.004, respectively). Thromboembolic events occurred in 13 patients in the atrial group and 26 in the ventricular group (0.47 [0.24-0.92], p=0.023). Heart failure was less severe in the atrial group than in the ventricular group (p<0.05). In multivariate analysis, atrial pacing was significantly associated with freedom from thromboembolic events (0.47 [0.24-0.92], p=0.028) and survival from cardiovascular death (0.52 [0.30-0.91], p=0.022), but no longer with overall survival (0.71 [0.46-1.08], p=0.11) or chronic atrial fibrillation (0.45 [0.20-1.05], p=0.063). Atrioventricular block occurred in four patients in the atrial group (0.6% annual risk).

INTERPRETATION: The beneficial effect of atrial pacing found in our previous study is enhanced substantially over time. Patients with sick-sinus syndrome should be treated with an atrial rather than ventricular-pacing system because after long-term follow-up, atrial pacing is associated with a significantly higher survival, less atrial fibrillation, fewer thromboembolic complications, less heart failure, and a low-risk of atrioventricular block.