LONG-TERM FOLLOW-UP OF PATIENTS FROM A RANDOMIZED TRIAL OF ATRIAL VERSUS VENTRICULAR PACING FOR SICK-SINUS SYNDROME

Background In a previous study of 225 patients with sick-sinus syndrom e 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 significa nt difference in mortality and heart failure between the two groups. W e 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 y ear at which patients had a physical examination, ECG recording, and p acemaker check-up. Endpoints were mortality, cardiovascular death, atr ial fibrillation, thromboembolic events, heart failure, and atrioventr icular 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 ventricul ar 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 patient s 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 paci ng was significantly associated with freedom from thromboembolic event s (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 atr ial group (0.6% annual risk).Interpretation The beneficial effect of a trial pacing found in our previous study is enhanced substantially ove r time. Patients with sick-sinus syndrome should be treated with an at rial rather than ventricular-pacing system because after long-term fol low-up, atrial pacing is associated with a significantly higher surviv al, less atrial fibrillation, fewer thromboembolic complications, less heart failure, and a low-risk of atrioventricular block.