Incidence and Predictors of Loss of Pacing in the Atrium in Patients with Sick Sinus Syndrome

Atrial and dual-chamber pacemakers may be associated with reduced morbidity in patients with the sick sinus syndrome (SSS). In some patients, however, subsequent development of chronic atrial fibrillation or atrial lead failure make long-term pacing in the atrium not feasible. We analyzed the incidence and predictors of loss of atrial pacing in 395 consecutive patients with SSS (376 with dual-chamber pacemakers and 19 with single-chamber atrial pacemakers). None of them was in established atrial fibrillation at time of implant. Patients were followed-up for 55 ± 35 months. Actuarial survival of effective atrial pacing was 92.5% at 1 year, 85% at 5 years, and 76.5% at 10 years. Overall, 60 patients lost atrial pacing. The most frequent cause was the development of chronic atrial fibrillation (53 patients). By multivariate analysis (Cox proportional-hazards model), independent predictors of Joss of pacing in the atrium were preimplant episodes of paroxysmal atrial fibrillation (PAF) lasting more than 1 hour (P < 0.001; hazard ratio (HR) = 4.3); prior history of PAF for more than 5 years (P < 0.001; HR = 2.67; and endocardial P wave < 2 mV (P = 0.014; HR = 1.96). In a subgroup of patients (n = 187) who had echocardiograms, a left atrium > 50 mm was also an independent predictor of loss of atrial pacing (P = 0.028; HR = 2.28). Conclusions: 1) most patients with SSS can maintain long-term atrial pacing; 2) loss of pacing in the atrium is related to the previous history of PAF, left atrial enlargement, and low amplitude of the endocardial P wave at implant; and 3) patients with these risks variables are less than ideal candidates for atrial pacing modes. In them, the implant of DDDR units might be indicated, to provide wide flexibility in case reprogramming to a ventricular pacing mode is required.