THE ROLE OF PACING MODALITY IN DETERMINING LONG-TERM SURVIVAL IN THE SICK SINUS SYNDROME

Objective: To determine whether the atrial-based pacing modalities (''physiologic pacing'') improve survival when compared with single-chamber ventricular pacing in patients with the sick sinus syndrome. Design: Retrospective, nonrandomized study. Setting: A tertiary care teaching hospital. Patients: A total of 507 patients with a mean age of 66 years who received an initial pacemaker for the sick sinus syndrome between January 1980 and December 1989. Pacing modes were ventricular (22%), atrial (4%), and dual-chamber (74%). Measurements: Total and cardiovascular mortality rates. Mean follow-up was 66 months. Results: Independent predictors of total mortality by the Cox proportional hazards model were 1) New York Heart Association functional class (hazard ratio = 1.67/class; 95% CI, 1.31 to 2.11); 2) age (hazard ratio = 1.62/12-year increment; CI, 1.28 to 2.05); 3) peripheral vascular disease (hazard ratio = 2.21; CI, 1.42 to 3.42); 4) bundle branch block (hazard ratio = 2.04; CI, 1.33 to 3.13); 5) coronary artery disease (hazard ratio = 1.66; CI, 1.15 to 2.39); and 6) valvular heart disease (hazard ratio = 1.71; CI, 1.08 to 2.69). The same variables were independent predictors of cardiovascular mortality, with cerebrovascular disease reaching borderline statistical significance (hazard ratio = 1.69; CI, 1.00 to 2.86). Using univariate analysis, single-chamber ventricular pacing had more than 40% increased risk for both total and cardiovascular death, but the difference was of borderline statistical significance (total mortality: P = 0.053; hazard ratio = 1.43; CI, 0.99 to 2.07; cardiovascular mortality: P = 0.15; hazard ratio = 1.41; CI = 0.87 to 2.29). Conclusions: Because the role of the ventricular pacing mode as a long-term predictor of total and cardiovascular mortality remains inconclusive, a large, randomized study is necessary to confirm whether physiologic pacing provides a substantial reduction in mortality when compared with ventricular pacing.