The role of pacing modality in determining long-term survival in the sick sinus syndrome

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.

Retrospective, nonrandomized study.

A tertiary care teaching hospital.

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%).

Total and cardiovascular mortality rates. Mean follow-up was 66 months.

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% Cl, 1.31 to 2.11); 2) age (hazard ratio = 1.62/12-year increment; Cl, 1.28 to 2.05); 3) peripheral vascular disease (hazard ratio = 2.21; Cl, 1.42 to 3.42); 4) bundle branch block (hazard ratio = 2.04; Cl, 1.33 to 3.13); 5) coronary artery disease (hazard ratio = 1.66; Cl, 1.15 to 2.39); and 6) valvular heart disease (hazard ratio = 1.71; Cl, 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; Cl, 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; Cl, 0.99 to 2.07; cardiovascular mortality: P = 0.15; hazard ratio = 1.41; Cl = 0.87 to 2.29).

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.