Death in Patients With Permanent Pacemaker for Sick Sinus
Background: Although more than one million patients in the United States have permanent pacemakers, little is known about their cause of death. We evaluated the cause of death in 404 patients who died in the Mode Selection Trial (MOST).
Methods: In MOST, patients received a dual-chamber pacemaker randomly programmed to either dual-chamber or ventricular pacing. The circumstances surrounding each death were reviewed by a clinical events committee, which used prospectively defined criteria to adjudicate the cause of death.
Results: A total of 2010 patients with a median age of 74 years were included. After a median follow-up of 33 months, 404 (20%) patients died, including 198 (49%) of noncardiac causes and 143 (35.4%) of cardiac causes. In 63 patients, the cause of death was unknown. Independent predictors of death through the use of a multivariable analysis were (1) demographic factors including age, male sex, and weight; (2) clinical factors including prior myocardial infarction, cardiomyopathy, New York Heart Association class III/IV, and the Charlson Comorbidity Index; and (3) scores from two measures of functional status, the Karnofsky Score and the Mini-Mental State Examination. Independent predictors of cardiovascular death were similar.
Conclusions: Patients treated with permanent pacemakers for sinus node dysfunction are elderly and have a substantial mortality rate, with more than half the classifiable deaths being noncardiac. Baseline demographic variables and scores from quality-of-life measures can identify patients with the highest risk of death.

Symptomatic sinus node dysfunction accounts for approximately half of the 225,000 permanent pacemakers implanted yearly in the United States. Symptoms of sinus node dysfunction can be prevented with permanent pacing, and recent prospective trials have demonstrated that atrial-based pacemakers are more effective than ventricular-based pacemakers at preventing atrial fibrillation, pacemaker syndrome, and mild heart failure. Mortality rates are substantial in patients with sinus node dysfunction who receive permanent pacing, with 1-year mortality rates of 5% to 10% and 5-year mortality rates of 25% to 30% reported in recent prospective trials. Despite these high mortality rates, there is little information concerning the predictors of death and the cause of death in these patients.

The recently completed Mode Selection Trial (MOST) prospectively evaluated the relative benefits of atrial-based pacemakers as compared with ventricular-based pacemakers on survival and quality of life in patients with sinus node dysfunction. We report on the causes of death in MOST patients and identify predictors of death.