Long-Term Pacemaker Therapy for Sick Sinus Syndrome
December 1, 1997 2 minutes read
Long-Term Pacemaker Therapy for Sick Sinus Syndrome
ABSTRACT & COMMENTARY
Synopsis: Atrial as compared to ventricular single chamber pacing for sick sinus syndrome was associated with less chronic atrial fibrillation, fewer systemic emboli, less heart failure, and a higher survival.
Source: Andersen HR, et al. Lancet 1997;350: 1210-1216.
Andersen and colleagues previously showed in a randomized trial comparing single chamber atrial to ventricular pacing in sick sinus syndrome (SSS) that atrial pacing was associated with less atrial fibrillation and thromboembolism. The three-year follow-up did not show differences in heart failure or mortality. Thus, the investigators continued to follow the 225 patients for up to eight years. In the atrial group, 39 patients experienced a cardiac death vs. 57 patients in the ventricular group (OR, 0.66; CI 0.44-0.99; P = 0.05). Chronic atrial fibrillation incidence continued to be lower in the atrial group, with nine vs. 22 patients (P < 0.02), as were thromboembolic events, with 13 vs. 26 patients (P < 0.03). Also, heart failure was less (P < 0.05). Atrioventricular block occurred in four patients in the atrial group (annual risk < 1%), and pacemaker lead problems were more common in the atrial group (12 vs 2). Andersen et al conclude that atrial, as compared to ventricular single chamber pacing for SSS was associated with less chronic atrial fibrillation, fewer systemic emboli, less heart failure, and a higher survival. Thus, patients with SSS should be treated with atrial pacing.
COMMENT BY MICHAEL H. CRAWFORD, MD
This is an interesting and provocative study for U.S. cardiologists. The results clearly show the long-term benefits of atrial pacing for SSS. This conclusion should no longer be in doubt. The major issue for U.S. cardiologists is whether to implant a dual chamber device. Andersen et al argue that "unfavorable stimulation" of the left ventricle may, over time, lead to LV dysfunction and heart failure. Since dual chamber pacers will deliver some ventricular stimulation, patients with DDD pacers may do as poorly as the single chamber ventricular pacemaker patients in this trial. However, this is not proven. Also, they argue that the low incidence of complete heart block (< 1%/yr) is not worth the extra expense in all SSS patients. They do acknowledge that patients at higher risk of complete heart block would be candidates for DDD pacing, such as patients with SSS and right bundle branch block.
Another interesting aspect of the study was the lower incidence of thromboembolism with atrial pacing, which was one of the strongest benefits on multivariate testing. This benefit was not completely explained by atrial fibrillation prevention, as patients without atrial fibrillation also had fewer emboli with atrial pacing. The patients may have had intermittent, unrecognized atrial fibrillation; Andersen et al suggest that ventricular pacing may lead to ventricular thrombus development. Finally, Andersen et al note that few of their patients were on anticoagulation despite indications for it. Perhaps because the patients were older (average 71 years), less anticoagulation was given. Regardless, a more aggressive anticoagulation policy may have reduced thromboemboli to the point that the pacing chamber may not have been as important.
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