By Sahar Bedrood B.S. and Asher Kimchi M.D.

Leicester, UK - Cardiac pacing is a treatment for high-grade atrioventricular heart block. There is a debate about whether Single-Chamber or Dual-Chamber pacing is the most appropriate form of treatment. While dual-chamber is associated with lower incidence of atrial fibrillation, stroke and heart failure in non-randomized studies, Dr. William Toff et al from the University of Leicester, UK conducted a randomized, parallel-group trial comparing patients who received single-chamber versus double-chamber pacers. The study, published in the July 14, 2005 issue of The New England Journal of Medicine, indicates no significant difference between the group with dingle-chamber pacing and that with dual-chamber pacing in the rates of atrial fibrillation, heart failure or a composite of stroke, transient ischemic attack or other thromboembolism. 

In a multi-center, randomized, parallel-group trial, 2021 patients 70 years of age or older who were undergoing their first pacemaker implant for high-grade atrioventricular block were randomly assigned to receive a single-chamber ventricular pacemaker (1009 patients) or a dual-chamber pacemaker (1012 patients). In the single-chamber group, patients were randomly assigned to receive either fixed-rate pacing (504) or rate-adaptive pacing (505 patients). The primary outcome was death from all causes. Secondary outcomes included atrial fibrillation, heart failure, and a composite of stroke, transient ischemic attack or other thromboembolism.  

The median follow-up was 4.6 years for mortality and 3 years for other cardiovascular events. The mean annual mortality rate was 7.2 percent in the single-chamber group and 7.4 percent in the dual-chamber group (hazard ratio, 0.96; 95 percent confidence interval, 0.83 to 1.11). Thus, no significant differences between the group with single-chamber pacing and that with dual-chamber pacing in rates of atrial fibrillation, heart failure, and a composite of stroke, transient ischemic attack or other thromboembolism.  

It was thus concluded from the study that in elderly patients with high-grade atrioventricular block, the pacing mode does not influence the rate of death from all causes during the first five years or the incidence of cardiovascular events during the first three years after implantation of a pacemaker. 

Co-authors: John Camm, M.D., J. Douglas Skehan, M.B, B.S., for the United Kingdom Pacing and Cardiovascular Events (UKPACE) Trial Investigators