July 14, 2005
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)