The effect of atrial-based pacing on exercise capacity as measured by the 6-minute walk test: a substudy of the Canadian Trial of Physiological Pacing (CTOPP).
BACKGROUND
Although several randomized trials have detected no reduction in major cardiovascular events with the routine use of dual-chamber as opposed to ventricular pacemakers, many individuals continue to advocate their use as a means of improving exercise capacity.


METHODS
The Canadian Trial of Physiological Pacing (CTOPP) trial is the largest trial comparing ventricular pacing to atrial-based pacing (atrial or dual-chamber) in patients with bradycardia. All patients in this trial were asked to complete a 6-minute hall walk test (6MWT) at the time of their first study follow-up. The distance walked in 6 minutes and the patient's heart rate before and immediately after the walk were recorded.


RESULTS
Of the 2568 patients in the CTOPP, 76% completed the 6MWT. The mean distance walked was 350 +/- 127 m in the ventricular pacing group and 356 +/- 127 m in the atrial-based group (P = NS). Similarly, there was no difference in the change in heart rate between the two groups (17 +/- 13 vs. 18 +/- 12 bpm: P = NS). However, among patients with an unpaced heart rate of </=60 bpm, patients assigned to atrial-based pacing walked farther than those randomized to ventricular pacing (361 +/- 127 vs. 343 +/- 121 m; P = .04). This was not associated with a difference in heart rate. The use of rate-adaptive pacing, irrespective of the pacing mode, resulted in a greater increase in heart rate with the 6MWT but no increase in the total distance walked.


CONCLUSIONS
The routine use of atrial-based pacemakers, instead of ventricular pacemakers, does not improve exercise capacity, as measured by the 6MWT. However, patients with an unpaced heart rate of </=60 bpm may achieve a modest increase in their exercise capacity with atrial-based pacing.
Baranchuk
Adrian
A
Queen's University, Kingston, Ontario, Canada.
Healey
Jeff S
JS
Thorpe
Kevin E
KE
Morillo
Carlos A
CA
Nair
Girish
G
Crystal
Eugene
E
Kerr
Charles R
CR
Connolly
Stuart J
SJ
D000368:Aged; D000369:Aged, 80 and over; D001919:Bradycardia / Q000628:therapy*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006325:Heart Atria; D006801:Humans; D008297:Male; D008875:Middle Aged; D011788:Quality of Life