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)
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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. CONCLUSION: 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.
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