The Effects of Rate-Adaptive Atrial Pacing versus Ventricular Backup Pacing on Exercise Capacity in Patients with Left Ventricular Dysfunction

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New York Medical College

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BACKGROUND: Atrial rate-adaptive pacing may improve cardiopulmonary reserve in patients with left ventricular dysfunction.

METHODS: A randomized, blinded, single-crossover design enrolled dual-chamber implantable defibrillator recipients without pacing indications and an ejection fraction < or =40% to undergo cardiopulmonary exercise treadmill stress testing in both atrial rate-adaptive pacing (AAIR) and ventricular demand pacing (VVI) pacing modes. The primary endpoint was change in peak oxygen consumption (VO(2)). Secondary endpoints were changes in anaerobic threshold, perceived exertion, exercise duration, and peak blood pressure.

RESULTS: Ten patients, nine males, eight with New York Heart Association class I, mean ejection fraction 24 +/- 7%, were analyzed. Baseline VO(2) was 3.6 +/- 0.5 mL/kg/min. Heart rate at peak exercise was significantly higher during AAIR versus VVI pacing (142 +/- 18 vs 130 +/- 23 bpm; P = 0.05). However, there was no difference in peak VO(2) (AAIR 23.7 +/- 6.1 vs VVI 23.8 +/- 6.3 mL/kg/min; P = 0.8), anaerobic threshold (AAIR 1.3 +/- 0.3 vs VVI 1.2 +/- 0.2 L/min; P = 0.11), rate of perceived exertion (AAIR 7.3 +/- 1.5 vs VVI 7.8 +/- 1.2; P = 0.46), exercise duration (AAIR 15 minutes, 46 seconds +/- 2 minutes, 54 seconds vs VVI 16 minutes, 3 seconds +/- 2 minutes, 48 seconds; P = 0.38), or peak systolic blood pressure (AAIR 155 +/- 22 vs VVI 153 +/- 21; P = 0.61) between the two pacing modes.

CONCLUSION: In this study, AAIR pacing did not improve peak VO(2,) anaerobic threshold, rate of perceived exertion, or exercise duration compared to VVI backup pacing in patients with left ventricular dysfunction and no pacing indications.

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