Journal of the American College of Cardiology
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J. Am. Coll. Cardiol. · Nov 1989
Randomized Controlled Trial Clinical TrialRate-modulated cardiac pacing based on transthoracic impedance measurements of minute ventilation: correlation with exercise gas exchange.
The relation of pacing rate to physiologic variables of metabolic demand was examined in 10 consecutive patients with a minute ventilation-sensing, rate-modulating ventricular pacemaker implanted for complete heart block. All patients had paroxysmal (seven patients) or chronic (three patients) atrial fibrillation and were referred for catheter ablation of the atrioventricular junction. Treadmill exercise testing with measurement of expired gas exchange and respiratory flow was performed before ablation and 4 weeks after pacemaker implantation, with the pacemaker programmed to both the fixed-rate VVI and rate-modulating minute ventilation VVIR pacing modes in random sequence. ⋯ The mean exercise duration increased from 8.3 +/- 2.8 min in the fixed rate pacing mode to 10.2 +/- 3.4 min in the rate-modulating, minute ventilation mode (p = 0.0001). The maximal VO2 increased from 13.4 +/- 3.4 to 16.3 +/- 4.1 cc/kg per min (p = 0.0004). The maximal heart rate achieved in the minute ventilation pacing mode was 136 +/- 9.7 beats/min, similar to that observed in the patient's intrinsic cardiac rhythm before ablation (134.9 +/- 30.1 beats/min, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)