Evaluation by cardiopulmonary exercise test of DDDR versus DDD pacing

In eight patients (age 62 +/- 6 years) a DDDR pacemaker was implanted for sick sinus syndrome (three cases) or second- and third-degree AV block (five cases). In five subjects chronotropic incompetence (maximal heart rate on effort < 110 beats/min) was present before implantation. One month after implantation the patients were randomized to DDDR or DDD pacing for 3 weeks each, with subsequent crossover, and at the end of each period a symptom limited cardiopulmonary exercise test (25 watts/2 min) was performed and the patients were requested to fill a symptoms questionnaire.

DDDR pacing, compared to DDD, was associated with higher maximal heart rates (127 +/- 20 vs 110 +/- 27 beats/min, P < 0.02), higher [VO2 max (25.4 +/- 6.1 vs 21.5 +/- 7.8 mL/kg/per min, P < 0.03) and higher VO2 at the anaerobic threshold (20.3 +/- 5.0 vs 15.8 +/- 4.9 mL/kg per min, P < 0.03), without significant differences in mean exercise time (526 +/- 193 vs 472 +/- 216 sec, NS). The increase in VO2 max obtained in DDDR versus DDD was significantly related to the increase in maximal heart rate (r = 0.72, P < 0.05) and the increase in VO2 at the anaerobic threshold obtained in DDDR versus DDD was related to the increase in heart rate at the anaerobic threshold (r = 0.81, P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)