VALUE OF SPIROERGOMETRY AND STRESS ECHOCARDIOGRAPHY FOR OPTIMIZED PROGRAMMING OF THE UPPER TRACKING RATE OF DUAL-CHAMBER PACEMAKERS

Patients with a dual chamber pacemaker often suffer from chronic heart failure. The influence of the upper tracking rate on cardiac performa nce in patients with and without congestive heart failure is unknown. Therefore, twenty patients with a dual chamber pacemaker implanted for high degree AV block were randomly programmed to upper tracking rates of 110, 120, and 130 bpm. Oxygen uptake (VO2), work capacity, and hea rt rate were determined at the anaerobic threshold (AT) and at peak ex ercise using spiroergometry every 4 weeks. Nine patients (71 +/- 12 ye ars) had evidence for advanced heart failure (Weber C/D, group I); 11 patients (60 +/- 6 years) had no or only mild heart failure (Weber A/B , group II). Patients in group II achieved a higher mean VO2-AT at 130 bpm (17.3 +/- 3.9 ml/min/kg) than at 110 bpm (13.7 +/- 4.0 ml/min/kg; p = 0.001). Maximum oxygen uptake and work capacity at the anaerobic threshold were also significantly higher in group II with an upper tra cking rate of 130 bpm than at 110 bpm (20.5 +/- 4.5 ml/min/kg vs. 18.2 +/- 5.3 ml/min/kg, p = 0.031, and 98 +/- 29 W vs. 86 +/- 27 W, p = 0. 04). In group I, mean oxygen uptake at the anaerobic threshold (VO2-AT ) was higher at 110 bpm (11.1 +/- 4.0 ml/min/kg) than at 130 bpm, alth ough of only borderline statistical significance (9.2 +/- 2.6 ml/min/k g; p = 0.052). In group I a higher upper rate decreased VO2-AT by 24 % , whereas in group II the higher upper rate improved aerobic capacity by 26 %. Stressechocardiography (VVI pacing with a maximum tracking ra te of 130 bpm) revealed new wall motion abnormalities in all patients of group I, but only in one patient of group TI. Wall motion score ind ex increased from 1.20 +/- 0.24 at rest to 1.54 +/- 0.28 under stress (p < 0.001) in group I, but not in group II (1.00 +/- 0 vs. 1.06 +/- 0 .19; p = n. s.). Thus, carriers of dual-chamber pacemakers with no or mild heart failure (Weber A/B) benefit from higher programmed upper ra tes. In contrast, patients with more advanced heart failure (Weber C/D ) improve aerobic capacity with lower programmed upper rates. This may be caused by exercise-induced ischemia in group I as indicated by str essechocardiography.