[Chronic frequency-adaptive pacemaker therapy in patients with heart failure].

Twenty patients (complete AV block n = 13, sick sinus syndrome n = 4 (replacement of a VVI system), bradyarrhythmia n = 3) with rate-adaptive pacemakers (respiration volume guided n = 10, QT-driven n = 1, dual sensor (QT/activity) system n = 9) were randomly assessed by ergospirometry after 4 weeks of VVI- (70 bpm), VVIR1-(70-110 bpm, low upper rate) and VVIR2-pacing (70-130 bpm, high upper rate). Oxygen uptake (VO2), work load (W), and heart rate were determined at peak exercise (max) and at the anaerobic threshold (AT). In the whole population, rate adaptation led to a significantly higher VO2-max than VVI-pacing for both VVIR1- (15.5 +/- 5.1/12.6 +/- 4.1 ml/kg/min, 28 +/- 37%, p < 0.01) and VVIR2-pacing (14.8 +/- 4.4/12.6 +/- 4.1 ml/kg/min, 20 +/- 23%, p < 0.01). At the AT, however, VO2 was significantly improved only by the VVIR1 mode (low upper rate, 9.8 +/- 2.5/8.0 +/- 2.1 ml/kg/min, 28 +/- 36%, p < 0.01). Regarding only patients with moderately limited exercise capacities (Weber class C, n = 11), rate adaptive VVIR1 and VVIR2 pacing could not produce a significant increase of VO2-max and VO2-AT. In contrast, patients with severely reduced exercise capacities (Weber class D, n = 9) significantly profited from the rate adaptation, but only in the VVIR1 mode (VO2-max 48 +/- 45%, VO2-AT 51 +/- 38%, p < 0.01). Thus, in the whole population an increase of oxygen uptake and of exercise workload at the anaerobic threshold could only be achieved by pacing with the low upper rate of 110 bpm. By this, particularly patients with heart failure and a severely limited exercise tolerance (Weber D) had a significant benefit. Therefore, the upper rate should be programmed in a lower range in patients with heart failure, at least for rate-adaptive ventricular pacemaker systems.