Impact of a right ventricular impedance sensor on the cardiovascular responses to exercise in pacemaker dependent patients

BACKGROUND The evaluation of the heart rate (HR) response to exercise is important for the assessment of the rate response algorithm of sensor-controlled pacemakers. This study examined the effects of a right ventricular impedance sensor driven pacemaker on the cardiovascular responses to incremental exercise in pacemaker dependent patients. METHODS Twelve patients (70.5 +/- 9.5 years; 5 Females: 7 Males) implanted with an Inos(2+) closed loop stimulation (CLS) pacemaker were compared to 12 healthy age and sex matched controls (70.6 +/- 4.8 years). All subjects performed the chronotropic assessment exercise protocol (CAEP). Variables of interest included HR, cardiac output (Q), oxygen uptake (VO2) and blood pressure (BP). Data were analyzed at rest, throughout exercise and during recovery. Furthermore, patient chronotropic responses were compared to a reference chronotropic response slope for aerobic exercise. RESULTS There were no differences between groups for HR or Q response throughout exercise. At peak exercise, VO2 (mL x kg(-1) x min(-1)) was higher for the controls (p < 0.05). The patient chronotropic response slope was comparable to the CAEP reference slope from rest to both the anaerobic threshold (AT) and peak exercise. During recovery, no differences were observed between the groups for any parameters or for the HR decay slopes. CONCLUSION Up to the anaerobic threshold, the right ventricular impedance sensor driven pacemaker delivered a pacing rate that contributed to an overall cardiovascular response similar to that observed in healthy age matched subjects.