Rate responsive pacemakers: assessment after two years.

Rate responsive pacemakers (RRPM) for patients without sufficient response of the heart rate (HR) to exercise represent an alternative to improve cardiac output (CO) and capacity for exercise via an increase of HR. From 1983 until December 1985, we implanted 30 QT-related (TX), 25 respiratory dependent (RDP), and 35 body activity directed (ACT) pacemakers. The follow-up examination consisted of Holter-ECG, treadmill and/or bicycle workload, and determination of CO (TX: thermodilution technique, n = 11; 6 months after implantation. RDP: equilibrium radionuclide ventriculography, n = 13; 1 month after implantation). The capacity for exercise of patients with ACT was studied using a climbing step. Adaptation of HR could be achieved with TX, RDP, and ACT. There was a significant increase in CO during exercise TX or RDP versus VVI-mode (TX: delta = 1.7 l/min, RDP: delta = 2.1 l/min). Although all systems exhibited weak points, RRPM are reliable devices. We abide by using these pacemakers.