First clinical results with a new temperature-controlled rate-responsive pacemaker. Comparison of Activitrax and Nova...

We examined the cardiopulmonary effects of maximum bicycle ergometer exercise in seven patients with implanted Intermedics Nova MR pacemakers for three types of pacing in a randomized sequence: VVI or AAI at 70 beats/min (SSI 70), rate-adaptive temperature-controlled pacing with the implanted Nova MR, and rate-adaptive activity-controlled pacing with a Medtronic Activitrax pacemaker taped to the chest wall, which triggered the implanted Nova MR in the VVT or AAT mode by skin electrodes. The maximum exercise tolerance was 67 W with SSI 70, 71 W with Activitrax pacing, and 91 W with Nova MR pacing; the maximum oxygen uptake as 17.6, 19.5, and 21.5 ml/min/kg, respectively. The highest heart rate achieved was 81 beats/min with SSI 70, 98 beats/min with the Activitrax, and 118 beats/min with the Nova MR on average; the mean rate increase from rest to maximum exercise was 11, 29, and 47 beats/min, respectively. With both rate-adaptive types of pacing (Nova MR and Activitrax), an increase in exercise tolerance and maximum heart rate could be achieved, but this increase was significantly more obvious with the temperature-controlled Nova MR than with the activity-controlled Activitrax. However, with a different form of exercise, for example, treadmill ergometry, the rate response of the Activitrax would presumably have been somewhat clearer.