Adaptive Rate Pacing at Submaximal Exercise: The Importance of the Programmed Upper Rate

The contributions of rate response and different programmed upper rates to sub-maximal exercise were studied in 12 patients with implanted adaptive rate pacemakers (9 Meta, 3 Activitrax). Their median age was 69 years (range 33–80). All were paced from the right ventricle except for one patient with sinoatrial disease who received an atrial Meta pacemaker. In the constant rate pacing (SSI) mode, the reproducibility of a Submaximal stress test (maximum distance covered within a 12-minute walking test) was investigated by repeating the test three times. An initial training effect was obserbed between the first and the second test, but no further increase in walking distance occurred between the second and third test and the distances covered were highly reproducible (r = 0.99). The rate adaptive function was activated with the upper rate randomly programmed to 100, 125, 150, and 165 beats/min. Compared with exercise in the SSI mode, rate adaptive pacing with the upper rate programmed to 125 and 150 beats/min resulted in enhancement of exercise distance (4.7%± 1.2% and 4.4%± 1.2%, respectively, P < 0.005). Upper rates of 100 and 165 beats/min did not improve submaximal exercise performance, and at an upper rate of 165 beats/min, three patients developed complications (angina, dyspnea, and atrial fibrillation). It is concluded that the 12-minute walking test is a reproducible method to assess exercise capacity in pacemaker patients. Adaptive rate pacing improved exercise performance during daily activities, although the extent of the benefit appeared to be small and dependent on the programmed upper rate. An exercise test such as a 12-minute walking test should be performed before a high upper rate is programmed.