LONG-TIME BENEFIT OF RATE ADAPTATION - RESULTS IN SPIROERGOMETRY AND SUBMAXIMAL EXERCISE

It is well known that rate adaptive pacing acutely improves exercise c apacity. However, there is a lack of studies dealing with the long tim e effect of rate adaptation. Thus we examined 11 patients (age 63 + 11 years) with a rate adaptive single chamber pacemaker (Excel VR) in th e SSI or SSIR mode 4 weeks after implantation at the earliest and agai n 4 weeks after switching to the SSI or SSIR mode, respectively. Patie nts did treadmill spiroergometry (CAEP protocol) and submaximal exerci ses (6-minute walk, stair climbing). Results: Whenever in all tests si gnificantly higher heart rates were found with the SSIR mode, improved exercise capacity was only seen in spiroergometry. This was limited t o patients with a maximal spontaneous exercise heart rate < 100 bpm in the SSI mode. In the SSIR mode oxygen uptake at the anaerobic thresho ld improved by 14% (VO2 AT, p < 0.05), exercise capacity by 40% (p = 0 .12) and exercise duration at the AT by 21% (p < 0.005). Six patients felt better in the SSIR mode and 5 patients did not feel any differenc e. The patients who preferred the rate adaptation had markedly higher exercise heart rates with the SSIR as compared with the SSI mode. Conc lusion: Only patients with a clear chronotropic incompetence which may be defined by a maximal exercise heart rate below 90-100 bpm have lon g time benefit from rate adaptive pacing.