Atrial sensing performance of AV universal pacemakers during exercise.

To investigate the atrial sensing function of dual chamber pacemakers during exercise, we studied 57 patients aged 12 to 81 years (m = 65). They were paced for sinoatrial disorders (n = 15), second or third degree AV block (n = 37), or binodal disease (n = 11). The examination was performed 3-24 months (m = 11) after pacemaker implantation. Individual sensing thresholds were determined at rest in the supine position, and proper detection of atrial signals at the programmed sensitivity level was verified during a period of 5-9 minutes (m = 5.8). Without a change in the program of the unit, symptom-limited bicycle ergometry was performed at a maximum load of 25-200 Watts (m = 95) and 6-channel chest wall electrocardiograms were continuously recorded throughout the test, including recovery. During exercise, 25/57 patients (44%) exhibited poor atrial sensing of the pulse generator; after termination of exercise in 16 of the 25 patients, proper atrial sensing resumed within 1 to 7 minutes of recovery. In the remaining nine cases, ergometry was continued after lowering the sensitivity threshold to half the initial setting or, depending on the pacemaker model, by a value of 0.4 mV. This resulted in normal function of the pulse generator in all patients but one, who needed a sensitivity adjustment of another 0.4 mV. In a subgroup of 25 patients, telemetric atrial electrogram recordings were monitored during ergometry, 19 of which could be evaluated quantitatively. Besides random atrial signal variations, presumably due to ectopic beats or runs, a systematic decrease of the peak-to-peak amplitude by 0.1 to 1.6 mV (3-30%) was observed in 16/19 patients during exercise. Mean signal reduction amounted to 11.8% and was statistically significant at the 0.1% level. It is concluded from these findings that, besides testing of atrial sensing at rest, the follow-up of dual chamber pacemakers should include an exercise test.