ATRIAL SENSING PERFORMANCE OF THE SINGLE-LEAD VDD PACEMAKER DURING EXERCISE

Objectives. The purpose of this study was to examine the atrial sensing performance of the single-lead VDD pacing system during exercise and concomitant changes in the amplitude of the atrial electrogram. Background. Studies of conventional dual-chamber pacing have demonstrated an overall reduction in the atrial signal amplitude and a variable incidence of atrial undersensing during vigorous exercise. Methods. The telemetered atrial electrogram and simultaneous surface electrocardiogram (ECG) were continuously recorded in 12 patients (mean age 70.8 years) with an implanted single-lead VDD pacing system during treadmill stress testing. The atrial signal amplitude was measured at peak exercise, and the patients were monitored for maintained atrial synchronized ventricular pacing during the entire exercise and recovery period. Results. The atrial electrographic voltage decreased an average of 19.5% (p < 0.05) during peak exercise, and the reduced P wave amplitude ranged from 6.9% to 59.4% of the preexercise values in 8 of 12 patients. Three patients showed a modest increase in atrial signal amplitude, and one patient had no change. The telemetered electrogram displayed persistent and intact atrial synchronous ventricular pacing throughout the study period. Conclusions. Despite relatively low atrial signal amplitudes at rest and further decreases during exercise, the single-lead VDD pacemaker maintains reliable atrial tracking and ventricular pacing during vigorous exercise.