Diagnosis of atrial undersensing in dual chamber pacemakers: Impact of autodiagnostic features

Atrial undersensing occurs in a considerable number of patients, both with single lead VDD pacemakers and with DDD devices. The aim of this study was to investigate the diagnostic efficacy of electrocardiographic methods and autodiagnostic pacemaker features to detect a trial sensing dysfunction. Tw o hundred and thirty-one patients with AV block received single lead VDD pa cemakers or DDD devices. Atrial sensitivity was programmed to 0.1 or 0.18 i n VDD devices and to 0.5 mV in DDD devices; the rate limits were set to 40 and 160 beats/min. Twelve-lead ECG recording for 1 minute during deep respi ration and change of body position, 24-hour Holter ECG recording, and tread mill exercise were performed 2 weeks and 15 months after pacemaker implanta tion. AV synchrony and, if available, P wave amplitude histogram were sampl ed by autodiagnostic pacemaker features and compared to electrocardiographi c findings. Atrial undersensing was assumed, if AV synchrony was below 100% or if minimal P wave amplitude (PWA) was equal to the programmed atrial se nsitivity. Intermittent atrial undersensing occurred in 20.7% of patients. The diagnostic sensitivities of the various methods used to detect atrial s ensing failures were: 24-hour Holter monitoring 97.5%, P wave amplitude his togram 90.0%, stored AV synchrony 68.0% without significant difference betw een the various devices, treadmill exercise testing 58.8%, and 12-lead ECG recording 21.3%. In one patient, atrial undersensing was exclusively detect ed by exercise testing. In conclusion, autodiagnostic pacemaker features fa cilitate the evaluation of atrial sensing performance. However, to exclude intermittent atrial malsensing, routine Holter monitoring and treadmill exe rcise are still needed.