Switch between AAI and DDD mode pacing-What is the mechanism?

The electrocardiogram (ECG) interpretation in patients with implantable pacemaker is often a perplexing problem. The difficulty in the device evaluation increases in the presence of novel timing cycles and additional functions. Authors describe a special function frequently encountered in Medtronic dual-chamber pacemakers and implantable cardioverter-defibrillator devices called managed ventricular pacing (MVP) and demonstrate its performance in the patient with undersensing episodes in ventricular channel. Intermittent ventricular undersensing in the device with MVP feature turned on caused repetitive mode switches between AAI and DDD mode. This report shows unexceptional occurrence of tricky ECG findings in patient with Medtronic dual-chamber device.