A managed ventricular pacing (MVP) algorithm was applied, with the pacemaker working correctly (correct answer, 4). In the upper trace of the Figure, sequential pacing can be observed with an atrioventricular interval of 150ms, except for the last beat, in which the pacemaker switches to AAI mode. The MPV algorithm periodically makes such checks.1 In the lower trace, the pacemaker is working in AAI mode with atrial pacing (asterisks) when the heart rate drops below the threshold (60 bpm). An atrial pace is present after the sixth QRS: the MVP algorithm will ensure that there is no atrioventricular conduction, but in the next complex (double arrow), the pacemaker emits a safety pace, which with this model has an atrioventricular interval of 80ms. This is not ventricular capture failure (answers 1 and 2, incorrect) because there is no ventricular pace spike and at no point is failure of atrial capture observed (answer 3, incorrect).
ISSN: 1885-5857
