63-year-old man with a history of paroxysmal atrial fibrillation; full right bundle branch block pattern on the electrocardiogram; 3 episodes of sudden syncope; electrophysiological study with HV interval measurement at 82 ms; implantation of an Adapta dual-chamber pacemaker; the 2 leads are well positioned with normal pacing impedance, proper sensing and satisfactory pacing thresholds; 3 days after implantation, pacemaker control; programming of various pacing modes and recording of tracings; for this first tracing, programming in ODO mode.
Programming of the MVP mode with switching due to long PR (programmed limit value 350 ms); progressive increase in the pacing rate and analysis of atrioventricular conduction;
When the PR interval is extremely prolonged, the physiological activation/contraction sequence between atria and ventricles is no longer observed, leading to a contraction of the atria while the mitral valves are closed, which can be associated with the presence of symptoms. These tracings illustrate the new functionality of the MVP algorithm with the possibility of switching when the PR interval exceeds a programmable value. The device measures the PR interval (atrial sensing, AS-VS) or AR interval (atrial pacing, AP-VS) averaged over 4 consecutive cycles. If the average of the last four PR or AR (no difference in value whether the atrium is sensed or paced) exceeds this limit, the device switches to DDD(R) mode. The first atrioventricular conduction verification occurs 1 minute after switching to the DDD(R) mode. During this verification, if the PR or AR interval remains prolonged and greater than the programmed value, the device continues in DDD(R) mode. The interval between each conduction control is then doubled (2, 4, 8… minutes to a maximum of 16 hours). For this patient, we can see that the first version of the algorithm would not have led to a switching in DDD mode (absence of blocked P waves) and that at the time of conduction verification, it would have returned to ADI mode (long AR but 1/1 conduction).
By default, the long PR function of the MVP algorithm is programmed to OFF. It is probably necessary to reserve the programming of this feature for patients with symptoms on exertion. Indeed, a similar value of PR interval duration may be acceptable at rest but problematic on exertion. A value of 300 to 350 ms for the PR limit value probably corresponds to a good compromise for limiting the occurrence of symptoms on exertion while avoiding iterative commutations, even if an individual optimization of this parameter can be proposed.
