This 63-year-old man presented with a history of paroxysmal atrial fibrillation (AF) and complete right bundle branch block on the electrocardiogram (ECG). He suffered 3 episodes of syncope without prodrome. An electrophysiologic study revealed an 82-ms HV interval, prompting the implantation of an Adapta® dual chamber pacemaker. Both pacing leads were properly positioned and associated with normal impedance, and satisfactory sensing and capture thresholds. The pacemaker was interrogated 3 days after the implant and recordings were obtained during the programming of various pacing modes. This first tracing was recorded in ODO mode.
Tracing 9a: MVP mode programmed at 70 bpm;
Tracing 9b: MVP mode programmed at 60 bpm;
Tracing 9c: programming unchanged;
Tracing 9d: programming unchanged;
The appreciation of the adverse effects of right ventricular pacing prompted the development of an AAI platform that automatically switches to DDD mode in presence of AV block, and conversely when conduction returns. These various tracings allow the definition of the different characteristics of the MVP mode:
1) on the first tracing (9a), the main advantage of this algorithm seems evident. Compared with tracing no 8, the programming of this algorithm decreased the proportion of pacing from 100 to 0%. On the long term, this should confer benefits from the standpoint of ventricular remodelling and development of atrial arrhythmias. Percent ventricular pacing is, therefore, an important aspect of the follow-up of patients suffering from sinus node dysfunction, with a view to decrease to a maximum all unnecessary ventricular pacing. It is noteworthy that, on this tracing, the PR interval is relatively prolonged (approximately 300 ms after a paced P wave). In patients with a prolonged PR at rest and during exercise, the pacemaker remains in AAI mode without switching to DDD mode. In presence of symptoms associated with prolongation of the PR interval during exercise, programming to DDD mode seems desirable.
2) on the second tracing (9b), a single blocked atrial event does not prompt a switch to DDD mode. Ventricular safety pacing occurs 80 ms after the following paced atrial event. The longest ventricular pause accepted by the pacemaker corresponds to one half of the slowest programmed rate. To preclude excessively long pauses, it is preferable to not program an excessively slow backup rate.
3) On the third tracing (3c), switch to DDD mode occurs upon repeated interruptions of AV conduction. This relatively rapid switch to DDD mode prevents a succession of pauses and of adverse AP-VP pacing, because associated with a short AV delay (occasionally poorly tolerated by the patient).
4) the last tracing (9d) shows a first confirmation of AV conduction, 1 min after switch to DDD mode. In the first cycle in AAI mode, AV conduction is present (AP -S) and the device switches again to AAI mode.
