Triggered modes
Patient
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.
Trace
Tracing 3a: programming in AAT mode 40 beats/minute;
- proper sensing of spontaneous atrial activity triggering an atrial pacing (TP for Triggered Pacing);
- correct sensing of the atrial extrasystole triggering an atrial pacing (TP);
Tracing 3b: programming in AAT mode 60 beats/minute;
- atrial pacing at the base rate (AP);
- proper sensing of the atrial extrasystole triggering an atrial pacing (TP);
Tracing 3c: programming in VVT mode 40 beats/minute;
- proper sensing of spontaneous ventricular activity and ventricular pacing (TP); absence of capture and electrocardiographic pattern similar to that of a spontaneous pattern;
- non-conducted atrial extrasystole with compensatory rest; at the end of the escape interval (1500 ms after ventricular sensing), ventricular pacing at the base rate (VP);
- fusion between the spontaneous ventricle and the paced ventricle.
Comments
When the VVT mode is programmed, pacing occurs at the programmed minimum rate, although a sensed non-refractory event triggers an immediate pacing in the absolute refractory period of the ventricular myocardium. This operational mode therefore corresponds to the opposite of the VVI mode where sensing inhibits pacing. This type of pacing mode is very seldom programmed today. Indeed, pacing during sensing is associated with an unnecessary increase in energy consumption with acceleration of battery wear. The triggered modes can be used in 2 special circumstances:
- in the event of detection of myopotentials or electromagnetic interference, a pacemaker programmed in SST mode does not inhibit but induces pacing on each artifact detected outside the refractory period, thus avoiding a pause in pacemaker-dependent patients. This type of mode was useful on older pacemaker models that were more sensitive to external interference since only functioning in unipolar mode.
- this mode enables evaluating sensing in the chamber under consideration as well as verifying that there is no crosstalk and that the extrasystoles are also properly sensed. In this tracing, for example, the AAT mode allows verifying that a) the sensing of sinus activity is correct, b) the sensing of the atrial extrasystoles is also correct, c) there is no far-field R wave oversensing.
