Dislodgement of atrial lead

Patient

A 78-year-old man received an Adapta dual chamber pacemaker for complete AV block; this tracing was recorded on the morning after the day of device implantation.

Trace

The first channel is lead II of the surface ECG with the event markers superimposed, the second is lead III with the time intervals superimposed and the third is lead I;

non-sensed atrial event;
atrial pacing at the end of the escape cycle; the QRS begins after this “atrial” pacing; the atrial lead, in fact, paced the ventricle. The paced ventricle is sensed by the ventricular channel (VS) in the post-atrial pacing safety window. The ventricular channel then delivers a ventricular stimulus (VP) at the end of the safety window, falling in the natural ventricular absolute refractory period;
repetition of the AP-VS-VP cycles.

Comments

In this patient, the chest x-ray showed a dislodgement of the atrial lead, with its extremity in the ventricle, explaining the observations made on this tracing, which are similar to what is observed when the atrial and ventricular leads have been inadvertently switched, showing a double spike, with the first spike capturing the ventricle. Unlike on this tracing, however, the second spike usually occurs at the end of the AV delay and is followed by an atrial depolarization.

Pacing & Defibrillation

ECG

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