This 70-year-old man suffering from severe ischemic dilated cardiomyopathy with left bundle branch block received a Medtronic Viva XT CRT-D triple chamber defibrillator. Although he had readily responded to CRT, the system, first implanted on the left then on the right side, had to be entirely removed after two episodes of endocarditis. A pulse generator was surgically re-implanted with 2 coils, and bipolar atrial, RV and LV leads. He underwent routine follow-up.
Loss of RV captures due to dislodgement or rise in the pacing threshold of an actively fixated endocardial lead is uncommon. In this patient, however, both electrodes of the RV lead were surgically sewn onto the epicardium, relatively far from each other, explaining both the rise in threshold (epicardial are often higher than endocardial thresholds) and the double morphology of QRS. The capture threshold is usually high immediately after the surgical epicardial implantation of 4968 lead models, then decreases over the next 3 months, an evolution facilitated by the elution of steroids.
The loss of RV capture results in LV capture only, without changes in the refractory periods and without adaptation of the post-ventricular pacing ventricular blanking period. Pure LV stimulation is often associated with a wider QRS and double counting of the paced QRS sensed by the RV lead.
