RESUMEN
BACKGROUND: A 53-year-old male with heart failure secondary to anterior wall myocardial infarction treated with cardiac resynchronization-defibrillator (CRT-D) device presented with ventricular arrhythmia: repetitive incessant slow ventricular tachycardias (VT) below the CRT-D detection zone, accelerated ventricular rhythm, and numerous premature ventricular ectopic beats (ExV), resulting in loss of biventricular pacing. METHODS AND RESULTS: Nonsustained monomorphic VT (nsVT) and ExV were observed in an electrocardiogram under biventricular stimulation. During noninvasive CRT-D programming, ventricular bigeminy reproducibly recurred only at right ventricular (RV) pacing and its morphology was almost identical to the stimulated beats. The left ventricular (LV) pacing failed to induce ventricular ectopy or tachycardia. CONCLUSIONS: This unusual case shows a rare phenomenon of late proarrhythmic effect due to the RV lead pacing-a new finding reported only in a few publications. Here we present our approach to CRT programming that suppressed the clinical arrhythmia without the need of catheter ablation and achieving the high biventricular pacing capture rate along with optimal hemodynamic CRT-D performance.