Cardiac resynchronization therapy-induced proarrhythmia: understanding preferential conduction within myocardial scars

Cardiac resynchronization therapy (CRT)–induced proarrhythmia is a clinically described entity, often included in the differential diagnosis for patients presenting with electrical storm, but rarely proven based on available data. Electrophysiologists consulting on patients with a CRT device in place often query the possibility of this entity. Yet, unless electrical storm immediately follows CRT implantation and the ventricular tachycardia (VT) morphology matches the left ventricular (LV) pacing morphology, the speculation is often short-lived.