Proarrhythmic effect of bipolar epicardial left ventricular stimulation in CRT, resolved maintaing biventricular pacing with unipolar-cathodical configuration: a peculiar case report

Background: The effect of cardiac resynchronization therapy (CRT) on the risk of ventricular arrhythmias is controversial. Several studies reported a decreased risk, but some studies reported a potential proarrhythmic effect of epicardial left ventricular pacing resolved upon discontinuation of biventricular pacing (BiVp). Case Summary: A 67-years old woman with a history of heart failure due to non-ischemic cardiomyopathy and left bundle brunch block was hospitalized for CRT device implantation. Unpredictably, as soon as the leads have been connected to the generator, electrical storm (ES) occurred with relapsing self-resolving polymorphic ventricular tachycardia (PVT) triggered by ventricular extra beats with short-long-short sequence. The ES was resolved without interrupting BiVp switching to unipolar left ventricular (LV) pacing. This allowed to keep CRT active with extreme clinical benefit for the patient and to demonstrate that the cause of the PVT was the anodic capture of bipolar LV stimulation. Reverse electrical remodeling was also demonstrated after 3 months of effective BiVp. Discussion: Proarrhythmic effect of CRT is a rare but significant complication of CRT, and it may compel to discontinue the BiVp. The reversal of the physiological transmural activation sequence of epicardial LV pacing and subsequent prolonging of corrected QT interval have been speculated as the most probable explanation, but our case highlights the possibility that the anodic capture may play a relevant role in PVT genesis.