Rapid and Potent Antiarrhythmic Effect of Cardiac Resynchronization Therapy in a Patient with Advanced Dilated Cardiomyopathy and a Large Ventricular Arrhythmia Burden.

We report a case demonstrating a rapid and potent antiarrhythmic effect of biventricular pacing. A 67-year-old male patient with dilated cardiomyopathy was admitted for heart failure. The initial surface electrocardiogram revealed a left bundle branch block with a QRS complex duration of 200 ms. Echocardiographic examination revealed a left ventricular ejection fraction of 16%, a left ventricular end-diastolic dimension of 91 mm, and marked interventricular dyssynchrony. Continuous rhythm monitoring revealed frequently-recurring non-sustained monomorphic ventricular tachycardia (VT). Polymorphic VT, which persisted for 27 seconds, occurred on the third day after admission, and the R on T phenomenon recurred every two to three days thereafter. Optimal medical therapy for four weeks failed to suppress the recurrence of ventricular arrhythmias or ameliorate heart failure. Cardiac resynchronization therapy was initiated for an anticipated antiarrhythmic effect of biventricular pacing. Three days after the initiation of biventricular pacing, the ventricular arrhythmias disappeared almost completely.