Exercise-induced ventricular tachycardia in a case with hypertrophic cardiomyopathy taking cibenzoline.

We report a 17-year-old woman with hypertrophic cardiomyopathy (HCM) successfully resuscitated from ventricular fibrillation while taking cibenzoline. During exercise-stress testing before implanting an implantable cardioverter-defibrillator, ventricular tachycardia was induced and thought to be a proarrhythmia due to the use-dependent effect of the Na channel blockade with cibenzoline. In patients with arrhythmogenic substrates such as HCM, it is critical to pay attention to the proarrhythmic effects of class I antiarrhythmic drugs while increasing heart rate.