Exercise-Induced Bidirectional Ventricular Tachycardia with Alternating Right and Left Bundle Branch Block-Type Patterns

Abstract

Exercise-induced ventricular tachycardia in young adults may occur with various structural heart diseases or with structurally normal heart. The structural heart diseases reported to cause exercise-induced ventricular tachycardia in this patient population include arrhythmo genic right ventricular dysplasia, hypertrophic cardiomyopathy, dilated cardiomyopathy, myocarditis, congenital heart disease, and myocardial ischemia. The conditions well identified to cause exercise-induced ventricular tachycardia with structurally normal heart are congen ital long-QT syndrome and familial polymorphic ventricular tachycardia. Exercise-induced ventricular tachycardia may display polymorphic, monomorphic, or bidirectional morphologies. A case of exercise-induced catecholamine-sensitive bidirectional ventricular tachycardia with alternating right and left bundle branch block patterns is reported in a young boy in the absence of structural heart disease, the conditions causing bidirectional ventricular tachy cardia, and family history of such an event or sudden cardiac death. The bidirectional tachy cardia typically displays right bundle branch block in right precordial leads with alternating polarity of the QRS-complex in frontal plane leads but in this case the bidirectional morphology of tachycardia was caused by alternating right and left bundle branch block-type patterns. The conditions causing bidirectional ventricular tachycardia are digoxin toxicity, ischemic heart disease, hypokalemia, myocarditis, and familial polymorphic ventricular tachycardia syndrome but the exact cause in this patient remained obscure, and the possibility of an underlying elec trical or ion channel disease of the heart could not be ruled out.