An electrophysiologic study of a child with idiopathic sustained left ventricular tachycardia.

A child with congestive heart failure was found to have a paroxysmal ventricular tachycardia (VT) without structural heart disease. This wide QRS tachycardia had an atrioventricular dissociation and a QRS pattern of right bundle branch block and left axis deviation. The tachycardia did not respond to lidocaine or procainamide but instantly responded to verapamil therapy. This VT could be initiated or terminated by either atrial or ventricular pacing during electrophysiologic study. The endocardial biopsy showed that there was myocardial hypertrophy with mild degree of interstitial fibrosis. This entity of ventricular tachycardia often occurs in young people with no overt heart disease but with subclinical endomyocardial changes.