MECHANISMS OF SUSTAINED VENTRICULAR-TACHYCARDIA IN MYOTONIC-DYSTROPHY- IMPLICATIONS FOR CATHETER ABLATION

Background-Ventricular arrhythmias have been documented and linked to the high incidence of sudden death seen in patients with myotonic dyst rophy. However, their precise mechanism is unknown, and their definiti ve therapy remains to be established. Methods and Results-We studied 6 consecutive patients with myotonic dystrophy and sustained ventricula r tachycardia by means of cardiac electrophysiological testing. Partic ular attention was paid to establish whether bundle-branch reentry was the tachycardia mechanism, and when such was the case, radiofrequency catheter ablation of either the right or left bundle branch was perfo rmed. Clinical tachycardia was inducible in all patients and had a bun dle-branch reentrant mechanism. In 1 patient, 2 other morphologies of sustained tachycardia were also inducible, neither of which had ever b een clinically documented, and both had a bundle-branch reentrant mech anism, Ventricular tachycardia was no longer inducible after bundle-br anch ablation, except for a nonclinically documented and nonsustained ventricular tachycardia in the only patient who had apparent structura l heart disease. Conclusions-A high clinical suspicion of bundle-branc h reentrant tachycardia is justified in patients with myotonic dystrop hy who exhibit wide QRS complex tachycardia or tachycardia-related sym ptoms. Because catheter ablation will easily and effectively abolish b undle-branch reentrant tachycardia, myotonic dystrophy should always b e considered in patients with sustained ventricular tachycardia. This is especially true if no apparent heart disease is found.