Idiopathic monomorphic ventricular tachycardia originating from the left aortic sinus cusp in children: endocardial mapping and radiofrequency catheter ablation

Background: Idiopathic repetitive monomorphic ventricular tachycardia with an inferior axis and left bundle branch block pattern typically originates from the superior right ventricular outflow tract. When indicated, radiofrequency catheter ablation is usually safe and effective. However, a left ventricular origin has been described recently in adult patients in whom ablation attempts in the right ventricular outflow tract were unsuccessful. Experience in pediatric patients is limited. Patients and Methods: Since 1998, 13 young patients suffering from symptomatic ventricular tachycardia episodes with an inferior axis and left bundle branch block pattern underwent an electrophysiological study and radiofrequency catheter ablation. In 2 patients, age 13 and 15 years, no endocardial local electrograms preceding the surface ECG QRS complex could be recorded within the right ventricular outflow tract during ventricular ectopy. Detailed mapping within the left ventricular outflow tract and in the aortic root revealed local electrograms 25 and 53 ms earlier than the QRS complex and a 11/12 and 12/12 lead match during pacing inferior and anterior to the ostium of the left main coronary artery in the left aortic sinus cusp. Earliest activation was recorded 10 and 12 mm away from the coronary artery ostium identified angiographically. In each of the patients, one single radiofrequency current application (60°C, 30 W, duration 30 and 60s, respectively) resulted in complete cessation of ventricular ectopy. Subsequent selective injection into the left coronary artery did not reveal any abnormalities. During follow-up (2 and 34months) off any antiarrhythmic drugs, both of the patients are in continuous normal sinus rhythm. Conclusion: In young patients with symptomatic idiopathic ventricular tachycardia originating from the left aortic sinus cusp, radiofrequency catheter ablation was safe and effective.