We report a three month old infant who developed a persistent junctional reciprocating tachycardia induced cardiomyopathy that was successfully treated with radiofrequency ablation. To our knowledge this is the youngest reported patient with a successful epicardial lesion placed in a diverticulum off of the coronary sinus. We use this case to highlight how low power lesions in the coronary sinus in the youngest of patients can achieve results safely. Delineation of coronary anatomy is crucial prior to lesion deliverance.