Multimodality Imaging-Guided Ventricular Tachycardia Ablation in a Hypoplastic Right Ventricle After Glenn Palliation

Adults with single-ventricle physiology increasingly survive into adulthood and may develop complex ventricular arrhythmias. A 44-year-old man with severe right ventricular hypoplasia and previous bidirectional Glenn palliation presented with sustained monomorphic ventricular tachycardia. Transthoracic and intracardiac echocardiography, computed tomography, and high-density electroanatomic mapping were combined to reconstruct the right-sided anatomy and to characterize the arrhythmogenic substrate. Intracardiac echocardiographic contours were merged with the electroanatomic map to build the geometry of the rudimentary right ventricle, in which extensive low-voltage areas were identified, with the latest and most fragmented late potentials confined to the anterior right ventricular outflow tract. Programmed stimulation did not induce ventricular tachycardia; however, pace mapping within the late-potential region reproduced the clinical QRS morphology with a stimulus-to-QRS interval of 153 milliseconds. Ablation was therefore guided by substrate homogenization, and a postablation high-density remap confirmed abolition of all late potentials. A subcutaneous implantable cardioverter-defibrillator was implanted before discharge.