INNOVATIVE COLLECTIONS COMPLEX CASE STUDY Idiopathic Ventricular Tachycardia Originating from a Myocardial Extension into the Non- coronary Aortic Cusp: the Significance of Unipolar Electrograms STAVROS STAVRAKIS, MD, PhD, ADRIAN C. DUSA, MD, PAUL GARABELLI, MD and SUNNY S. PO, MD, PhD Heart Rhythm Institute, Section of Cardiovascular Diseases, University of Oklahoma Health Sciences Center, Oklahoma City, OK ABSTRACT. We present a 25-year-old woman with highly symptomatic premature ventricular complexes originating from a myocardial extension into the non-coronary aortic cusp and highlight the significance of unipolar electrograms in selecting the ablation target. KEYWORDS. ablation, unipolar electrogram, premature ventricular complexes. ISSN 2156-3977 (print) ISSN 2156-3993 (online) ’ 2013 Innovations in Cardiac Rhythm Management Introduction Ventricular tachycardia or premature ventricular com- plexes (PVCs) originating from the right ventricular outflow tract (RVOT) usually occur in patients without structural heart disease, and radiofrequency ablation is the treatment of choice for drug-refractory PVCs. 1,2 PVCs originating from the left ventricular outflow tract or aortic cusps have been previously described and often represent a challenge for ablation. 3 Moreover, ventricular tachycardia or PVCs originating from the non-coronary aortic cusp are extremely rare. Precise localization of the origin of these arrhythmias can be greatly facilitated by analyzing both bipolar and unipolar electrograms. Case report A 25-year-old woman was referred for catheter ablation to treat highly symptomatic frequent PVCs. PVCs were monomorphic with the morphology shown in Figure 1. PVCs constituted 27% of her ventricular beats on a Holter monitor. She did not tolerate metoprolol because of fatigue. Her past medical history was otherwise unremarkable. Electrophysiological study was performed without seda- tion or anesthesia to maximize the inducibility. Multipolar catheters were advanced to the His bundle, right ventricular apex, right atrial appendage, and coronary sinus. In addition, a 20-pole circular catheter (LASSO, Biosense Webster Inc., Diamond Bar, CA) was positioned at the RVOT through a long sheath. Both activation mapping and electroanatomical mapping (CARTO XP, Biosense Webster Inc.) of the RVOT were used to identify the origin of the PVCs. A 3.5 mm externally irrigated catheter (Navistar ThermoCool, Biosense Webster Inc.) was used for mapping. Activation mapping of PVCs in the right ventricle and pulmonary artery revealed that the site of earliest activation was located in the posterior aspect of the RVOT (60 ms earlier than the onset of QRS). However, close examination of the unipolar electrogram morphol- ogy revealed that the initial electrogram deflection (15– 20 ms) represented a far-field component (Figure 2). In addition, multiple sites in the RVOT showed the same earliest activation timing, but the unipolar electrograms consistently demonstrated an initial far-field component of 15–20 ms (Figure 3). These findings indicated that the The authors report no conflicts of interest for the published content. Manuscript received August 1, 2013, Final version accepted August 21, 2013. Address correspondence to: Sunny S. Po, Heart Rhythm Institute, University of Oklahoma Health Sciences Center, 1200 Everett Dr, TCH 6E103, Oklahoma City, OK 73104. E-mail: sunny-po@ouhsc. edu The Journal of Innovations in Cardiac Rhythm Management, 4 (2013), 1407–1411 1407 The Journal of Innovations in Cardiac Rhythm Management, October 2013 DOI: 10.19102/icrm.2013.041004