Radiofrequency Ablation of Recurrent Ventricular Premature Complex Originating from near Left Ventricular Summit Guided by Intracardiac Echocardiography

Outflow tracts are common sites of origin for ventricular tachycardia (VT) or a ventricular premature complex (VPC), especially in young patients without structural heart disease. Up to 90% of outflow tract VT is considered to originate from the right side, mainly from the right ventricular outflow tract (RVOT).1 Left ventricular outflow tract (LVOT) tachycardia can arise from any aspect of the heart, including endocardial or epicardial sites.2 The origin of idiopathic outflow tract VT can be closely related to important adjacent structures like the aortic valve leaflet and coronary artery; therefore, radiofrequency (RF) ablation can damage these structures without an understanding of the anatomical relationships.3,4 In this respect, intracardiac echocardiography (ICE) can improve the safety and efficacy of RF ablation by identifying anatomical details not visible by fluoroscopy and by confirming stable catheter placement and lesion formation at the target site.5,6


Introduction
Outflow tracts are common sites of origin for ventricular tachycardia (VT) or a ventricular premature complex (VPC), especially in young patients without structural heart disease. Up to 90% of outflow tract VT is considered to originate from the right side, mainly from the right ventricular outflow tract (RVOT). 1 Left ventricular outflow tract (LVOT) tachycardia can arise from any aspect of the heart, including endocardial or epicardial sites. 2 The origin of idiopathic outflow tract VT can be closely related to important adjacent structures like the aortic valve leaflet and coronary artery; therefore, radiofrequency (RF) ablation can damage these structures without an understanding of the anatomical relationships. 3,4 In this respect, intracardiac echocardiography (ICE) can improve the safety and efficacy of RF ablation by identifying anatomical details not visible by fluoroscopy and by confirming stable catheter placement and lesion formation at the target site. 5,6 Case A 40-year-old man referred to our hospital presented with palpitations and dyspnea. The patient had been followed-up for a year, with frequent monomorphic VPCs at a local clinic. He had no underlying medical conditions or structural heart disease at the time of diagnosis. Trans-thoracic echocardiography was follow-up 24-hour Holter monitoring. We considered the probability of VPCs originating from the LV summit, because a precordial pattern break was present, which showed a smaller R wave in lead V 2 than in V1 and V3, and maximum deflection index >55% in 12-lead ECG before the second procedure ( Figure 3).
The redo procedure was planned under the guidance of ICE.
Although the possibility of VPCs originating from the LV summit was apparent, we began mapping the outflow tract endocardium first based on the previous report showing successful ablation of LV summit VT from the opposite endocardial side in more than half of the cases. 7 We ablated the earliest activation site with a good pacemap in the RVOT anterior septum and confirmed stable contact of the catheter to the ablation site by ICE. Due to the occasional appearance of VPCs, we mapped the LVOT area additionally by trans-aortic approach. The earliest activation site was directly opposite to the RVOT ablation lesions.
During the application of RF energy (maximum 40W, 160 seconds), stable contact of the catheter was confirmed by ICE.
Lesion formation was also clearly visualized by ICE and the transmural lesion was identified ( Figure 4A and 4B). Unlike in the first ablation procedure, VPCs disappeared within a second of application of RF energy and no VPC appeared until discharge.
At the 1-month follow-up, the patient no longer complained of palpitations and no single VPC was seen on 12-lead ECG.

Discussion
Structurally, the outflow tracts are common sites for the origin of VT or VPC in the normal heart. 1,2 Although outflow tract VT prognosis is favorable, there is potential for VPC-related cardiomyopathy or even sudden cardiac arrest. 8,9 Catheter ablation is an effective therapeutic option as well as medical therapy such as An epicardial origin is suggested by ECG characteristics including a pseudo-delta wave ≥34 ms, pattern break in the precordial leads, and maximum deflection index ≥0.55. 11 Because of its proximity to major coronary arteries and fat tissue, a direct epicardial approach is usually limited. Therefore, if ablation within the coronary venous system is not feasible or safe, an attempt can be performed from the LV endocardium. If this approach is insufficient regarding effectiveness, ablation from the RVOT septum can be attempted with a longer application of RF energy with higher power. 12