Catheter Ablation of Ventricular Tachycardia Beneath an Endoventricular Patch

Abstract

A 70-year-old male with a history of ischemic heart disease with a left ventricular ejection fraction of 35% was referred for ablation to control recurrent episodes of ventricular tachycardia (VT) despite amiodarone therapy and a previous failed catheter ablation attempt. He had undergone coronary artery bypass grafting 20 years ago, and reoperation for mitral valve repair and endoventricular patch reconstruction (Dor procedure) of an anteroapical left ventricular aneurysm 10 years ago.After informed written consent was obtained, catheter mapping and ablation were performed with saline irrigated-tip catheter using electroanatomic mapping (CARTO; Biosense Webster, Diamond Bar, CA). A monomorphic VT with right bundle-branch block morphology in V1 was inducible and hemodynamically tolerated. Intracardiac echocardiography showed a pouch beneath the patch, consistent with dehiscence of a portion of the endoventricular patch, which had been recognized shortly after surgery 10 years previously (Figure 1). No thrombus was evident in the left ventricle (LV) or the pouch. Three-dimensional shells of the LV, the patch, and the apical aneurysmal pouch were separately created using intracardiac echocardiography ( Figure 2). During LV mapping the ablation catheter was observed to enter the LV pouch from a site on its lateral aspect. A site with late potentials during sinus rhythm and presystolic fractionated electrograms during VT was found at the septal aspect of the apical pouch. Entrainment of VT at this site showed minimal fusion and the postpacing interval assessment relative to the tachycardia cycle length, consistent with an area in an outer loop near the exit (Figure 3). VT terminated 4 seconds after initiation of radiofrequency current application at this site. Radiofrequency ablation was applied until pacing at 10-mA 2-ms pulse width no longer captured. After ablation, no sustained VT was inducible by programmed electric stimulation with up to 3 extrastimuli from the right ventricle and LV with or without isoproterenol infusion. The patient has remained free of VT during 1 year of follow-up.When VT occurs in the setting of an anterior LV aneurysm, simple resection of the aneurysm often fails to abolish VT, and resection or ablation that includes the surrounding scarred endocardium is usually effective.1 Surgical left ventricular reconstruction with an endovascular dacron or pericardial patch was described by Dor et al 2 as a method to preserve physiological geometry. It excludes access to the aneurysm and some of the infarct border zone, which may contain the substrate for VT. Ablation of VT can sometimes be achieved at sites along the border of the patch, but if this fails, a surgical approach to reach myocardium beneath the patch may be required.3 Percutaneous epicardial ablation is often not possible because of pericardial adhesions that limit pericardial access, and the VT may originate deep to the epicardium in any case. Transcoronary ethanol ablation could also be considered. 4 In this case, dehiscence of a po...