Substrate Characterization and Catheter Ablation for Monomorphic Ventricular Tachycardia in Patients With Apical Hypertrophic Cardiomyopathy

UNLABELLED: VT Ablation in Apical Hypertrophic Cardiomyopathy. INTRODUCTION: Monomorphic ventricular tachycardia (VT) is uncommon in apical hypertrophic cardiomyopathy (HCM). The purpose of this study was to define the substrate and role of catheter ablation for VT in apical HCM. METHODS: Four patients with apical HCM and frequent, drug refractory VT (mean age of 46 ± 10 years, left ventricular LV ejection fraction; 54 ± 14%) underwent catheter ablation with the use of electroanatomic mapping. Endocardial mapping was performed in 4 patients and 3 patients underwent epicardial mapping. RESULTS: In 3 patients, VT was related to areas of scar in the apical LV where maximal apical wall thickness ranged from 14.5 to 17.8 mm, and 2 patients had apical aneurysms. Endocardial and epicardial substrate mapping revealed low voltage (<1.5 mV) scar in both endocardial and epicardial LV in 2 and only in the epicardium in 1 patient. Inducible VT was abolished with a combination of endocardial and epicardial ablation in 2 patients, but was ineffective in the third patient who had intramural reentry that required transcoronary ethanol ablation of an obtuse marginal vessel for abolition. The fourth patient had focal nonsustained repetitive VT from right ventricular outflow tract (RVOT), consistent with idiopathic RVOT-VT, that was successfully ablated. During follow-ups of 3-9 months, all patients remained free from VT. CONCLUSION: Monomorphic VT in apical HCM can be due to endocardial, epicardial or intramural reentry in areas of apical scar. Epicardial ablation or transcoronary alcohol ablation is required in some cases.