Assessing epicardial substrate using intracardiac echocardiography during VT ablation

Background-Intracardiac echocardiography (ICE) has played a limited role in defining the substrate for ventricular tachycardia (VT). The purpose of this study was to assess whether ICE could identify abnormal epicardial substrate in patients with nonischemic cardiomyopathy (NICM) and VT. Methods and Results-We studied 18 patients with NICM and recurrent VT who had abnormal echogenicity identified on ICE imaging. Detailed left ventricular (LV) endocardial and epicardial electroanatomic mapping was performed in all patients. Low-voltage areas (<1.0 mV) in the epicardium were analyzed. ICE imaging in the NICM group was compared to a control group of 30 patients with structurally normal hearts who underwent ICE imaging for other ablation procedures. In 18 patients (age, 53±13 years; 17 men) with NICM (ejection fraction, 37±13%), increased echogenicity was identified in the lateral LV by ICE imaging. LV endocardial electroanatomic mapping identified normal voltage in 9 patients and at least 1 confluent low-voltage area (6.6 cm ²; minimum-maximum, 2.1-31.7 cm ²) in 9 patients (5 posterolateral LV, 4 perivalvular LV). Detailed epicardial mapping revealed areas of low voltage (39 cm ²; minimum-maximum, 18.5-96.3 cm ²) and abnormal, fractionated electrograms in all 18 patients (15 posterolateral LV, 3 lateral LV). In all patients, the epicardial scar identified by electroanatomic mapping correlated with the echogenic area identified on ICE imaging. ICE imaging identified no areas of increased echogenicity in the control group. Conclusions-ICE imaging identified increased echogenicity in the lateral wall of the LV that correlated to abnormal epicardial substrate. These findings suggest that ICE imaging may be useful to identify epicardial substrate in NICM.