Ubiquitous Myocardial Extensions Into the Pulmonary Artery Demonstrated by Integrated Intracardiac Echocardiography and Electroanatomic Mapping

Abstract

Background—Idiopathic ventricular arrhythmias of left bundle branch block inferior axis morphology are usually localized to the right ventricular outflow tract (RVOT), presumably below the pulmonic valve (PV). However, the PV location is usually not confirmed by direct visualization. Methods and Results—Intracardiac echocardiography was used to visualize and tag the PV annulus, which was then integrated with 3-dimensional voltage maps of the RVOT. Distances were measured from the furthest extent of myocardial signal (bipolar voltage ≥1.5 mV) to the PV annulus. This was performed in 24 control patients and 24 prospective patients with RVOT arrhythmias. Myocardial signal beyond the PV was found in 92% of controls and 88% of RVOT arrhythmia patients (P=1.000). Average myocardial extension was further on the septal side than on the free wall side for control patients (5.6 mm; interquartile range [IQR], 3.6–7.7, versus 1.7 mm; IQR (−)0.1 to (+)4.0; P=0.002) and RVOT arrhythmia patients (5.7 mm; IQR, 2.7–7.7, v...