Ubiquitous Myocardial Extensions into the Pulmonary Artery Demonstrated by Integrated Intracardiac Echocardiography and Electroanatomic Mapping: Changing the Paradigm of Idiopathic Right Ventricular Outflow Tract Arrhythmias
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 (ICE) 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 pulmonic valve 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 the free wall side for both control patients (5.6 mm [IQR 3.6 - 7.7] vs 1.7 mm [IQR (-) 0.1 - (+) 4.0], p=0.002) and RVOT arrhythmia patients (5.7 mm [IQR 2.7 - 7.7] vs 1.4 mm [IQR (-) 0.8 - (+) 4.8], p=0.004). Eleven (46%) RVOT arrhythmia foci were localized beyond the valve in the pulmonary artery (median 8.2 mm above PV, IQR 6.6-10.3 mm); these locations were confirmed as supravalvular by direct ICE visualization.
Conclusions—Myocardial voltage extension into the pulmonary artery in humans is ubiquitous and can be demonstrated in vivo using 3D-integrated ICE to localize the pulmonic valve. These extensions frequently serve as origins of presumed RVOT arrhythmias; ICE localization of the pulmonic valve allows reclassification of these as pulmonary arterial arrhythmias.
- ventricular arrhythmia
- intracardiac echocardiography
- electrophysiology mapping
- pulmonary valve
- pulmonary artery
- Received September 6, 2013.
- Revision received April 18, 2014.
- Accepted May 11, 2014.