Abstract 14828: Voltage and Echo Mapping of Ventricular Tachycardia from Right Ventricular Outflow Tract: Common Myocardial Extensions Beyond the Pulmonic Valve as Sites of Origin
Introduction Idiopathic ventricular tachycardia (VT) is commonly ablated in the RV outflow tract (RVOT). Electrogram amplitude is typically used to define the pulmonic valve (PV) plane, but this assumes myocardial tissue terminates at the valve. Intracardiac echo (ICE) can directly visualize the PV annulus.
Methods In 13 patients with structurally normal heart undergoing catheter ablation of RVOT VT, voltage maps of the RVOT were created in sinus rhythm using a 3.5-4mm tip catheter and CARTO (Biosense). Separate (blinded) anatomic points around the PV annulus were collected by Cartosound ICE; all points were ECG-gated. The two maps for each patient were superimposed and distances measured from the ICE-defined annulus to the most distal contact point with bipolar voltage ≥1.5 mV (indicating myocardial signal). For analysis, the PV plane was divided into 6 segments: septal-anterior, -mid, -posterior; free wall (FW)-anterior, -mid, -posterior.
Results Voltage maps were created with 82 ±80 points in RVOT; ICE PV planes were defined with 29 ±6 annular points. The mean ± std dev distance from distal point of ≥1.5mV to PV plane were: 3.6 ±4.8 mm beyond PV in septal anterior; 4.4 ±4.5 mm beyond in septal mid; 4.1 ±3.7 mm beyond in septal posterior; 2.3 ±4.8 mm beyond in FW anterior; 0.5 ±5.8 mm beyond PV in FW mid; 2.1 ±6.2 mm beyond in FW posterior. The septal side showed further extension beyond the valve than the FW side (4.0 ±4.2 mm vs. 1.6 ±5.5 mm; p=0.01). Twelve of 13 patients had at least 1 extension beyond the ICE-defined PV. The site of successful VT ablation was beyond the PV in 4 of 13 patients (mean 9.6 ±2.6 mm), all with voltage ≥ 1.5 mV at the ablation site (Figure).
Conclusions Frequently there is myocardial signal above the anatomic PV, consistent with myocardial extension beyond the pulmonic valve. This extension is more prominent on the septal side. Idiopathic RVOT VT may originate beyond the PV more often than is commonly appreciated but is under-recognized without the use of ICE.
- © 2012 by American Heart Association, Inc.