Use of a Novel Endoscopic Catheter for Direct Visualization and Ablation in an Ovine Model of Chronic Myocardial Infarction
Background—Defining the arrhythmogenic substrate is essential for successful ablation of scar-related ventricular tachycardia (VT). The visual characteristics of endocardial ischemic scar have not been described in vivo. The goal of this study was to 1) quantify the visual characteristics of normal tissue, scar border zone and dense scar in vivo using a novel endoscopic catheter that allows direct endocardial visualization and 2) correlate visual attributes of myocardial scar with bipolar voltage.
Methods and Results—Percutaneous transient balloon occlusion (150mins) of the mid-LAD coronary artery was performed in an ovine model. Animals were survived for 41.5±0.7 days. Detailed bipolar voltage maps of the left ventricle were acquired using NavX. Video snapshots of the endocardium were acquired at sites distributed throughout the left ventricle. Visual tissue characteristics of normal (>1.5mV), border (0.5-1.5mV) and dense scar (<0.5mV) were quantified using image processing. Radiofrequency (RF) lesions (10-20W, 30secs) were delivered under direct visualization. Mean white-threshold pixel area was lowest in normal tissue (189,969 ± 41,478pixels2), intermediate in scar border zone (255,979 ± 36,016pixels2) and highest in dense scar (324,452 ± 30,152pixels2, p<0.0001 for all pairwise comparisons). Tissue "whiteness", characteristic of scar, was inversely correlated with bipolar voltage (p<0.0001). During RF lesions, there was a significant increase in white-thresholded pixel area of the visual field after ablation (average increase 85,381 ± 52,618 pixels2; P<0.001).
Conclusions—Visual characteristics of chronic infarct scar in vivo using a novel endoscopic catheter correlate with bipolar electrogram voltage. Irrigated RF lesions in normal endocardial tissue and post-infarction zone can be visualized and quantified using image processing. This technology shows promise for visually based delivery of RF lesions for the treatment of scar-based VT.
- Received April 15, 2012.
- Accepted September 7, 2012.
- Copyright © 2012, American Heart Association, Inc. All rights reserved. Unauthorized use prohibited