Hyperspectral imaging for label-free in vivo identification of myocardial scars and sites of radiofrequency ablation lesions

Treatment of cardiac arrhythmias often involves ablating viable muscle tissue within or near islands of scarred myocardium. Yet, today there are limited means by which the boundaries of such scars can be visualized during surgery and distinguished from the sites of acute injury caused by radiofrequency (RF) ablation. We sought to explore a hyperspectral imaging (HSI) methodology to delineate and distinguish scar tissue from tissue injury caused by RF ablation. RF ablation of the ventricular surface of live rats that underwent thoracotomy was followed by a 2-month animal recovery period. During a second surgery, new RF lesions were placed next to the scarred tissue from the previous ablation procedure. The myocardial infarction model was used as an alternative way to create scar tissue. Excitation-emission matrices acquired from the sites of RF lesions, scar region, and the surrounding unablated tissue revealed multiple spectral changes. These findings justified HSI of the heart surface using illumination with 365 nm UV light while acquiring spectral images within the visible range. Autofluorescence-based HSI enabled to distinguish sites of RF lesions from scar or unablated myocardium in open-chest rats. A pilot version of a percutaneous HSI catheter was used to demonstrate the feasibility of RF lesion visualization in atrial tissue of live pigs. HSI based on changes in tissue autofluorescence is a highly effective tool for revealing—in vivo and with high spatial resolution—surface boundaries of myocardial scar and discriminating it from areas of acute necrosis caused by RF ablation.