Persistent atrial fibrillation is commonly treated using an endoscopic catheter to eliminate anomalous sources of cardiac activity via thermal ablation. However, the procedure lacks real-time feedback. Newly developed radiofrequency ablation (RFA) catheters include a fiberoptic bundle through which visual information of tissue conditions may be collected offering an opportunity to reveal subtle differences in tissue physiology. Currently little is known about the spectral changes caused by RFA. We hypothesized that by comparing spectral changes in various areas in the heart before and after RFA, optical signatures can be used to distinguish healthy cardiac tissue from thermally ablated tissue. Excitation emission matrices (EEM) were acquired from excised porcine hearts (300-600nm). Distinct EEMs were collected from the endocardium of the left atria, ventricle, and aorta. Additionally, the fluorescence and reflectance profiles of each tissue were altered by thermal ablation. In the ventricular muscle, a reduction in the NADH fluorescence peak (360/460nm excitation/emission maxima) was most prominent. While in the aorta, collagen and elastin fluorescence peaks fused and broadened upon ablation. Changes in atrial tissue included a drop in NADH fluorescence and an overall increase in reflectance. The latter is likely caused by thermal coagulation of heme-containing proteins such as myoglobin and a weaker absorption within the Soret band. We concluded that optical signals revealed by EEMs offer quantitative information that can be used to develop diagnostic catheters, including hyperspectral imaging protocols to discern spectral changes elicited by RFA treatment.
Radiofrequency ablation combined with conductive fluid-based dopants (saline normal and colloidal gold): Computer modeling and ex vivo experiments.
