Spectral Changes Caused By Radiofrequency Ablation Of Cardiac Tissue

New diagnostic catheters can be developed by delivering and acquiring light through a small fiberoptic bundle. This can provide a useful real time feedback guidance to observe tissue damage caused by thermal injury used to treat cardiac arrhythmias. Yet, little is known about the exact spectral changes caused by radiofrequency ablation (RFA) in different types of cardiac tissue. We hypothesized that the most sensitive optical ranges for characterizing thermal injury can be revealed by comparing spectral information from different areas of the heart before and after RF ablation. Freshly excised porcine hearts were used to acquire and analyze excitation emission matrices (EEMs, 300-600nm with 10 nm spectral step) from ventricular muscle, left atrial endocardium, and aorta. Each type of tissue exhibited distinct EEMs that underwent reproducible changes in fluorescence and reflectance upon RF ablation. Specifically, RFA resulted in a reduction of the NADH fluorescence peak in ventricular and atrial muscle EEMs (360/460nm excitation/emission maxima). It also led to a broadening of collagen fluorescence peak in the aorta and in left atrial tissue. RFA caused an increase in diffuse reflectance (seen as widening of the EEM diagonal line) in all three tissue types. Thermal coagulation of heme-containing proteins, including different forms of myoglobin, led to a weaker absorption in the Soret band range (410-430nm). The latter was particularly noticeable in ventricular tissue but was also significant in the left atrial tissue. We conclude that EEMs provide a wealth of quantitative information that can guide the development of new optical probes to monitor tissue injury and the degree of thermal damage caused by RF ablation of different parts of the heart. Supported by the NIH R41 HL120511 and the LuxCath-GWU Research Agreement.