Visualization of cryolesions in blood-free and blood-perfused preparations. A. Saline-perfused excised rat heart under incandescent room light and under 365nm illumination/475nm acquisition settings. Intensity profiles across dotted while lines for both images are shown in the right. Scale bar 2 mm. B. Color snapshot of cryoablated epicardial surface as seen in an open-chest animal under incandescent illumination. The same heart under 365/475nm settings showing two lesions: one ventral and one apical. Dot plot on the right compares % change in signal intensity under the two acquisition settings (n=7, p<0.05, scale bar 2 mm) C. When the ablated heart was immersed into a blood-filled beaker, the blood blocked the fNADH signal. However, displacement of blood using a transparent film enabled fNADH-based lesion visualization, pointing to the need for a transparent inflatable balloon to be included in future designs of fNADH imaging catheter.