Fluorescent cardiac Imaging - A novel Intraoperative method for quantitative assessment of myocardial perfusion during graded coronary artery stenosis

Background-The purpose of the present study was to examine whether the effect of coronary stenoses of variable severity on myocardial perfusion can be quantitatively assessed in vivo by analysis of fluorescent cardiac imaging (FCI) compared with the gold standard, the fluorescent microsphere method. FCI is a novel technology to visualize coronary vessels and myocardial perfusion intraoperatively using the indocyanine green dye with an infrared-sensitive imaging device. Methods and Results-Graded stenoses and total vessel occlusion of the left anterior descending coronary artery were created in 11 open-chest pigs. Stenoses were graded to reduce resting left anterior descending coronary artery flow by 25%, 50%, 75%, and 100% of baseline flow measured by transit-time flowmeter. FCI images were analyzed with a digital image processing system. The impairment of myocardial perfusion was quantified by background-subtracted peak fluorescence intensity and slope of fluorescence intensity obtained with FCI and compared with myocardial blood flow assessed by fluorescent microsphere. All stenoses resulted in an impairment of myocardial perfusion visualized by FCI. Occlusion of the left anterior descending coronary artery resulted in a total perfusion defect ( no fluorescence intensity) of the corresponding anterior myocardial wall. During graded stenosis and total vessel occlusion, normalized background-subtracted peak fluorescence intensity and slope of fluorescence intensity decreased significantly (P < 0.0001). Both background-subtracted peak fluorescence intensity (r=0.92, P < 0.0001) and slope of fluorescence intensity (r=0.93, P < 0.0001) analyzed by FCI demonstrated good linear correlation with fluorescent microsphere derived myocardial blood flow. Conclusions-The impairment of myocardial perfusion in response to increased coronary stenosis severity and total vessel occlusion can be quantitatively assessed by FCI and correlates well with results obtained by fluorescent microsphere.