Online Detection of Myocardial Ischemia by Near Infrared Spectroscopy with a Fiberoptic Catheter

The interruption of myocardial O2-supply in acute myocardial ischemia causes differences in coronary venous O2-content. In this study, the oxygenation status of coronary sinus blood is detected in myocardial ischemia by near infrared (NIR) spectroscopy. For the intravascular application, a new fiberoptic catheter is developed. After calibration of the catheter by perfusion of blood with standardized gas mixtures in an in vitro experiment, the in vivo application was performed in 12 domestic pigs. The catheter was placed into coronary sinus and an anterior ischemia was induced by temporary occlusion of LAD. NIR graphs and hemodynamic data were obtained for 90 min ischemia and 90 min reperfusion time. Main NIR-spectroscopic differences between oxygenated and de-oxygenated hemoglobin took place in O2-concentrations less than 30%. Coronary sinus NIR spectra of hemoglobin-oxygen binding showed significant, reproducible differences between pre-ischemia, LAD-occlusion and reperfusion. NIR graphs also show variations related to CO2-concentration, pH and temperature. The intravascular application of NIR spectroscopy could be a reliable tool in detection and follow-up of acute myocardial ischemia and infarction.