Multiparameter Fiber Optic Sensor for the Assessment of Intramyocardial Perfusion

Objectives: The objective of this study was to characterize a multiparameter fiber optic sensor for detection of changes in intramyocardial perfusion and to demonstrate a method of determining critical values for pH, PCO2, and PO2 to indicate onset of anaerobic metabolism. Methods: Six swine underwent a 20‐minute occlusion of the left anterior descending coronary artery (LAD). Myocardial pH, PCO2, and PO2 were measured continuously in the LAD and left circumflex coronary artery (CFX) territories. Critical values for each parameter were calculated from these data. Results: During occlusion LAD myocardial pH declined from 7.36 ± 0.04 to 6.85 ± 0.04; PCO2 rose from 57.0 ± 2.9 to 154.0 ± 18.0 torr, PO2 fell from 78 ± 20 to 6 ± 5 torr. No myocardial pH or PCO2 changes were observed in the CFX region, however, CFX PO2 was affected in some animals during LAD occlusion and release. Methods for determining the ischemic threshold from these sensor data are presented. Conclusions: Multiparameter fiber optic sensors reliably respond to coronary occlusion and thus have the potential to help guide myocardial protection strategies for both on‐ and off‐pump cardiac surgery. (J Card Surg 2004;19:167‐174)