In vivo detection of myocardial ischemia in pigs using visible light spectroscopy.

Background: Monitoring tissue oxygenation (StO(2)) by visible light spectroscopy (VLS) can identify tissue ischemia, but its feasibility for detecting myocardial ischemia is not known. We hypothesized that VLS can reliably detect changes in myocardial StO(2) in pigs subjected to acute regional or global myocardial ischemia.

Methods: In 11 pigs, regional myocardial ischemia was created by ligation of left anterior descending artery (LAD). Myocardial StO(2) was determined from the ischemic and nonischemic left ventricular (LV) regions and compared to coronary venous saturations. Myocardial function was assessed by echocardiography. In six pigs, LV-StO(2) was measured during cardiopulmonary bypass (CPB), after cardioplegic cardiac arrest, and during CPB with inadequate myocardial protection. Additionally, right ventricular (RV)- and LV-StO(2) were assessed during acute RV pressure overload from pulmonary artery (PA) banding.

Results: StO(2) baselines in pigs undergoing LAD occlusion were similar in the ischemic and nonischemic myocardium (70% +/- 8% vs 74% +/- 5%). After LAD ligation, StO(2) rapidly declined (30 s: 59% +/- 8%; 1 min:50 +/- 9; 5 min:42% +/- 4%; P < 0.05) in the ischemic myocardium. Decreases in StO(2) correlated with coronary venous saturations (r = 0.88) and were associated with myocardial dysfunction. In pigs undergoing CPB, LV-StO(2) remained unchanged with initiation of CPB or after cardioplegic cardiac arrest, but LV ischemia was detected by StO(2) after aortic cross-clamp without adequate myocardial protection. Similarly, PA banding resulted in a profound decrease of RV-StO(2) from 69% +/- 6% to 52% +/- 7% (P < 0.05) with recovery after PA release.

Conclusions: VLS is a reliable method of detecting alterations in myocardial StO(2) and can be a useful monitor for rapid identification of myocardial ischemia.