Fluorescein Detection of Myocardial Ischemia in an Experimental Model of Acute Coronary Occlusion

Abstract

The objective was to evaluate the feasibility and sensitivity of fluorescein to determine and delineate an ischemic area in an experimental model of acute coronary occlusion. The studies were performed at the center for experimental Surgery at Hospital de Clínicas “Jose de San Martin.” All animal protocols were approved by the Institutional Animal Care and Use Committee (IACUC) at University of Buenos Aires. All animals were maintained in a pathogen-free environment throughout the experiments. We used ten New Zeeland rabbits. They served as their own control model. All the experiments were performed under general anesthesia with tracheostomy. Median sternotomy was performed and the second diagonal artery was ligated. The infracted area was evaluated under xenon and UV (530 nm) light after the administration of 0.01 mg/kg fluorescein Fluorescein 10 % was intravenously administrated. Electrocardiogram (EKG), pulse oximetry, heart rate (HR), Troponin, CPK, CPK-MB, and LDH were determined postoperatively. All the animals were euthanized at the end of the experiment and the heart was harvested for histopathologic examination. Biochemical (enzymatic) and electrocardiography analyses were performed at baseline and at 90 min after complete occlusion of the second diagonal artery: Baseline (BL) and post-ischemic (PI) measurements were performed for LDH, CPK, CPK-MB, and Troponin. ST segment elevation of 1.8 ± 0.65 mm was detected in every case after coronary artery occlusion. Oxygen saturation and heart rate were 97 ± 2 % and 145 ± 5 % respectively. Enzymes results are: LDH (BL) 159.7 ± 112.2 (U/L) vs LDH (PI) 1,012 ± 359.9 (U/L) (p < 0.001). CPK (BL) 1,072 ± 121.7 (U/L) vs. CPK (PI) vs. 359.5 ± 95.7 (U/L) (p < 0.001), CPK-MB (BL) 0.89 ± 0.42 (ng/ml) vs CPK-MB (PI) vs. 3.89 ± 1.9 (ng/ml) (p < 0.001), Troponin (BL) 0.06 ± 0.06 (ng/ml) vs. Troponin (PI) 19.6 ± 5.9 (ng/ml) (p < 0.001). The xenon light failed to demonstrate any changes in the ischemic area. However, when evaluated under the UV (530 nm wave length) light, a clearly demarcated area lacking fluorescence can be appreciated. The area represented 0.7225 ± 0.39 cm² in the anterior aspect of the myocardium distal to the ligated vessel. This was correlated and confirmed by microscopic evaluation. This study serves as a proof of principle that fluorescein detection of myocardial ischemia in an experimental model of acute coronary occlusion is feasible, sensitive, and reproducible. However, further clinical studies are required to understand if the findings of our study could be extrapolated into human studies.