Quantitation of early myocardial ischemia using acridine orange fluorescence--an experimental study

It has been observed in the present investigation that ischemic myocardium consistently produces bright green fluorescence after Acridine Orange (AO) staining. The area of ischemia in the left ventricular myocardium at different time intervals after onset of experimental ischemia has been calculated by use of this AO fluorescence technique. Zonal distribution of ischemia in the epicardial, middle, and endocardial zones has also been evaluated quantitatively from ten minutes to six hours after ligation of the anterior descending branch of the left coronary artery in the Wistar strain of albino rats. No similar study was available for comparison from the literature reviewed. The total area of left ventricular ischemia showed an increase with the prolongation of duration of coronary ligation from 13.39 +/- 2.69 mm2 at ten to twenty-five minutes to 32.99 +/- 5.69 mm2 at six hours after ligation. Statistical analysis of the zonal area of ischemia has shown that ischemia in the middle and endocardial zones was greater than that in the epicardial zone at all time intervals recorded. Middle zone ischemia extended over a larger area than that over the endocardial zone at all intervals except at intervals II (30-45 min), IV (2-2 1/2 hrs) and V (3-4 hrs). The results of this experimental investigation are significant for these point to the value of Acridine Orange fluorescence in detecting early myocardial ischemia and in demarcating zonal differences in ischemia. The authors have successfully utilized the method in a few human cases of clinically suspected myocardial infarction and recommend the technique for routine use to detect early human myocardial ischemia.