Myocardial blood flow measured with thermoelectrical method and tissue oxygen tension in the ischemic heart models of cats: the influence of several drugs.

Abstract

Myocardial ischemic models were made by partial stenosis of the left anterior descending artery (LAD) with a compressing hydraulic balloon occluder or by complete occlusion of it by ligation in curarized cats under artificial respiration. Myocardial blood flow and tissue oxygen tension (PO2) in three different parts (ischemic center, margin, normal myocardium) were measured continuously with thermoelectrical and electrochemical methods. The three parts were distinguished by nitro blue tetrazolium (NBT) stain. The influences of the drugs given intravenously were tested using the model of complete occlusion. The drugs were 1 μg/kg adrenaline, 0.5 mg/kg papaverine, 20 μg/kg nitroglycerin, 100 μg/kg diltiazem and 1 mg/kg dipyridamole. When partial stenosis of LAD was made several times under different compressions, blood flow and P02 in the ischemic center decreased according to the grade of compression. Furthermore, the fall of PO2 was more pronounced than the decrease of blood flow. When LAD was completely occluded, the blood flow decreased to the level of 30-60 % of that before occlusion in the ischemic center and 70-85 % in the margin. In the normal myocardium, the blood flow increased slightly with the exception of a few cases. Then, PO2 fell to 3-5 mmHg in the ischemic center and to 8-15 mmHg in the margin from the level before occlusion (25-40). The effects of drugs after occlusion diminished markedly in the ischemic center and less markedly in the margin. Nitroglycerin was the most effective in preventing the decrease in blood flow by occlusion in the ischemic center. Dipyridamole and diltiazem raised P02 and reserved blood flow in the margin.