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The effect of gradual coronary artery occlusion on in vitro platelet aggregation as well as the “in vitro” platelet aggregate ratio of Wu and Hoak and was studied serially in a dog model. Healthy male adult mongrel dogs were subjected to thoracotomy. The circumflex artery was isolated and an Ameroid constrictor applied. This device consists of hygroscopic material which swells and occludes the artery gradually over a 14 day period (Circ. Res.40:384 1977.)Ten dogs were followed for 90 days. Platelet aggregation with ADP (10-3,10-5 and 10-6M) as well as the platelet aggregate ratio (normal=0.8-1.0) were determined preoperatively and postoperatively at 7,14,30 and 90 days,respectively. After blood was obtained on day 90 the dog was anesthetized. The beating heart was removed and transferred to an isolated heart perfusion system. The 3 coronary vessels were cannulated and flow to each vessel was measured simultaneously under constant pressure perfusion. Collateral flow was assessed by the retrograde flow method. At the termination of the study hearts were perfused with buffered formaldehyde-gluteraldehyde. Cross-sectional slices were obtained and stained with Mallory stain. The infarct size was measured relative to the left ventricle size. There was a strong correlation (r= -0.8683) between the infarct size and platelet aggregate ratio at day 14, the time of total occlusion. This data relates decreased aggregate ratio (reflecting an increase in circulating platelet aggregates) to increased infarct size. There was also a correlation between platelet aggregation(10-3M ADP) preoperatively and at day 14 (r = 0.7508). The sensitivity of platelets to ADP (10-5M) increased significantly at 90 days (p |
