The percentage of the ischemic risk zone infarcting following permanent coronary occlusion is independent of ischemic zone size.
The relationship between the amount of myocardium rendered ischemic, the risk zone, and the percentage of that zone which ultimately infarcts (% I/R) was examined in the closed chest canine model. Twenty-three dogs were anesthetized with pentobarbital. A special cannula was inserted through a carotid artery into the left coronary ostium. A teflon bead was infused through the cannula, thus, embolizing a distal coronary branch. Two to 8 minutes after the coronary embolization, 20 million radiomicrospheres labeled with 141Ce (15 mu in diameter) were injected into the left ventricle. This allowed the collateral blood flow in the risk zone to be measured and defined the ischemic zone. The dogs were sacrificed either 24 or 48 hours after coronary occlusion and the hearts were excised and sectioned into 5 mm thick slices. The risk zones were visualized by microsphere autoradiography while the infarcts were visualized by triphenyl tetrazolium staining. The volumes of both zones were determined by planimetry. Experiments were retrospectively divided into either a small risk zone group (risk zones smaller than 18% of the ventricle, n = 13) or a large risk zone group (risk zones larger than 18% of the ventricle, n = 10). There was a very close correlation between the % I/R and collateral blood flow in both the small and the large risk zone groups (Y = 90.85-1.07X, r = -0.88 vs Y = 88.84-0.91X, r = -0.93). That correlation was not statistically different between the 2 groups. These findings indicate that risk zone size itself does not influence the percentage of the risk zone which is infarcted in this model.
Miura
T
T
Department of Physiology, College of Medicine, University of South Alabama.
Downey
J M
JM
D000818:Animals; D002306:Cardiac Volume; D003097:Collateral Circulation; D003326:Coronary Circulation; D004285:Dogs; D006339:Heart Rate; D008955:Models, Cardiovascular; D009203:Myocardial Infarction / Q000473:pathology* / Q000503:physiopathology; D009206:Myocardium / Q000473:pathology*; D012306:Risk