Editorial: Prevention of heart disease by control of risk factors: the time has come to face the facts.
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Biomedical subjects
Publications and source records attributed to E Corday.
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Two experimental series of closed chest dogs were compared: Group A (five dogs with 7 days of continuous occlusion of the proximal left anterior descending coronary artery); and Group B (six dogs with 7 days of reperfusion after 3 hours of acute occlusion of the same artery). Hemodynamic measurements, ventricular wall motion, coronary sinus blood flow and regional metabolism in both coronary occluded and nonoccluded segments of the left ventricle were measured sequentially. The infarct size was characterized by detailed histopathologic analysis. In the control dogs (Group A), mechanical and metabolic function remained severely depressed after 7 days of occlusion, and mean infarct size was 31.6 percent. In Group B, significant mechanical and metabolic dysfunction developed during 3 hours of occlusion and did not improve during the 1st hour of reperfusion. However, after 7 days of reperfusion, function returned to near preocclusion level. Mean infarct size was 14.2 percent, but in two of the six dogs infarct size was 43 percent and 23 percent, respectively. The study confirmed the unstable character of the early phase of reperfusion, attributed to cell swelling, edema and hemorrhages that resulted in inadequate coronary reflow, arrhythmias and functional derangements. Prolonged reperfusion for 7 days reduced mean infarct size and improved cardiac function.
Focal necrosis (microinfarcts) and regional lactate derangements were observed in closed chest dogs in the nonoccluded (remote) posterior segments of the left and right ventricles after acute occlusion of the proximal left anterior descending coronary artery. Focal infarcts in the remote areas were observed in five of the six dogs with 7 days of occlusion of the left anterior descending artery and in six of seven dogs with 7 days of reperfusion after 3 hours of occlusion. There was a good correlation between the finding of microinfarcts and myocardial lactate derangements in the corresponding remote myocardium. No significant lactate derangements or microinfarcts were found in sham experiments. These findings suggest that ischemia of the remote myocardium frequently accompanies an acute coronary occlusion and may result in irreversible focal lesions.
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Regional measurements of the consequences of coronary artery occlusions indicate myocardial derangements in both the coronary occluded and nonoccluded myocardium. The proximal left anterior descending coronary artery (LAD) was acutely occluded in 34 closed-chest anesthetized dogs through inflation of an intracoronary balloon. Temporary seperation of venous compartments was achieved by means of a balloon catheter placed within the great cardiac vein, and simultaneous blood sampling from both occluded and nonoccluded segments was carried out. Acute coronary occlusion resulted in early cardiac dysfunction which persisted during the subsequent 3 hours of LAD occlusion. Oxygen extraction increased 6-8% in both occluded and nonoccluded zones. Lactate extraction in the nonoccluded segment decreased significantly from 34.4 to 23.7% (P less than 0.05). In the occluded zone, lactate extraction dropped from 35.0 to 7.8% (P less than 0.05). Of the 34 dogs studied, 17 exhibited lactate production in the occluded segment, while 7 dogs also had lactate production in the nonoccluded region. Significant postocclusion myocardial potassium efflux was noted in both zones.
The sequential effects of reperfusion following acute intracoronary balloon occlusion were investigated in closed-chest anesthetized dogs by simultaneous measurement of hemodynamics and regional metabolism and histopathologic study. Simultaneous regional determinations of myocardial metabolic function were carried out in coronary-occluded and nonoccluded segments of the left ventricle. A 3-hour occlusion of the proximal left anterior descending coronary artery (LAD) resulted in significant decrease in cardiac function. Intitial reperfusion was marked by major washout of metabolites and development of frequently serious arrhythmias. Reperfusion following 3 hours of LAD occlusion led to futher deterioration in hemodynamics and metabolism: 30% of the dogs developed shock. Lactate extraction decreased further in the nonoccluded region and reached production levels in the occluded zone. Potassium loss increased in both zones. Oxygen extraction remained unchanged. Pathophysiologic examination of tissue specimens from the reperfused zone revealed microthrombi, patchy necrosis, fragmentation of myofibrils, vascular congestions, and hemorrhages.
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