The American journal of cardiology
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The purpose of this study was (1) to establish the maximal interval between the onset of ischemia and reperfusion that would permit a decrease in the size of infarction, and (2) to evaluate the relation between changes in infarct size and preservation of cardiac function. Studies were carried out in 19 dogs of which 13 had temporary (1 to 3 hours) occlusion of the left anterior descending coronary artery. The hospital course of 15 patients of whom 13 underwent myocardial revascularization within 8 hours of acute infarction was also reviewed. ⋯ In spite of successful revascularization, electrocardiographic evidence of transmural infarction persisted postoperatively. It is concluded that reperfusion of an area of myocardium that has been ischemic for less than 2 hours in dogs or less than 4 hours in man may lead to a significant reduction in the extent of infarction as well as improvement in cardiac function. However, the revascularized area remains angiographically dyskinetic and electrocardiographically abnormal.
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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. ⋯ 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.
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Comparative Study
Maximal revascularization (reperfusion) in intact conscious dogs after 2 to 5 hours of coronary occlusion.
Acute infarction was produced in intact conscious dogs by inflating a previously implanted balloon cuff around the left anterior descending coronary artery was occluded in 26 control dogs and reperfused by deflating the balloon cuff after 2 hours of occlusion in 19 dogs (group II) and after 5 hours in 11 dogs (group III). Serial studies were performed and repeated after 48 hours and 7 days. All three groups revealed hemodynamic and metabolic deterioration with coronary occlusion and infarct production. ⋯ Infarct size was more than 15 percent of ventricular mass in 92 percent of control dogs and in 100 percent of dogs in group III, but in only 50 percent of those in group II. The data indicate that reperfusion in conscious dogs representing early, noninvasive maximal revascularization under ideal circumstances fails to prevent deterioration or death; instead it hastens the development of arrhythmias and myocardial injury. Reperfusion, although deleterious in the first hours, can reduce infarct size if performed after 2 hours, but not after 5 hours, of occlusion.
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The Starr-Edwards ball valve prosthesis is generally the standard by which other cardiac valve substitutes are compared. This report reviews information pertaining to several prostheses--the Beall mitral valve and the Bjork-Shiley, Braunwald-Cutter, Lillehei-Kaster and Smeloff-Cutter aortic and mitral valves--considered by some to have specific advantages over the Starr-Edwards valves. Hospital and late mortality rates after valve replacement are comparable for the four aortic valve prostheses reviewed and depend more on patient selection than on the specific prosthesis utilized. ⋯ On the basis of postoperative data, the five mitral valve prostheses reviewed do not appear to have substantial hemodynamic differences. For patients with a small left ventricular cavity the low profile prostheses, such as the Beall, Bjork-Shiley and Lillehei-Kaster, may be advantageous. Most available evidence indicates that patients receiving aortic or mitral valve prostheses should be given anticoagulant therapy postoperatively.
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Advanced actuarial techniques are used to analyze late results in 912 patients who had isolated mitral or aortic valve replacement with ball valve prostheses from 1965 to 1974. Experience with noncloth-covered and cloth-covered valves is compared in terms of late survival, rate of thromboembolic complications and reoperation and the influence of anticoagulation. The cloth-covered prostheses have substantially reduced the incidence of emboli after mitral valve replacement (1.9 vs. 6 emboli per 100 patient years) and have thus far eliminated emboli after aortic valve replacement in patients receiving warfarin. ⋯ This should be prevented in the new model 2400 composite strut ("track") valve by a narrow metal track on the inner surface of each strut. The substantial recent reductions in operative mortality and in prosthesis-related complications pose important questions regarding timing of operations and selection of prostheses. These decisions must be individualized for each patient on the basis of a thorough analysis of late results using modern statistical methods.