cAn Official Journalofthe c_American Heart cAssociation, Inc. ORIGINAL ARTICLES The Relationship Between Acute Occlusive

SUMMARY A prospective study was done on 100 hearts from patients who had clinically proved myocar-dial infarction with histologic confirmation. The following variables were considered and related statistically: age, set and duration of patient survival; heart weight; type, form, length and degree of preexisting stenosis in the coronary system; the location and type of coronary occlusion; the location, type and size of an infarct and the other forms of irreversible myocardial damage found. Fifty-five percent of the hearts had no occlusive thrombus in the coronary artery supplying the infarcted myocardium. In 45 cases in which thrombi were found, all but one were in a supplying coronary artery. The occurrence of thrombi was associated with an increased size of infarct, most frequently with transmural infarcts (55%) and less often with those involving the inner two-thirds of the wall (30%) or with subendocardial infarcts (27%). Most infarcts developed in patients with 70% stenosis in the coronary artery system, although the size of an infarct was independent of the number, degree, length and distribution of severe stenoses found in the system. A supplying artery usually showed a stenosis of> 70 % along its course or, if it contained an acute occlusive thrombus, the thrombus was at a stenosis caused by an atheromatous plaque. These data support the concept that an occlusive coronary thrombus has no primary role in the pathogenesis of a myocardial infarct. Two other morphologic forms of myocardial necrosis were found associated with infarcts. Their pathogenesis and role in an acute infarction must be clarified