It has previously been shown that analysis of coronary morphology can separate unstable from stable angina. An eccentric stenosis with a narrow neck or irregular borders, or both, is very common in patients who present with acute unstable angina, whereas it is rare in patients with stable angina. To extend these observations to myocardial infarction, the coronary morphology of 41 patients with acute or recent infarction and nontotally occluded infarct vessels was studied. For all patients, 27 (66%) of 41 infarct vessels contained this eccentric narrowing, whereas only 2 (11%) of 18 noninfarct vessels with narrowing of 50 to less than 100% had this lesion (p less than 0.001). In addition, a separate group of patients with acute myocardial infarction who underwent intracoronary streptokinase infusion were also analyzed in similar fashion. Fourteen (61%) of 23 infarct vessels contained this lesion after streptokinase infusion compared with 1 (9%) of 11 noninfarct vessels with narrowing of 50 to less than 100% (p less than 0.01). Therefore, an eccentric coronary stenosis with a narrow neck or irregular borders, or both, is the most common morphologic feature on angiography in both acute and recent infarction as well as unstable angina. This lesion probably represents either a disrupted atherosclerotic plaque or a partially occlusive or lysed thrombus, or both. The predominance of this morphology in both unstable angina and acute infarction suggests a possible link between these two conditions. Unstable angina and myocardial infarction may form a continuous spectrum with the clinical outcome dependent on the subsequent change in coronary supply relative to myocardial demand.

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Aggregated platelets and occlusive platelet thrombi were found in small myocardial vessels of dogs on electron-microscope examination after prolonged infusion of norepinephrine. The etiology of the myocardial necrosis and fibrosis induced by catecholamines in experimental animals and seen in patients with pheochromocytoma and patients after norepinephrine treatment for shock may be related to this intravascular platelet-aggregating effect of catecholamines. The link between stress and acute myocardial infarction may be via catecholamine-induced intravascular platelet thrombosis. If the thrombogenic theory of atherosclerosis is valid, platelet aggregation induced by catecholamines may be the mechanism whereby arteriosclerotic heart disease is related to stress.

The pattern of complete right bundle-branch block (RBBB)

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