The natural history of left ventricular thrombus in myocardial infarction: A rationale in support of masterly inactivity

AbstractOne hundred five unselected and consecutive patients were prospectively studied after acute transmural myocardial infarction to assess the incidence of mural thrombus formation and to relate the presence of thrombus to patient outcome in terms of systemic embolic events, functional class and survival. In 87 patients, optimal quality two-dimensional echocardiographic studies were obtained and were repeated at daily intervals to detect mural thrombus formation. The site of infarction was anterior in 53 patients and inferior in 34. On admission, all patients received subcutaneous heparin and antiplatelet agents (aspirin, dipyridamole); none received full anticoagulant therapy.Left ventricular mural thrombus was visualized between 2 and 11 days (median 6) after the clinical onset of infarction in 21 (40%) of the 53 patients with anterior infarction. No patients with inferior infarction had echo-cardiographic evidence of thrombus formation. During follow-up of 22 to 51 months (mean 39), none of the 21 patients with mural thrombus had clinical evidence of systemic embolism. One patient with inferior and one with anterior infarction had a cerebral embolus 7 days and 9 months, respectively, after the acute event, but neither of these patients had echocardiographic evidence of left ventricular thrombus at any stage. Echocardiography performed at 1 and 2 years of follow-up showed persistent evidence of thrombus in only 8 (31%) and 5 (24%) of the 21 patients, respectively.On admission, the functional class of patients with anterior myocardial infarction and thrombus was similar to that of patients without ventricular thrombus. Early in-hospital mortality was higher in those without thrombus (9 [28%] of 32 versus 2 [9%] of 21) (p < 0.001) and occurred earlier in time (mean 24 h versus 8 days) (p < 0.001). At 1 year of follow-up, patients with anterior infarction and thrombus formation had improvement in functional class compared with those who did not (p < 0.001).It is concluded that left ventricular mural thrombus is a common finding in patients sustaining anterior myocardial infarction. The incidence of systemic embolism, however, is low and does not justify full anticoagulation. Furthermore, as early mortality and morbidity were lower in patients wioh than in those without mural thrombus, mural thrombus, by offering mechanical support to infarcted myocardium, may protect against left ventricular rupture and improve functional class in the long term