Objectives: The management of mural thrombus complicating acute anterior myocardial infarction remains controversial in part because of the small size of studies on this topic. We performed a meta-analysis of published studies to address three questions: 1) What is the embolic risk of mural thrombi after myocardial infarction? 2) What is the impact of systemic anticoagulation in reducing the embolic risk of mural thrombi? 3) What is the impact of systemic anticoagulation, thrombolytic therapy and antiplatelet therapy in preventing mural thrombus formation?
Methods: Studies were identified by a computerized and manual search and were included if they were published in manuscript form in the English-language literature. Pooling of data was performed by calculating the Mantel-Haenszel odds ratio and an event rate difference by the method of DerSimonian and Laird.
Results: The odds ratio for increased risk of emboli in the presence of echocardiographically demonstrated mural thrombus (11 studies, 856 patients) was 5.45 (95% confidence interval [CI] 3.02 to 9.83), and the event rate difference was 0.09 (95% CI 0.03 to 0.14). The odds ratio of anticoagulation versus no anticoagulation in preventing embolization (seven studies, 270 patients) was 0.14 (95% CI 0.04 to 0.52) with an event rate difference of -0.33 (95% CI -0.50 to -0.16). The odds ratio of anticoagulation versus control in preventing mural thrombus formation (four studies, 307 patients) was 0.32 (95% CI 0.20 to 0.52), and the event rate difference was -0.19 (95% CI -0.09 to -0.28). The odds ratio for thrombolytic therapy in preventing mural thrombus (six studies, 390 patients) was 0.48 (95% CI 0.29 to 0.79) with an event rate difference of -0.16 (95% CI 0.10 to -0.42), whereas for antiplatelet agents (two studies, 112 patients) the odds ratio was 1.43 (95% CI 0.04 to 56.8) with an event rate difference of 0.16 (95% CI -0.20 to 0.52).
Conclusions: This analysis supports the hypotheses that 1) mural thrombus after myocardial infarction poses a significantly increased risk of embolization, 2) the risk of embolization is reduced by systemic anticoagulation, and 3) anticoagulation can prevent mural thrombus formation. Thrombolytic therapy may prevent mural thrombus formation, but evidence for a similar benefit of antiplatelet therapy is lacking.