Identification of a novel therapy for prevention of sudden death by ischemic cardiac infarction is an area of intensive investigation. We here report that the mortality due to an experimental acute myocardial infarction (AMI) was markedly increased in mice deficient in alpha2-antiplasmin (alpha2-AP(-/-) mice) but not in mice deficient in other components acting in fibrinolysis (tissue-type PA, urokinase type PA, or plasminogen activator inhibitor-1) even if the infarct area in alpha2-AP(-/-) mice was not different from those in the other mice. Echocardiography showed in alpha2-AP(-/-) mice after AMI an overload of the right ventricle and that pulmonary permeability was increased. According to the experiments using explanted myocytes and vascular smooth muscle cells, it was found that the amount of secreted vascular endothelial cell growth factor (VEGF) in alpha2-AP(-/-) mice was markedly increased compared with that in wild-type mice. Finally, an injection of an anti-VEGF antibody decreased the mortality after AMI in alpha2-AP(-/-) mice. Plasmin cleaves extracellular matrix-bound VEGF to release a diffusible proteolytic fragment and is inactivated mainly by alpha2-AP. Therefore, lack of alpha2-AP could markedly result in overrelease of VEGF by the continuous activation of plasmin because of AMI and could result in an acute cor pulmonale. Our results provide new aspects on the role of alpha2-AP and VEGF in the pathogenesis of cardiac events.