Abstract Two patients with rheumatic heart disease with mitral stenosis are reported, both of whom were operated upon for the purpose of performing a mitral valvuloplasty. Both patients were closely followed electrocardiographically. During the operation, surgical emergency therapy resulted in the ligation of the left coronary artery. The pattern of acute myocardial infarction appeared in both cases. It proceeded to rapid death in one case and regressed in the other. At post-mortem examination, both showed the suspected ligation, and the histological picture of an infarcted myocardium of the appropriate age was found. The cases are discussed with respect to (1) possible influence of shock and hemorhage, (2) electrocardiographic pattern and time relationships, (3) the pathology involved, and (4) possible explanations of the reversion of the electrocardiographic pattern in the second case.