Left ventricle (LV) disfunction is the main cause of death in patients suffering from acute myocardial infarction (AMI) who are admitted to Coronary Care Units. Therefore, it is easily understandable that the study of LV performance is of paramount importance in the choice and evaluation of the efficacy of therapy, as well as in the prognosis of patients with AMI. In the first section of this paper, the authors analyze the physiopathology of LV disfunction during AMI; in the second section, based upon a study of 480 patients, they value the contribution of hemodynamic examination with the Swan-Ganz catheter in the evaluation of the cardiac function and in the prognosis of patients with AMI.