In patients with severe heart failure due to acute myocardial infarction (AMI) breathing with PEEP can be of additional therapeutic value. This study was designed to assess the effects of CPAP through face mask with 15 cm H2O on left ventricular performance in AMI patients, using equilibrium radionuclide angiocardiography (ERA). In response to lung inflation, high levels of PEEP have been shown to decrease heart rate and stroke volume. The sum of the TPF pathological prolongation and the Mean-FR reduction suggests a decrease in the left ventricular compliance determined by the restriction imposed by the positive pressure. The global systolic performance is preserved.