In a group of patients with previous myocardial infarction S.T.I. are evaluated by polygraphic method. In all examined patients an increment of Pre ejection period (PEP) has been observed caused by the increase of the Deformation time (Q-S1). Increased values of SFW/RFW ratio are observed in dyastolic phase. The Authors, in absence of other meccanocardiographic alterations, have ascribed the anomaly to the alteration of the myocardial contraction because of previous necrosis.