Electrocardiographic Surface Mapping of the Heart Following Myocardial Infarction and the Influence of Beta-blockade

It is generally accepted that ST segment elevation is one of the characteristic electrocardiographic features of acute myocardial infarction. In experimental myocardial infarction the degree of ST segment elevation has been related to the degree of change in coronary flow. Surface mapping in patients of the electrocardiographic potentials gives an indirect representation of the epicardial ST segment change and in indication of the area of underlying myocardial damage. A number of patients who had sustained myocardial infar-tion within 72 hours were studied. All the patients had a history of prolonged ischaemic cardiac pain, electrocardiographic changes and a rise in serum enzymes. Electrocardiagrams were recorded from 72 points on the chest surface. Control maps were constructed from the ST segment changes measured at each of these points and plotted on a standard diagram. Electrocardiograms were recorded during a control period immediately before 20 mg of practolol was given intravenously over a period of five minutes. In all patients practolol produced a significant reduction in the area of ST segment elevation as represented by a reduction in the number of points with ST elevation of more than 2 mm. The significance of these findings is discussed.