Lateral and anterior reciprocal electrocardiographic changes: relationship to ST segment elevation and underlying coronary artery disease in inferior myocardial infarction.

The electrocardiogram in patients with acute inferior myocardial infarction frequently displays ST depression in non-infarct leads. The significance of this finding is uncertain. The relationship between ST depression, ST elevation and arteriographic severity of coronary artery disease was explored. 22 patients with acute inferior myocardial infarction, receiving thrombolysis and undergoing acute (within seven hours of the onset of chest pain) coronary angiography were studied prospectively. The electrocardiographic ST segment elevation in the inferior leads and ST segment depression in the lateral and in the anterior precordial leads were measured. In each group of leads, the maximum value of ST deviation in any lead as well as the sum of the values for ST deviation in the individual leads was determined. Gensini scores of total coronary artery disease and component scores for the major coronary arteries were determined from the coronary arteriogram. There was a strong correlation of maximum inferior ST elevation with both maximum lateral ST depression (r = 0.96, p < 0.001) and with maximum anterior precordial ST depression (r = 0.78, p < 0.001). The corresponding correlations for sum of ST deviations were r = 0.91, p < 0.001 and r = 0.79, p < 0.001 respectively. There was no relationship between Gensini scores of coronary artery disease and measures of electrocardiographic ST segment depression or elevation. Electrocardiographic ST depression in non-infarct leads in patients with inferior myocardial infarction, does not provide information regarding the degree of coronary artery disease. The ST depression in both lateral and anterior precordial leads correlates with and is a reflection of inferior ST elevation.