Screening capabilities of the lead I electrocardiogram

The lead I R-wave amplitude, T-wave amplitude and T-intercept of 183 persons having normal twelve-lead electrocardiograms (EKGs) and no evidence of heart disease judged by normal history, physical findings, chest X-ray and exercise EKG were compared with the same values in 179 persons who had been hospitalized for heart disease with clinical and electrocardiographic evidence of coronary insufficiency and old myocardial infarction and who had abnormal EKGs with upright T-waves. The purpose of the study was to determine the sensitivity and specificity of various measurements from the lead I EKG among persons without flat or inverted T waves. It was found that significant differences existed between the normal and abnormal groups in all three lead I measurements. The greatest differences were in the T-amplitude and T-intercept. The utility of these two measurements as differentiators between diseased and non-diseased persons was investigated. The diagnosis most reliably detected by the criteria was cardiac ischemia. The low sensitivity of this technique in inferior wall myocardial infarction, right bundle branch block and right ventricular hypertrophy is discussed. Since the values of all three measurements were found to decline with age in both diseased and non-diseased, cut-off values for screening with lead I criteria may need to be related to the age of the screenee.