II. Diagnosis of Left Ventricular Hypertrophy and Myocardial Infarction from "Total" Surface Waveform Information

Eight surface leads were found to account for the "total" waveform information in 282 patients (145 normal subjects, 59 patients with LVH, and 78 with myocardial infarction). In each patient the Frank leads were also reconstructed. After time normalization of the eight leads and the XYZ leads and division of the QRS complex into eight equal parts, the resulting variables (64 in the eight lead system and 24 in the Frank lead system) were submitted to multivariate statistical procedures. In a first step, the variables which proved best for the differentiation between normal records and those from patients with LVH or myocardial infarction were selected through stepwise discriminant analysis. A discriminant function was then computed and applied to both pathological groups. The results clearly point up the superiority of the eight lead system. With the level of specificity kept constant at 95%, 91% of the patients with LVH and 95% of the patients with myocardial infarction were correctly classified. With the Frank leads 83% and 85%, respectively, were recognized. The reproducibility of the results also proved to be better with the eight lead system.