Identification of Best Electrocardiographic Leads for Diagnosing Left Ventricular Hypertrophy by Statistical Analysis of Body Surface Potential Maps

Abstract In view of the increased risk of cardiovascular mortality associated with left ventricular (LV) hypertrophy, early recognition and quantitation of LV hypertrophy are important clinical goals. The standard 12-lead electrocardiogram is the easiest and most widely used noninvasive method for the diagnosis of LV hypertrophy; unfortunately, the diagnostic accuracy of commonly used electrocardiographic criteria remains unsatisfactory. Body surface potential maps contain diagnostic information not present in conventional lead systems. The present investigation combines the increased information content of surface maps with the power of multivariate statistical techniques in order to identify practical subsets of electrocardiographic leads that would allow improved diagnosis of LV hypertrophy. Discriminant analysis was performed on 120-lead data simultaneously recorded in 250 normal subjects and 214 patients with LV hypertrophy using as features instantaneous voltages on time-normalized P, PR, QRS and ST-T waveforms as well as the duration of these waveforms. Leads and features for optimal separation of 173 normal subjects aged ≥30 years from 122 patients with pure LV hypertrophy were selected. A total of 6 features from 5 torso sites accounted for a specificity of 97% and a sensitivity of 94%. The single most potent discriminator was the duration of the P wave; voltages were measured in mid and late P on leads located in the lower left parasternal area, the left precordial region and the upper right back, in mid-QRS on a lead positioned 10 cm below V 1 and slightly before the peak of the T wave on a lead in the lower left flank. These optimal sites for LV hypertrophy diagnosis were in general outside the conventional electrocardiographic lead locations. The discriminant function was then tested on the remaining 77 normal subjects aged 20 to 30 years and 92 patients with complicated LV hypertrophy: a specificity of 95% and a sensitivity of 92% were observed. In comparison, multivariate analysis on the standard 12 leads correctly classified 86% of pure LV hypertrophy patients and 83% of complicated LV hypertrophy cases at specificity rates of 94 and 93%, respectively. Substantial improvement of diagnostic classification can thus be achieved by appropriate selection of electrocardiographic leads from body surface potential maps.