The Missing Waveform Information in the Orthogonal Electrocardiogram (Frank Leads)

Abstract

A new lead system recording nine surface ECGs was found capable of resynthesizing in each patient all the QRS waveforms recorded on the thoracic surface. Observations were made in 416 patients: 150 normal (N) individuals, 95 patients with left ventricular hypertrophy (LVH), 97 patients with right ventricular hypertrophy (RVH), and 74 patients with biventricular hypertrophy (BVH). After time-normalization and division of the nine waveforms into eight equal parts, 72 variables were determined for each patient. Recordings from Frank XYZ leads were also available for each subject. After time-normalization and division in eight equal parts, 24 variables were obtained from Frank lead recordings in each individual. The 72 variables from the new system and 24 variables from the Frank leads were then submitted to multivariate statistical procedures in order to differentiate BVH from N, LVH, and RVH. Four parameters were finally retained — for both the 9-lead system and the Frank leads — as the best discriminators for the separation of BVH from normal, BVH from LVH, and BVH from RVH. The diagnostic performances, defined as ½ (specificity + sensitivity), were 93.5%, 85%, and 81%, respectively, for the 9-lead system and 88.5%, 69%, and 75% for the Frank leads. The repeatability of the results was tested on independent control samples and found reasonable. The limited clinical use of independent pairwise comparisons is discussed and the alternative of stepwise pairwise comparisons following a decision tree is proposed. Some deterioration in the final classification is noticed; the recognition rates are 90% for normal, 79% for LVH, 75% for RVH and 73% for BVH (average 79%) with the 9-lead system, and 90% for N, 55% for LVH, 46% for RVH and 59% for BVH (average 62%) with the Frank leads.