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

Abstract

Nine surface electrocardiograms recorded on the thoracic surface at fixed and identical locations in 412 individuals were found to account for the maximal useful waveform information available in each individual. In other words, nine waveforms were capable of resynthesizing any waveform recorded on their thoracic surface. These nine waveforms were then submitted to multivariate statistical procedures and their diagnostic performance compared to the Frank leads on which the same procedures were applied. Before the data were fed into the computer, all waveforms were time-normalized and divided into eight equal parts, yielding 72 variables and 24 variables for the nine lead system and the Frank leads, respectively, for each individual. In this paper we attempted to discriminate between normal subjects and patients with documented angina pectoris (typical history and positive coronary angiography); myocardial infarction was excluded in these patients. Only the resting QRS complex was considered. With the 9-lead system, keeping the specificity (true negatives) at 90%, the sensitivity (true positives) is 76%; with the Frank leads, the same specificity yielded a sensitivity of 49%. The repeatability of the results on new independent controls was also found very satisfactory. The discrimination between patients with angina pectoris on one hand and left ventricular hypertrophy and myocardial infarction on the other hand resulted in a performance level of 89% and 87%, respectively, for the 9-lead system. A good correlation was also found between the extent of the coronary lesions (number of coronary vessels involved) and the fraction of correctly diagnosed patients. The present study concluded that the retrieval of more complete surface information results in an evident improvement of the diagnostic performance of electrocardiography.