SUMMARYNine 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.
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.
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 1/2 (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.BVH resulted in a correct classification of 44% of the
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