The missing waveform and diagnostic information in the standard 12 lead electrocardiogram.

Summary Body surface potential data from 562 subjects were used to determine optimal locations of electrocardiographic (ECG) leads for retrieving waveform and diagnostic information which is lost if ECG recording is limited to the standard 12 leads. The essence of this approach rests on the empirical evidence obtained by testing each of the 128 simultaneously recorded surface ECGs for the standard leads content using a least squares best fit procedure. The poorly fitted curves are considered as additional waveform sources; the number and the sites of this additional signal information are then determined. The total QRS-ST surface waveform information is found to be represented by the standard 12-lead ECG whose eight independent components were supplemented with four additional surface leads (“supplemented” standard lead system). As an alternative to this set of 12 waveforms, a lead system consisting of nine directly recorded, non-redundant surface ECGs was also designed and found capable of accounting for the same total waveform information (“substitute” 9-lead system). The diagnostic accuracy of both lead sets is compared with the standard 12 leads and the Frank leads in differential diagnosis between normal individuals and patients with myocardial infarction. Results both in the training group (277 subjects) and in the testing group (200 subjects) reveal that the diagnostic content of the Prank leads is less than that of the standard 12-leads. The Frank leads combined with the standard leads improve moderately the diagnostic information yield. The fraction of correctly classified subjects amounted to 79%, 83%, 88%, 95% and 95% for the Frank leads, the standard leads, the combined Frank leads and standard leads, the “supplemented” standard leads and the “substitute” 9-leads, respectively. The results obtained with the standard leads and compared with those achieved by other lead systems, both better and worse as far as the waveform information is concerned, indicate that the retrieval of more complete signal information undoubtedly improves diagnostic performance.