SUMMARY A new coding system for ECG abnormalities was developed, based on Frank's orthogonal ECG leads. In contrast to other systems, such as the Minnesota Code (MC), the new system was based on data collected prospectively in a cooperative study of 5031 records. The records were classified solely on the basis of non-ECG information. A record sample from normal women was also available. The large data base allowed stratification of ECG criteria according to sex and race.ECG criteria were determined at two levels of sensitivity and specificity. Specificity was 80-100% at the first level and 90-90% at the second.The new system has fewer criteria than other codes, which leads to reduction of coding errors and coding time. For common problems in differential diagnosis, optional criteria were included. A computer program for automated coding was also developed.THE ECG is a standard tool in epidemiologic studies of cardiovascular disease. To report ECG findings in uniform, clearly defined terms, Blackburn et al.1 introduced the Minnesota Code (MC), which has been widely used.The original MC was based on the more reliable and generally accepted diagnostic criteria known at that time (1960). Little was known then about actual distributions of ECG findings in large populations, and the criteria proved to have a large observer variation.2 Another serious shortcoming was the lack of information on the effect of constitutional variables on the ECG, which was later studied extensively.:", Thus, a code based on actual ECG data from large normal and abnormal populations that takes into account differences in ECG findings according to sex and race would be desirable. In the present study, we attempted to take these factors int-o consideration.Corrected orthogonal leads have contributed substantially to a better understanding of ECG lead performance and are being used in most of the larger epidemiologic studies. One major advantage of these leads is the substantial data reduction (12 may not be in agreement with the original Frank lead data.The availability of a large documented ECG library was significant in selecting the Frank lead system for the new code. Based on standardized, ECG-independent clinical information,9 '7 this library was developed through a Cooperative Study of the Veterans Administration. Eight hospitals participated.To reduce coding time and coding errors, the new system was kept as simple and convenient as possible. Material and MethodsThe samples used to develop the code are listed in table 1. The selection criteria have been described in deta'l,9-17 but a brief summary will be given here.The records from normal subjects9' 17 were obtained from 1049 adult men and 450 adult women. The age and race distributions of these subjects are shown in figure 1. All patients had a complete history, physical examination and routine laboratory tests. All subjects who had diseases that frequently predispose to cardiovascular disease (diabetes mellitus, pulmonary disease, renal disease, hypertension, anemia and collagen ...

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