The unidentified information content of the electrocardiogram.

DEVELOPMENT of practical recording methods for the human electrocardiogram was rapidly followed by important medical applications. Electrocardiography was established as the major means of classifying disturbances of cardiac rhythm and an important aid in the recognition of myocardial disease including infarction. Applications have been sufficiently significant to result in widespread use of the method and there have been continuing technological improvements and extensions of the method's utility. At the present time and as presently used, electrocardiography is one of the major medical diagnostic methods. Despite considerable utility, it is unlikely that the full medical significance of electrocardiographic examination has been achieved. A variety of theoretic considerations together with supporting experimental and clinical observations suggest that the record may contain information of equal or even greater medical significance than that now obtained. This communication will review some of these considerations and observations. Material will be presented under the headings of regional cardiac examination, prognostic utility, and extended diagnostic applications. None of these represent totally new objectives for electrocardiographic examination but each offers substantial possibilities for improved use of the technique. The material reviewed does not include all areas in which improvements of electrocardiography are likely and should be viewed only as selected examples. Much of the material is necessarily speculative although some theoretic and/or clinical and experimental support for the speculations in each area will be furnished.