The Roentgen Classification and Diagnosis of Cardiac Alignments

Within the past few years, there has been increasing interest in alignments of the cardiac chambers and great vessels. The entire subject has been immensely confused due to lack of a standard, accepted terminology and classification of these anomalies. Many of the terms in common use, such as corrected transposition, dextroversion, etc., have been subject to considerable criticism. Such a situation invariably engenders further confusion and impedes progress. Several classifications have been published (3, 7, 8, 10, 20, 22, 27, 28, 30) in recent years. These classifications treated the subject with varying thoroughness and, in general, employed different designations for the several entities involved. Indeed, definitions of terms vary from one classification to another. Great stress has been placed upon alignments encountered in dextrocardia, although it is recognized that the reverse of all dextrocardia alignments are encountered when the heart is in the left side of the thorax. The brilliant contributions of Van Praagh et al. (26–30) provide an acceptable embryological explanation for virtually all cardiac alignments. A classification system, based on patterns of blood flow, was developed at the University of Kentucky in 1964 (20). Continued experience has permitted simplification and extension of our classification system. This system is consistent with the embryological explanations offered by Van Praagh et al. A careful roentgen examination, particularly biplane angiocardiography, permits accurate identification and classification of all basic cardiac alignments in virtually every situation, as well as variants such as common ventricle or origin of both great vessels from the right ventricle. Definitions Precise definitions are essential to avoid confusion and to promote clarity. Care has been exercised to keep the terminology as simple and interrelated as possible, since problems with some other systems concern the numerous entities involved and rather abstruse terminology. Our current terminology is simpler and slightly different from that originally published by this author (20). The terminology of this classification is shown in TABLE I. “Right” and “left,” in designating the atria and ventricles, describe only morphology and have neither functional nor positional connotations. Consequently, a right atrium may be located on either the right or the left side of the thorax. When location of a cardiac chamber is described, a qualified right or left, such as right-sided or left-sided, is preferred. It is necessary to define relationships between the atria and the ventricles. As is well known, a right atrium may discharge blood into either a right ventricle or a left ventricle. The ventricles are said to be “inverted” when the right atrium feeds the left ventricle and the left atrium feeds the right ventricle, regardless of their laterality.