Consider, for example, transposition of the great arteries (TGA). At the present time, TGA is defined and named with reference to the anatomy of the normal heart. Compared with the normal human heart, in TGA the aorta is placed across the ventricular septum (Latin, trans, “across,” and positio, “a placing”), and consequently the aorta arises above the anatomically inappropriate ventricle, the morphologically right ventricle. Similarly, the transposed pulmonary artery has been “placed across” the ventricular septum and thus originates above the anatomically inappropriate ventricle, the morphologically left ventricle.
Complete TGA meant transposition of both great arteries, usually typical D-TGA. Partial TGA meant transposition of only one great artery, typically the aorta. We now call this double-outlet right ventricle (DORV). Rarely, only the pulmonary artery is transposed, resulting in double-outlet left ventricle (DOLV). Thus, partial TGA includes both DORV and DOLV.
By the late 1920s, any spatial anomaly between the great arteries themselves, and/or between the great arteries and the underlying ventricles, was regarded as some form of TGA—complete or partial. So “transposition” of the great arteries included “everything.”
But gradually, more accurate and specific terminology emerged. People who are interested in languages and meanings started using transposition of the great arteries with literal accuracy, that is, only for cases in which it looked as though both great arteries had been placed across the ventricular septum (Latin, trans + positio, or English, transposed) and thus both great arteries arose above the morphologically wrong ventricles. This change caught on because it was based on accuracy in terminology.
When you do this, the names of a lot of other anomalies have to change because transposition of both great arteries is not present, accurately speaking. Anomalies that had to have their names changed include:
double-outlet right ventricle (DORV) ;
double-outlet left ventricle (DOLV) ;
anatomically corrected malposition of the great arteries (ACMGA) ; and
absence of subpulmonary infundibulum (AOSPI), erroneously known as truncus arteriosus communis.
Now, our diagnoses are anatomically accurate, that is, relative to normal cardiac anatomy. However, developmentally, our anatomic diagnoses are often erroneous. Consider D-TGA ( Table 30.1 ):