Is the aorta truly dextroposed in tetralogy of Fallot? A two-dimensional echocardiographic answer.

Abstract

The embryogenesis of tetralogy of Fallot is still much debated. In particular, the dextroposition of the aorta is not considered by all pathologists as a genuine abnormality in this congenital heart disease but rather as a false impression due to an exaggeration of the normal overriding caused by dilatation of the aorta secondary to abnormal hemodynamics. We used two-dimensional echocardiography to examine the spatial position of the aortic root in 22 patients with tetralogy of Fallot (aged 5 days to 24 years, mean 6.4 years) and in 23 normal subjects (aged 1 month to 27 years, mean 7.6 years). Using the parasternal short-axis view, we determined the percent rightward displacement of the aortic root in relation to the plane of the atrial septum, and the relationship between the aortic cusps and the atrial septum. We measured the value of the angle 0, which was defined as the angle between the plane of the atrial septum and the plane of the left coronary-noncoronary commissure and leaflet appositional plane. In the control group, the aortic root was displaced to the right by only 23.6 + 7.6%; the atrial septum crossed the posterior aspect of the aortic root at the middle (n = 19) or at the right half of the posterior cusp (n = 4), and the angle 0 had a value of 43.3 + 8.8 degrees. In the 22 patients with tetralogy, the percent rightward shift of the aortic root was augmented to 55.5 + 9% (p < .001) and the atrial septum was related to the posterior commissure in 14 patients, to the left coronary cusp in two patients, and to the left fourth of the posterior cusp in six patients; the angle 0 had a value of 9.2 11.2 degrees (p < .001). In the two groups, the position of the commissure between the right coronary and left coronary aortic cusps was similar in relation to a line passed forward from the atrial septum. We conclude that the aorta is truly dextroposed in tetralogy of Fallot, with a rightward shift due to a clockwise rotation of the aortic root (looking downstream), and that the axis of this rotation is the anterior aortic commissure. Our echocardiographic findings, which confirm conclusions of previous investigators based on pathologic anatomy, support the embryologic hypothesis of the lack of conal rotation in tetralogy of Fallot and permit a quantitation of the effects of this morphogenetic mechanism. Circulation 73, No. 5, 892-899, 1986. IN THE PAST, the terms "dextroposition" and "overriding" have been used interchangeably. However, overriding of the aorta should not be confused with dextroposition. Overriding of the aorta over the right ventricle occurs in the normal heart because of the sigmoid interventricular septum' as well as in hearts with isolated infundibular perimembranous ventricular septal defect2' 3 and can be considered a normal anatomic feature.4 The term dextroposition indicates a pathologic condition with a rightward displacement of the aortic root.4' There has been considerable debate concerning whether a true dextroposition of the aorta exists in tetralogy of Fallot. Some ...

The Eisenmenger malformation: a morphologic study

“…Others have assessed the relationships between the zone of apposition between two coronary leaflets of the aortic valve and the zone of apposition between the adjacent leaflets of the pulmonary valve, showing that this does not change according to the extent of aortic override. 7,21 Our findings suggest that, as the dorsal component of the aortic root rotates rightward, its overall axis is displaced leftward, correlating in this way with the observations regarding the interrelations of the zones of apposition between the adjacent valvar leaflets (Fig 7). In other words, the Figure 7.…”

Variations in rotation of the aortic root and membranous septum with implications for transcatheter valve implantation

“…This crucial structure penetrates the atrioventricular component of the septum as it extends to reach the left ventricular outflow tract 12. Rotation of the aortic root is well recognised in the setting of congenitally malformed hearts, such as those with tetralogy of Fallot 13. Normal variation, in contrast, is less well appreciated 10 13 14.…”

Correlating the morphological features of tetralogy of Fallot and the Eisenmenger malformation

“…The cases also showed the comparable variation in terms of the rightward deviation of the aortic root. 9,17 Thus, in those with frontal attachment of the outlet septum, the anterior commissure between the coronary leaflets of the overriding aortic valve, which was established to represent the axis of rightward rotation of the aortic root, 9,17 was in line cranially with the right posterior surface of the anterosuperior limb of the septomarginal trabeculation (Fig 3). This frontal insertion of the outlet septum and the position of the anterior aortic valvar commissure were maintained independently of the extent of rightward position of the aortic root (compare Figs 3 and 8a).…”