Tetralogy of Fallot: morphological variations and implications for surgical repair

Abstract

Objectives: Tetralogy of Fallot is characterized by anterocephalad deviation of the outlet septum, along with abnormal septoparietal trabeculations, which lead to subpulmonary infundibular stenosis. Archives of retained hearts are an important resource for improving our understanding of congenital heart defects and their morphological variability. This study aims to define variations in aortic override, coronary arterial patterns and ventricular septal defects in tetralogy of Fallot as observed in a morphological archive, highlighting implications for surgical management.

Methods: The Birmingham Children's Hospital archive contains 211 hearts with tetralogy of Fallot, of which 164 were analysed [69 (42.1%) unrepaired and 95 (57.9%) operated specimens]. A detailed morphological and geometric analysis was performed using a rigorous 5-layer review process.

Results: Anomalies were observed in the orifices, origins and course of the coronary arteries: 20 hearts (13.0%) had more than 2 orifices and 3 hearts (1.9%) had a single orifice. In 7 hearts (4.3%), a coronary artery crossed the right ventricular outflow tract. The extent of aortic override ranged from 31.0% to 100% (median of 59.5%). The ventricular septal defect was most often perimembranous (139, 84.8%), but we also found muscular (14, 8.5%), atrioventricular (7, 4.3%) and doubly committed juxta-arterial (2, 1.2%) variants.

Conclusions: Anatomical variations are common and can impact surgical management. Anomalous coronary arteries may require a conduit rather than a transannular patch. Variability in aortic override determines the size of patch used to baffle blood to the aorta. The type of ventricular septal defect affects patch closure and the risk of postoperative conduction defects.

Keywords: Aortic override; Cardiac surgery; Coronary arteries; Morphology; Tetralogy of Fallot.

Figure 1:

Linear method for the measurement of aortic override, as viewed from the left ventricle. The crest of the muscular ventricular septum was taken as the boundary for the aortic leaflets supported by the ventricular structures (red stars). The proportion of the circumference of the aortic root supported by the left ventricle is the sum of the red dashed lines and that supported by the right ventricle is the yellow dashed line.

Figure 2:

Variation in the orifice position and the course of anomalous coronary arteries crossing the right ventricular outflow tract. (A) The high location of the right and left coronary orifices above the sinutubular junction (yellow dashed line). (B) An anterior interventricular artery originating from the right coronary artery and coursing towards the apex. (C) An operated heart, in which the anterior interventricular artery has been dissected, again originating from the right coronary artery, repaired using the 2-patch technique. (D) The aortic root lies to the left of the pulmonary trunk and the right coronary artery crosses the right ventricular outflow tract to achieve its anticipated position in the right atrioventricular groove; a patch has been placed beneath the right coronary artery to avoid incising it.

Figure 3:

Variation in the position of the aortic root (red) with reference to the pulmonary root (blue).

Figure 4:

Histogram demonstrating the range of aortic override using the linear method.

Figure 5:

Bland–Altman plots and histograms of difference for measurements of the degree of aortic override comparing (A) leaflet proportion versus linear methods, (B) leaflet proportion versus qualitative methods and (C) linear versus qualitative methods.

Figure 6:

Morphology of the various types of ventricular septal defect, as seen from the right ventricle: perimembranous (A), muscular posteroinferior rim (B), doubly committed and juxta-arterial (C) and atrioventricular septal defect (D). The yellow lines show the septomarginal trabeculation.

Figure 7:

Aortic valve overriding the ventricular septal defect, with unequal leaflet sizes: the right coronary leaflet > the non-coronary leaflet > the left coronary leaflet.