Definition of conotruncal anomalies

Abstract

Conotruncal anomalies are malformations of the infundibulum (conus arteriosus) and great arteries (truncus arteriosus) that have abnormal ventriculo-arterial alignments and connections: tetralogy of Fallot, truncus arteriosus, interrupted aortic arch type B, transposition of the great arteries, double-outlet right ventricle, double-outlet left ventricle, anatomically corrected malposition of the great arteries. Normally related great arteries have complete right-left (R-L) asymmetry in the development and anatomy of the subarterial conal free walls, with involution of the subaortic conal free wall musculature and good growth and expansion of the subpulmonary conal free wall musculature. All conotruncal anomalies lack this type of complete R-L conal free wall asymmetry. Solitus normally related great arteries (SNRGA) result from involution of the rightsided subaortic conal free wall and from simultaneous good growth and expansion of the left-sided subpulmonary conal free wall. Briefly, SNRGA=OR+4L. The rightsided subaortic conal free wall muscular development is grade 0 (absent) and the leftsided subpulmonary conal free wall muscular development is grade 4 (normal). This is how the embryonic aortic switch is normally performed. The left-sided PA is carried superiorly, anteriorly, and rightward above the RV, away from the interventricular foramen, atop the developing subpulmonary conal free wall. Simultaneously, the right-sided Ao moves inferiorly, posteriorly, and leftward because the subaortic conal free wall is undergoing involution, thought to be due to apoptosis. Consequently, the aorta passes mostly through the interventricular foramen and normally comes into direct fibrous continuity with the developing mitral valve (MV), above the morphologically left ventricle (LV), thereby accomplishing the normal embryonic aortic switch. Eleven normal and abnormal developmental and anatomic conotruncal equations are presented in this chapter. From an evolutionary perspective, the conotruncal anomalies appear to represent physiologically unsuccessful attempts to perform the embryonic aortic switch. Conotruncal anomalies are infundibular malformations, causing the great arteries to be abnormally connected, abnormally aligned, and abnormally related in space. To summarize, the evolution of complete R-L asymmetry in the development of the subarterial conal free walls made possible the embryonic aortic switch. This in turn led to the development of solitus normally related great arteries: SNRGA A =OR+4L. Its mirror-image isomer is: INRGA=4R+0L. Any other pattern of conal development results in a conotruncal malformation.