Development and maldevelopment of the ventricular outflow tracts

Abstract

In this chapter, we provide an account of cardiac development that, hopefully, will underscore the understanding of the surgical anatomy of the lesions to be contained within the overall book. The book alleges coverage of the surgical treatment of "conotruncal anomalies". It is our belief that one of the lesions to be considered, namely congenitally correct transposition, requires abnormal looping of the developing heart tube as the primary abnormal developmental event. To put this lesion into context, therefore, we begin our account with a brief review of formation and looping of the heart tube. We then concentrate on the normal and abnormal development of the ventricular outflow tracts, although we question whether development is best considered in terms of the "conus" as opposed to the "truncus". It is anatomically more accurate to address development of the outflow tract in terms of its proximal, intermediate, and distal components, and to consider these intrapericardial parts separately from the extrapericardial arterial pathways, which develop within the pharyngeal mesenchyme. The tripartite approach to development then permits rational explanations to be provided for formation of the ventricular outflow tract, the arterial valves and their supporting sinuses, and the intrapericardial arterial trunks. This approach to normal development permits analyses to be made of the lesions afflicting the different components, such as aortopulmonary windows, common arterial trunk, arterial valvar malformations, tetralogy of Fallot, double outlet right ventricle, and discordant ventriculo-arterial connections.