Figure 18.2 represents variations of truncus arteriosus with interrupted aortic arch based on a multi-institutional study of 50 neonates in an effort to better define the morphology and characteristics of this particular anomaly. A modified version of the Collett and Edwards classification was established by Konstantinov and colleagues. In cases of aortic arch interruption, type B is the most common form of interruption. In the Van Praagh classification system, type IV truncus arteriosus includes interruption of the aortic arch, with the descending aorta supplied by the patent ductus arteriosus. In this subset of patients, the other pulmonary artery is supplied via the ductus arteriosus or an aortopulmonary collateral vessel. In the Van Praagh classification system, type III truncus arteriosus includes patients with origin of one pulmonary artery from the truncus. Among both groups A and B, the four subgroups are the same (see Fig. Van Praagh later developed a classification based on truncus patients with a VSD (group A) and those without (group B ). This type of truncus arteriosus is considered to be a form of pulmonary atresia with VSD. In type IV, no true pulmonary arteries are present and pulmonary blood flow is supplied via aortopulmonary collateral vessels. In type III, each pulmonary artery arises independently from the lateral aspects of the truncal root. In type II, each pulmonary artery originates from a separate origin off the posterior aspect of the truncal root. In type I, the main pulmonary artery arises from the truncal root and bifurcates into a right and a left pulmonary artery. Collett and Edwards first established four different anatomic classifications of truncus arteriosus based on the origin of the pulmonary arteries ( Fig. 18.1). The anatomic description of truncus arteriosus consists of an outlet ventricular septal defect (VSD), a single semilunar valve, and a common great artery that overrides the VSD. Truncus arteriosus occurs within the first 3 to 4 weeks of fetal life when there is failure of the aorticopulmonary septum to form and spiral within the embryonic truncus arteriosus, preventing a partition between the two great arteries.
Accurate noninvasive imaging is critical to defining the cardiac anatomy, guiding appropriate surgical management, and following these patients in the long term. Most cases are sent to surgery based on echocardiographic imaging alone. Truncus arteriosus is typically fatal without intervention in early infancy however, with current surgical therapy most children with truncus arteriosus survive. It occurs in 1% to 4% of all cases of congenital heart disease. Persistent truncus arteriosus is a rare congenital heart defect in which the aortic arch, pulmonary arteries, and coronary arteries arise from a common great artery originating from the base of the heart.
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