Truncus Arteriosus

Transposition of the great vessels is a type of congenital heart defect involving an abnormal arrangement of any of the great vessels such as the superior vena cava, pulmonary arteries and aorta. Congenital heart diseases concerning the primary arteries are further divided into sub-group called transposition of great arteries. There are different forms of anomalies like Dextro-transposition, Levo-transposition and Dextrocardia. It was first announced about two centuries ago, but the treatment became effective from the mid 21st century. Today the survival rate for infants is greater than 90%.

This is the case of 28 year-old adult with suspected congenital heart disease since birth, not treated in childhood at the his family's choice. At 27 years old, he was diagnosed with pulmonary atresia with ventricular septal defect and systemic-pulmonary collaterals, where surgery was contraindicated. A new review in our department showed that it was an atypical form of truncus arteriosus. The fact that a common arterial trunk with left-right shunt was viewed by echocardiography was a crucial fact for the indication of new catheterization, opening the prospect of surgical correction. Currently, the patient is well, with 7 years of postoperative outcome.

The normal development of the ventricular outlets and proximal region of the great arteries is a controversial subject. It is known that the conus, truncus arteriosus (truncus), and aortic sac participate; however, there are some doubts as to the actual prospective fate of the truncus. Some authors propose that it gives origin to the proximal region of the great arteries and that the myocardial cells of its wall become smooth muscle. Nevertheless, others think that the truncus only forms the arterial valve apparatus and that therefore the myocardial cells transform into fibroblasts. As a first approach to beginning to elucidate which process occurs, the aim of this article was to study the histological changes in the wall of these components of the developing heart in chick embryos whose hearts had been labeled at the truncoconal boundary at stage 22HH, tracing the changes up to stage 36HH. Also, the histological constitution of the wall of the pulmonary arterial trunk and its valve apparatus were studied in the posthatching and adult hearts of chickens and rats. The conus and truncus walls were always encircled by a myocardial sleeve from the outset of their development. Between stages 26HH to 28HH, the truncal myocardial cells adjacent to the mesenchymal tissue of the ridges began to lose cell-to-cell contacts and invaded the extracellular matrix. At stage 24HH, the aortic sac began to project into the pericardial cavity and became divided into two channels by the aortic-pulmonary septum at stage 26HH. The wall of the aortic sac is mostly constituted by a compact mesenchymal tissue. Initially, it does not have smooth muscle but this starts to appear at stage 30HH. The insertion ring of the valves, a broad structure, was formed by mesenchymal tissue. Both structures were always covered by a myocardial sleeve. The leaflets developed from the truncal ridges, the segment immediately proximal to the aortic sac. Our results indicate that the proximal region of the pulmonary and aortic arteries do not originate from the truncus arteriosus; rather, we found that they take origin from the aortic sac. Thus, our findings agree with the proposal that the myocardial cells of the external sleeve of the truncus become fibroblastic and suggest that the insertion ring of the arterial valves has a dual origin: fibroblasts produced by truncal myocardial transdiferentiation and the mesenchymal tissue of the proximal region of the truncal ridges, while the leaflets have their origin from the truncal ridges. We discuss the fact that, because the truncus arteriosus does not give origin to the trunks of the aortic and pulmonary arteries, it may be necessary to modify terminology. Based on our results, together with the new findings obtained by in vivo labeling, immunostaining, a chimeric approach, and ultrastructural studies, we propose a developmental model that correlates the fate of the conus, truncus, and aortic sac with the normal morphogenesis of the ventricular outlet tracts and the trunks of the great arteries.

Background. Repair of truncus arteriosus communis (TAC) in the neonatal and early infant period has become a standard practice. We report our experience on primary repair of TAC with a bovine pericardial-valved woven Dacron conduit as an alternative procedure to homografts, with a focus on early and midterm results. Methods. From January 2001 to December 2007, 15 patients with mean age 1.5 years (range 3 months to 8 years), underwent primary repair of simple TAC. Cases with cardiogenic shock, complex-associated cardiac lesions, or adverse anatomy of the truncal valve were excluded. The Collett and Edwards anatomical type classification of TAC was as follows: type I, 13 (87%); and type II, 2 (13%). Right ventricular outflow tract was reconstructed in all the cases with a bovine pericardial-valved woven Dacron conduit. Results. Overall mortality was 6.6% (1 death due to severe pulmonary hypertension). At a mean follow-up of 31 months (range 6-51), there were no deaths (5-year actuarial survival 93.4%). Out of the 14 midterm survivors, three developed stenosis of the pericardial-valved woven Dacron conduit, but only one underwent interventional procedure including percutaneous balloon dilation with stenting for associated left pulmonary artery hypoplasia. The rate of patients with no surgical or percutaneous reinterventions performed because of obstruction of the right ventricular outflow tract reconstruction in the midterm (5 years) was 86%. Conclusions. Truncus arteriosus communis repair with a bovine pericardial-valved woven Dacron conduit can be performed with a very low perioperative mortality and satisfactory midterm morbidity, favorably compared with that reported for the use of homografts. Interventional cardiac catheterization may delay the time of reoperation for inevitable conduit replacement due to stenosis.

Objective: A common arterial trunk is a solitary trunk that exits the heart through a common ventriculo-arterial junction and supplies directly the systemic, pulmonary, and coronary arterial pathways. It remains to be determined, however, how best to subclassify those hearts fulfilling this definition. The time-honored classification is based on the morphology of the pulmonary arteries, but an alternative approach also places emphasis on the nature of the systemic pathways. We evaluated our experience to establish whether these different approaches can be reconciled.