Three-dimensional images of a pulmonary dominant truncus arteriosus before and after a novel repair

This paper documents, for the first time, the in vivo size, geometry, and function of the different components of this important subtype of truncus arteriosus (pulmonary dominant). Previous descriptions were based on examining formalin-fixed (collapsed) specimens, or descriptions during operations. It is hoped that this information can be of value in designing operative treatment as well as interpreting future sequential imaging, with the aim of optimizing the results of comprehensive repair.


INTRODUCTION
Truncus arteriosus (TA) is a complex congenital anomaly characterized by the presence of a single arterial outlet from the heart, which gives origin directly to the systemic, pulmonary, and coronary circulations. The condition has been repeatedly classified by Collett and Edwards, 1 Van Praagh, 2 and more recently by Robert Anderson and colleagues. 3 The latest classification described two types, aortic or pulmonary dominance. The latter corresponded to TA with interrupted aortic arch in previous classifications. 1,2 We present detailed pre-and post-repair (using a novel technique) 3D images of all the component parts of a pulmonary dominant truncus arteriosus.

PATIENT AND METHODS
A 1-year-old female patient presented to Aswan Heart Centre with the clinical and echo diagnosis of truncus arteriosus.
The details of the novel repair technique will be the subject of future communication. In short, the technique consists of transection of the arterial trunk above and below the origin of the pulmonary arteries, wide mobilization of the latter, creation of an autologous neo-right ventricular outflow tract (RVOT), and importantly, tailoring each component, with the aim of restoring the pattern of flow in the heart. 4

Ventricular size, shape, and function
Pre-operatively, the uncorrected truncus arteriosus results in a very large left-to-right shunt through the unrestrictive ventricular septal defect (VSD) as well as the communication between the trunk vessel and the pulmonary arteries. This results in much dilatation and hypertrophy of both ventricles ( Figure 1). Post-operatively, separation of the systemic from the pulmonary circulation results in a considerable diminution of the volumes of both ventricles (Figure 1). This is accompanied by changes in instantaneous end-systolic and end-diastolic volumes during the cardiac cycle; as well as ejection fraction 5,6 ( Figure 2). These changes resulted in partial normalization of these parameters. 5 Origin of the arterial trunk from the ventricles Before operating, the arterial trunk originated from both ventricles through a very large ventriculoarterial connection (Figure 3). Post-operatively, the neo-aorta arose from the left ventricle with a smaller normal-looking (Flask-shaped) neo-aortic root. The pulmonary artery is now connected to the right ventricle by a neo-RVOT as well as a 14 mm Contegra (Medtronic, Dublin, Ireland) valve with a preserved angle of pulmonary artery bifurcation (Figures 4 and 5).

Coronary arterial origin and distribution
Pre-operatively, the right coronary artery arose from above the anterior sinus of the ventriculoarterial valve, while the left coronary artery arose from the posterior sinus ( Figure 3). Postoperatively, the two coronaries arose from the anterior and posterior neo-aortic sinuses respectively (Figure 3).

Mode of origin and communication of the great arteries
Before operating, the systemic vessel arose from the dominant pulmonary arterial trunk below the origin of the brachiocephalic artery with a slightly hypoplastic aortic arch (Figure 4). In addition, a five mm patent ductus in the region of the ''isthmus'' followed by slight dilatation of the descending aorta. After operating, there was a separation of the systemic from the pulmonary circulation with the tailoring of the neo-ascending aorta, division of the ductus, and refashioning of a neo-RVOT. The pulmonary artery is now connected to the right ventricle by a neo-RVOT as well as a 12 mm Contegra (Medtronic, Dublin, Ireland) valve with a preserved angle of pulmonary artery bifurcation.  Overall appearance This figure ( Figure 5) shows all the changes in the individual components of the TA including the topology of the great articles, and the normal-like crossing appearance.

Comments and future direction
This paper documents, for the first time, the in vivo size, geometry, and function of the different components of this important subtype of TA. Previous descriptions were based on examining formalin-fixed (collapsed) specimens or descriptions during operations. It is hoped that this information can be of value in designing operative treatment as well as interpreting future sequential imaging, with the aim of optimizing the results of comprehensive repair.