Common Arterial Trunk in a 3-Day-Old Alpaca Cria

Abstract

A 3-day-old alpaca cria presented for progressive weakness and dyspnea since birth. Complete bloodwork, thoracic radiographs, and endoscopic examination of the nasal passages and distal trachea revealed no significant findings. Echocardiogram and contrast study revealed a single artery overriding a large ventricular septal defect (VSD). A small atrial septal defect or patent foramen ovale was also noted. Color flow Doppler and an agitated saline contrast study revealed bidirectional but primarily right to left flow through the VSD and bidirectional shunting through the atrial defect. Differential diagnosis based on echocardiographic findings included common arterial trunk, Tetralogy of Fallot, and pulmonary atresia with a VSD. Postmortem examination revealed a large common arterial trunk with a quadricuspid valve overriding a VSD. Additionally, defect in the atrial septum was determined to be a patent foramen ovale. A single pulmonary trunk arose from the common arterial trunk and bifurcated to the left and right pulmonary artery, consistent with a Collet and Edwards' type I common arterial trunk with aortic predominance. Although uncommon, congenital cardiac defects should be considered in animals presenting with clinical signs of hypoxemia, dyspnea, or failure to thrive.

Figure 1

Thoracic radiograph: left lateral thoracic view of the skeletally immature alpaca cria demonstrating mild loss of the cranial waist, distention of the caudal vena cava, and a mild diffuse unstructured interstitial pattern in the lungs warranting cardiac evaluation. A reduced cervical tracheal diameter is also evident.

Figure 2

Two-dimensional echocardiographic images. (a) Right parasternal long axis view. Note the truncus arteriosus overriding the ventricular septal defect (star). (b) Right parasternal short axis view at the level of the heart base. Note the ventricular septal defect (star), atrial septal defect (asterisk), and lack of an obvious right ventricular outflow tract. LA, left atrium; RA, right atrium; RV, right ventricle; TA, truncus arteriosus.

Figure 3

Two-dimensional echocardiographic images of agitated saline contrast study. Two-dimensional echocardiographic right parasternal image of an agitated saline contrast study demonstrating primarily right to left flow of bubbles across the large ventricular septal defect. LV, left ventricle; RV, right ventricle; TA, truncus arteriosus.