Abstract 15341: Persistent Fifth Arch as an Aortopulmonary Connection in a Case of Tetralogy of Fallot

Abstract

Persistent fifth aortic arch is a heterogeneous vascular anomaly with variable anatomical presentations and physiological consequences. This unusual embryological remnant represents a management challenge, particularly in critical right sided obstructive heart lesions where accurate delineation of sources of pulmonary blood flow is essential. This is a newborn 2 kg premature male born at 34 weeks of gestation with prenatally diagnosed tetralogy of Fallot. Post-natal echocardiogram confirmed diagnosis with evidence of moderate-to-severe pulmonary stenosis, restrictive ventricular septal defect, and a right aortic arch. CT angiogram ordered to delineate the head and neck vessel anatomy showed an exceedingly rare finding of an isolated connection of the left subclavian artery (LSCA) to the main pulmonary artery (MPA) via a left sided ductus arteriosus. Blood flowed from the common carotid arteries, through the circle of Willis, and, in a retrograde direction, into the LSCA. Prostaglandin E was initiated due to concern for ductal dependent pulmonary blood flow, but after clinical observation it was discontinued without subsequent onset of cyanosis. Repeat echocardiograms were reassuring in showing persistence of the left ductus arteriosus. The patient was discharged home at 5 weeks-old and at 4 months-old he underwent complete repair after developing progressive desaturations and worsening sub-valvar and valvar pulmonary stenosis. The surgical repair included ventricular septal defect closure, transannular patch, extensive right ventricular myomectomy and reimplantation of LSCA onto the left common carotid artery. The post-operative course was uncomplicated. This rare case of persistent fifth aortic arch with retrograde flow to the LSCA demonstrates the complementary roles of noninvasive imaging modalities in guiding medical therapy and surgical management. This unusual blood flow pattern and initial concern for duct dependent pulmonary blood flow complicated early management, but a conservative approach with repeat imaging allowed for eventual complete repair.