Authors: M. Barbic, MD AND M. Gangadharan, MD, FAAP, FASA - Children’s Memorial Hermann Hospital, University of Texas Health Science Center, Houston, TX
An echocardiogram obtained on a 26-hour-old, full-term girl due to differential cyanosis and suspected congenital heart disease demonstrates an interrupted aortic arch. Which of the following subtypes of interrupted aortic arch is MOST likely in this patient?
EXPLANATION
Interrupted aortic arch (IAA) is a rare, ductal-dependent, congenital cardiac anomaly with an incidence of about 0.03 to 0.19 per 10,000 live births and constitutes 1-5% of congenital heart diseases. It is characterized by a disruption in the lumen of the aortic arch at various sites between the ascending and descending aorta.
Classification of IAA is based on the site of the interruption. Type A interruption occurs distal to the left subclavian artery and is the second most common type, representing 10-20 % of cases. Type B interruption occurs between the left carotid and left subclavian artery. It is the most common type of IAA, representing 70-80% of cases (Figure 1). Type C is the least common type, representing less than 5% of cases, and occurs between the innominate and left carotid artery. Over 70% of Type B interruptions are associated with deletion of chromosome 22q11. The most commonly associated cardiac abnormalities are a ventricular septal defect (VSD), a bicuspid aortic valve, and an aberrant right subclavian artery arising from the descending aorta. The VSD is typically posteriorly malaligned and can result in left ventricular outflow tract obstruction. Perfusion distal to the interruption is critically dependent on a patent ductus arteriosus (PDA). Ductal closure will lead to lower body hypoperfusion, severe metabolic acidosis, and multiorgan failure. Differential cyanosis, with lower pedal oxygen saturation, may or may not be present depending on the degree of mixing at the level of the VSD. The ratio of pulmonary vascular resistance to systemic vascular resistance will determine the direction of flow across the PDA.
Prenatal diagnosis of IAA by ultrasound is possible in more than 50% of patients. The advantage of prenatal diagnosis is that treatment with prostaglandin E1 (PGE1) will begin immediately after birth. When the diagnosis is not made before birth, most patients will present with signs of cardiogenic shock after spontaneous closure of the PDA. Patients often present with end-organ dysfunction, such as necrotizing enterocolitis, liver and kidney dysfunction, and coagulopathy. Physical exam findings include lethargy, delayed capillary refill, cool skin, decreased peripheral pulses, and hypotension. Transthoracic echocardiography is usually adequate to delineate the anatomy of the aortic interruption, the patency of the PDA, the location of arch vessels, characteristics of the VSD, LV size and function, LVOT morphology, and size of aortic valve. A three-dimensional volume-rendered computed tomography angiogram may be obtained if further anatomic clarification is required. In extremely rare instances, in which the ductus arteriosus remains patent and collateral arterial vessels develop, patients may survive to adulthood before diagnosis.
Primary single-stage surgical repair is usually performed in the neonatal period after medical stabilization in the intensive care unit. The goals of medical management are maintenance of ductal patency with intravenous PGE1, avoiding decreases in pulmonary vascular resistance by minimizing fractional inspired oxygen concentration (FiO2), and maintaining cardiac output with inotropic agents, if needed, and balancing the ratio of pulmonary and systemic blood flow. The surgical repair consists of augmentation of the arch with graft material, if necessary, and anastomosis of the ascending and descending aorta to re-establish luminal continuity. Cardiopulmonary bypass may involve arterial cannulation through the ascending aorta or innominate artery for cerebral perfusion and the PDA for distal perfusion of the lower body. Selective cerebral perfusion or deep hypothermic circulatory arrest may be employed during arch repair. Early postoperative complications include bleeding, recurrent laryngeal nerve and phrenic nerve injury, and acute kidney injury. Late postoperative complications include aortic arch obstruction, LVOTO, and obstruction of the left main bronchus. Hybrid palliation with bilateral pulmonary artery bands and ductal stenting is an option when complete primary correction is not possible, such as prematurity or contraindications to cardiopulmonary bypass. Patients with IAA need lifelong follow-up by a cardiologist and for associated comorbidities. About 20-30% of patients will need repeat interventions in the cardiac catheterization suite or the cardiac operating room.
The correct answer is Type B, which is the most common type of IAA, representing 70 to 80% of cases of IAA. Type A is the second most common (10-20%), and Type C is the least common (<5%).
REFERENCES
Burbano-Vera N, Zaleski KL, Latham GJ, Nasr VG. Perioperative and Anesthetic Considerations in Interrupted Aortic Arch. Semin Cardiothorac Vasc Anesthesia. 2018;22(3):270-277. doi:10.1177/1089253218775954
LaPar DJ, Baird CW. Surgical Considerations in Interrupted Aortic Arch. Semin Cardiothorac Vasc Anesth. 2018;22(3):278-284. doi: 10.1177/1089253218776664.
Boutaleb AM, Tabat M, Mekouar Y, Bennani G, Drighil A, Habbal R. Rare case series of adult interrupted aortic arch. J Cardiol Cases. 2023;28(5):206-209. doi:10.1016/j.jccase.2023.07.004
