Heterotaxy Syndrome in a Pediatric Cardiac Patient: A Case Report of Rare, Complex Congenital Heart Defects
Authors: Petrone Ashley Brooke , Koenig Zack , Rosen David , Verhoeven Alex 
Published: April 2020

BackgroundHeterotaxy syndrome, or situs ambiguous, is a multitude of thoracoabdominal congenital irregularities involving organ rearrangements across the body axis. The array of symptoms can be subdivided into either left or right isomerism, which conventionally refers to the anatomy of the designated side presenting bilaterally. While there have been approximately 266 case reports published on heterotaxy syndrome to date, no case report has documented the combination of symptoms seen in our patient, who presents with defects characteristic of both left and right isomerism.PresentationA male infant was delivered early at gestational age 37 weeks and 3 days, due to poor fetal growth. Fetal echocardiogram had been performed prior to delivery and was indicative of complex congenital heart defects, specifically heterotaxy syndrome with dextrocardia, double‐outlet right ventricle with transposed great arteries, a complete atrioventricular canal defect, a large ventricular septal defect and a large common atrium. The suspected defects were confirmed after delivery via echocardiography and cardiac catheterization. Given that heterotaxy can occur by itself or as a secondary feature of another genetic disorder, karyotyping via chromosomal array and chromosomal analysis were performed; however, no chromosomal or genetic abnormalities were identified.Results – Anatomical Features

‐Mirror image dextrocardia with the inferior vena cava and descending aorta located to the left of the spine at the level of the diaphragm
‐There is both a large septum primum and septum secundum defect, which gives rise to essentially a single common atrium, with unrestricted flow across the atrium. The anatomic right atrium is on the patient left, and the anatomic left atrium is on the patient right
‐There are bilateral superior vena cava draining into the anatomic right side of the common atrium is on the patient left. All four pulmonary veins drain into the anatomic left atrium on the patient right. There is also anomalous drainage of the inferior vena cava into the anatomic left atrium is on the patient right
‐The anatomic right ventricular on the patient left gives rise to both the aorta and main pulmonary artery – double‐outlet right ventricle. There is also is transposition of the aorta and main pulmonary artery
‐There is a complete atrioventricular defect with a single common atrioventricular valve with few chordae tendinae attached to the ventricular septum
‐There is severe pulmonary valve stenosis with no appreciable regurgitation. There is no aortic valve stenosis or regurgitation, and the aortic valve is appropriately tri‐leafletConclusionThis form of heterotaxy syndrome partially matches both right and left atrial isomerism. Double‐outlet right ventricle, malposition of the great vessels, and pulmonary and subpulmonary stenosis are typical of right atrial isomerism. In contrast, the common atrioventricular canal defect, bilateral superior vena cava, and anomalous drainage of the inferior vena cava hint at left atrial isomerism. This anatomical case reports highlights the complexity of heart development and highlights the complexity of surgical and long‐term clinical management of heterotaxy syndrome.Cardiac catheterization visualization of dextrocardia and bilateral superior vena cava draining into patients left‐side of common atriumFigure 1Echocardiography visualization of common atrium with small intact septum (yellow arrow), common atrioventricular valve (red arrow), and ventricular septal defect (purple asterisk)Figure 2