Cardiovascular manifestations of heterotaxy and related situs abnormalities assessed with CT angiography

Abstract

Heterotaxy and situs abnormalities describe an abnormal arrangement of visceral organs in the thoracoabdominal cavity across the normal left-right axis of the body. It is associated with a high occurrence of congenital heart and abdominal defects, including anomalous pulmonary venous connections, systemic venous abnormalities, asplenia, and intestinal malrotation. Without proper diagnosis and surgical intervention, the prognosis of patients with heterotaxy syndrome and associated congenital defects is extremely poor. Complex intracardiac and extracardiac lesions are common in heterotaxy and can be difficult to assess by echocardiography. CT angiography (CTA) is a useful tool in this setting to accurately assess intracardiac and extracardiac abnormalities in this population for medical or surgical management. The intention of this pictorial essay is to review the most common cardiovascular defects involved with heterotaxy syndrome in addition to emphasizing the utility of CTA in the identification and classification of anomalies seen in these patients. This review briefly defines most common terminology used in situs abnormalities as well as presents CT images and 3-dimensional reconstructions of common anomalies associated with situs abnormalities. In summary, this review should prepare radiologists and pediatric cardiologists to describe heterotaxy and situs abnormalities in addition to recognizing the utility of CTA in these patients.

Keywords: CT angiography; Heterotaxy; Isomerism; Situs abnormalities; Situs ambiguus; Situs inversus.

Fig. 1

CTA images of atrial appendage anatomy in a healthy child with situs solitus. (A and B) Images are 3D volume-rendered reconstructions viewed from a right and left anterolateral position, respectively. (A) The right-sided morphologically RAA is shown, which is broad based and triangular. (B) A left-sided morphologically LAA is shown, which is narrow and finger-like. (C) This oblique coronal image shows a normal RAA. Note that the pectinate muscles extend into the body of the atrium. (D) This oblique transverse image shows a normal LAA, with narrow, smooth-walled neck. A, anterior, CTA, CT angiography; F, feet; H, head; L, left; LAA, left atrial appendage; P, posterior; R, right; RAA, right atrial appendage; 3D, 3-dimensional.

Fig. 2

The relationship of the bronchus to its ipsilateral pulmonary artery can be useful in determining situs. These images are 3D volume-rendered CTA reconstructions in 4 different patients. Each image shows the airway (pink) and the RPA and LPA. (A) This image shows this relationship in a patient with situs solitus. The right bronchus is eparterial; the bronchus branches superior to the first lobar division of the pulmonary artery. The left bronchus is hyparterial; the bronchus branches inferior to the first lobar division of the pulmonary artery. (B) The relationship of the bronchi and the pulmonary arteries RPA and LPA of a patient with situs inversus is shown. The right-sided bronchus is hyparterial, consistent with a morphologic left bronchus, whereas the left-sided bronchus eparterial is consistent with a morphologic right bronchus. (C) This image shows a patient with right isomerism. Both bronchi are eparterial. (D) This image is from a patient with left isomerism, showing bilateral hyparterial bronchi. CTA, CT angiography; F, feet; H, head; L, left; LPA, left pulmonary artery; R, right; RPA, right pulmonary artery; 3D, 3-dimensional.

Fig. 3

The tracheobronchial tree anatomy can also be valuable in determining situs. These images are 3D volume-rendered reconstruction of the airways in 4 different patients. (A) This image shows the airways of the patient with situs solitus. The right-sided bronchus is short and horizontal compared with the left-sided bronchus. (B) The tracheobronchial tree of a patient with situs inversus is shown. The right-sided bronchus is long and angled, consistent with a morphologic left bronchus, whereas the left-sided bronchus is shorter and less angled, consistent with a morphologic right bronchus. (C) This image shows a patient with right isomerism. Both bronchi are short and horizontal. This patient has tri-lobed lungs bilaterally. (D) This image, from a patient with left isomerism, shows long and angled bilateral bronchi. This patient has bi-lobed lungs bilaterally. F, feet; H, head; L, left; R, right; 3D, 3-dimensional.

Fig. 4

This CTA demonstrates the anatomy in a child with situs inversus, along with congenitally corrected transposition. (A and B) These 3D volume-rendered reconstructions are viewed from a right and left anterolateral position, respectively. In contrast to Figure 1, image A shows a narrow, finger-like morphologically LAA on the right side of the thorax. A RSVC is seen coursing anterior to the LPVs and entering the CS. (B) Abroad based, triangular morphologically RAA lateralized to the left is shown. A LSVC is seen entering the left-sided atrium. (C) This transverse image shows a morphologically LAA on the right side of the heart. Note that the pectinate muscles are confined to the tip of the appendage. The LPV is seen entering the morphologic left atrium. (D) This maximum-intensity projection image is viewed in an oblique coronal plane. It shows a RAA, with pectinate muscles extending into the body of the atrium, on the left. The RSVC is seen entering the CS, which courses inferior–posterior to the morphologic LA to enter the morphologic RA. A left-sided IVC also enters the morphologic RA. CS, coronary sinus; CTA, CT angiography; F, feet; H, head; IVC, inferior vena cava; L, left; LA, left atrium; LAA, left atrial appendage; LPV, left pulmonary vein; LSVC, left superior vena cava; P, posterior; R, right; RA, right atrium; RAA, right atrial appendage; RSVC, right superior vena cava; 3D, 3-dimensional.

Fig. 5

This is a CTA in a neonate with right isomerism. (A and B) These 3D volume-rendered reconstructions are viewed from a right and left anterolateral position, respectively. The atrial appendages (*) look similar and show characteristics of a morphologic right atrial appendage. They are both broad-based, triangular structures. This patient also has bilateral RSVC and LSVC. Patients with right isomerism will often have pulmonary venous abnormalities. (C) This maximum intensity projection image in the coronal plane shows the pulmonary veins in this patient connecting to a PVC behind the atria and draining via a VV that dives below the diaphragm. Note the large, central liver. (D) This oblique coronal plane shows 2 broad appendages (*) that wrap anteriorly on either side of the AO. AO, aorta; CTA, CT angiography; F, feet; H, head; LSVC, left superior vena cava; PVC, pulmonary venous confluence; RSVC, right superior vena cava; VV, vertical vein.

Fig. 6

This is another neonate with right isomerism. (A) This 3D volume-rendered reconstruction is viewed from behind to show mixed, supracardiac totally anomalous pulmonary venous return. The RLPV (arrow) and LPV (arrows) drain into the LSVC. The RUPV (arrow) drains into the RSVC. (B) This maximum intensity projection image is viewed in an oblique coronal plane. The RSVC drains into the RSA. The LSVC drains into the LSA. F, feet; H, head; L, left; LPV, left pulmonary vein; LSA, left-sided atrium; LSVC, left superior vena cava; R, right; RLPV, right lower pulmonary vein; RSA, right-sided atrium; RSVC, right superior vena cava; RUPV, right upper pulmonary vein.

Fig. 7

This is a CTA in a neonate with left isomerism. (A and B) These 3D volume-rendered reconstructions are viewed from a right and left anterolateral position, respectively. (C and D) These sagittal images are through the right-sided and left-sided atrial appendages, respectively. The appendages (*) look similar and show characteristics of a morphologic left atrial appendage. They are narrow, finger-like structures. A, anterior; CTA, CT angiography; F, feet; H, head; P, posterior.

Fig. 8

These images are from another child with left atrial isomerism. (A) This image is an oblique coronal plane. Similar to the prior figure, the appendages (*) are narrow and finger-like. (B) This image is a maximum intensity projection image in a transverse plane. It shows a common atrium with a pulmonary venous anomaly frequently present in left isomerism: the RUPV and LUPV drain separately to the ipsilateral side of the common atrium. (C) This image is a transverse plane. An enlarged AV is seen posterior and rightward to the AO, consistent with an interrupted inferior vena cava. (D) This maximum intensity projection image in a sagittal plane shows the enlarged AV that drains into the SVC. The right pulmonary artery has been connected to the SVC, consistent with the history of a Glenn procedure. A, anterior; AO, aorta; AV, azygous vein; CTA, CT angiography; F, feet; H, head; L, left; LUPV, left upper pulmonary vein; P, posterior; R, right; RUPV, right upper pulmonary vein; SVC, superior vena cava.