arch anomalies

8/12/2019 Arch Anomalies

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The Radiology Assistant

Vascular Anomalies of Aorta, Pulmonary and Systemic vesselsby Marilyn J. Siegel and Robin Smithuis

Mallinckrodt Institute of Radiology, Washington University School of Medicine in St. Louis, USA and the Rijnland Hospital in Leiderdorp, the Netherlands

l Overview of Arch Anomalies

Embryologyl Aortic Arch Anomalies

Right Arch Mirror ImageRight Arch with Aberrant left subclavianDouble Aortic ArchLeft Arch Aberrant Right SCAInnominate artery compression syndromeAortic Coarctation

l Pulmonary Arterial anomaliesPulmonary agenesisPulmonary SlingPatent Ductus Arteriosus

l Pulmonary venous anomaliesPartial Anomalous Venous ReturnScimitar syndrome

l Systemic veins

Left Superior Vena CavaLeft Superior Intercostal Vein.Azygos Continuation of IVC

l Technique and Protocol

This review is based on a presentation by MarilynSiegel and was adapted and illustrated for theRadiology Assistantby Robin Smithuis.Marilyn Siegel is specialized in pediatric and chestradiology.The second edition of her book entitled Pediatric BodyCT will be out next week.

In this review we will discuss the most commonvascular anomalies of the aorta, pulmonary vesselsand systemic veins in the chest.Most of these anomalies are found in children, butsometimes they are discovered later in adulthood.Many of these anomalies are asymptomatic or 'leavealone' lesions, but some of these anomalies are

symptomatic and need to be treated.As a radiologist we have to be familiar with theseanomalies.

A simple mouse click on an item on the left will bringyou directly to this subject.

Publicationdate:1-11-2007

Overview of Arch Anomalies

1. Aberrant Right subclavian artery

Most common arch anomaly Not a true ring

Usually asymptomatic Sometimes dysphagia lusoria when dilated

suvclavian artery compresses esophagusposteriorly.

2. Innominate artery compression syndrome

In children the brachiocephalic (innominate)artery is located more to the left and maycompresses the trachea anteriorly.

3. Right Arch Mirror Image

Mirror-image variety of the left arch

Asymptomatic Associated congenital heart disease in 98%,

mostly tetralogy of Fallot.

4. Right Arch with Aberrant left subclavian

Left subclavian artery is the last branch. Obstructing anomaly.

5. Double Aortic Arch

Complete ring encircles esophagus and trachea Four vessel sign.

6. Double Arch with Atretic Segment

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First branch is the right common carotid,followed by the left carotid and the leftsubclavian artery. The last branch is the rightaberrant subclavian artery.

l Right Arch with aberrant left subclavian artery:

Mirror image of the left arch with aberrant rightsubclavian artery.

Left arch between the left subclavian and left

common carotid artery involutes. First branch is left common carotid, followed by

right carotid and right subclavian artery. Thelast branch is the left aberrant subclavianartery.

When you look at these illustrations, you have torealize, that these are views from above, while CT-images have a 'view from feet'.On a CT-image the ascending aorta will be on theupper part of the image and the descending aorta willbe on the lower part.

Aortic Arch Anomalies

Axial image and volume rendering posterior view

Right Arch Mirror Image

This is the mirror-image variety of the left arch.

On the left a 2 year old girl with wheezing andcoughing.Study the images and then continue.You have to realize, that axial CT-images are viewedfrom the feet, while the illustrations above are viewedfrom above

On the axial image there is a right archOn the volume rendered image there is mirror imagebranching of the brachiocephalic arteries, no aberrantsubclavian artery, so this is a right arch mirror image.

Mirror image aortic arch (yellow arrow) and a VSD (redarrow)

This anomaly is asymptomatic, because there is noobstructing ring.Almost all of these patients however come to ourattention because they have associated congenitalheart disease in 98% of cases.This patient had a mirror image aortic arch and aVSD.

On the left an adult who was operated in his childhoodfor a Tetralogy of Fallot (pulmonary stenosis, rightventricular hypertrophy, VSD, overriding aorta).At surgery the VSD was patched and the pulmonaryoutflow tract was enlarged.Notice that there is also a right arch.

In the United States there are now more than onemillion adults who have survived their congenital




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Mirror image aortic arch in patient operated for tetralogy ofFallot.

heart disease.In the ER you will see these patients because they ageand get chest pain like many adults do and so you willsee these anomalies more frequently.

Right Arch with Aberrant left subclavian

The Right Aortic Arch with an aberrant left subclavian

is an obstructing arch anomaly.The first branch of the aorta is the right commoncarotid, followed by the right subclavian artery andthe left common carotid.This also is a true ring.The ligamentum ductus arteriosus between the arch atthe level of the left subclavian artery and the leftpumonary artery completes the ring.If this ligament is very short, there will be a lot ofcompression.

View more images: 1/4


On the left a patient with a right arch with an aberrantleft subclavian (indicated by the yellow arrow).

Scroll through the images on the left.Again you have to realize that the axial CT-imageshave a 'view from feet'.

Which vessels are indicated by the yellow and greenarrow?

There is a right arch and the left subclavian artery isthe last branch of the aortic arch, indicating that thisis an aberrant left subclavian.Medially to the left subclavian artery we see the leftcommon carotid, that originates from the right sideand has an oblique course to the left.The yellow arrow indicates the azygos vein.The green arrow indicates the left superior intercostalvein, a normal variant, that we will discuss later.

Right Arch with Aberrant left subclavian (yellow arrow)

Same patient.Posterior oblique view of volume rendered image toshow the aberrant left subclavian artery.In a mirror type right arch, the left subclavian is thefirst brach and forms the left innominate together withthe left common carotid.

On the left images of a symptomatic child.On the axial image there is a right arch with the leftsubclavian artery that comes off on the posterior sideand runs behind the trachea and the esophagus.The compression of the trachea is demonstrated onthe volume rendered view.




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Double Aortic Arch

On the left a chest film of a 6-month old boy withstridor and cough.The trachea is deviated to the left, otherwise the chestfilm is normal.So there is some mass effect on the right side.

On the left the reconstructions demonstrating adouble aortic arch.There are branches coming off the right arch andbranches coming off the left arch.

Double Aortic Arch

The right arch is typically larger and higher than the

left.There is a complete ring that encircles the esophagusand the trachea and usually there is stridor ordysphagia.Two brachiocephalic arteries arise on each sideseparately (four vessel sign) and there is nobrachiocephalic artery.

On the left a chest film of a young adult with a cough.There is a right paratracheal mass.The differential diagnosis is tumor, adenopathy orvessel (right arch, dilated azygos vein, dilatedaberrant right subclavian artery).




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You should not confuse it for a right arch.The left arch is just very small and there is still a fourvessel sign.

Double Arch with Atretic Segment

On the left a dominant right arch and a small left arch.The atretic segment is marked by the arrow.Notice the four vessel sign.

On a posterior view the interruption is nicelydemonstrated.Remember that there is still a ring, so there is stillobstruction.

Another case on the left.Do not call this a right arch.It still is a double arch and there is a atretic fibroticsegment on the posterior side of the left arch, thatcompletes the ring.Notice the four vessel sign.




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Same patient.Always look at the airways.On the recoonstruction the impression on the tracheais better appreciated.

Aberrant Right SCA, no compression of the trachea

Left Arch Aberrant Right SCA

l Also known as arteria lusoria.l Most common arch anomaly.

l Not a true ringl Usually asymptomatic.On the left a young patient, who has a CT for anotherreason.

Study the images and then continue.Notice that there is a left arch, but the rightsubclavian artery is the last brachiocephalic artery tobranch off the arch.

Dysphagia lusoria in patient with dilated aberrant rightsubclavian artery.

Only rarely these patients become dysphagic(dysphagia lusoria) , when the origin of the rightsubclavian artery becomes dilated.On a barium study of the esophagus you will see aposterior impression with an oblique course directedtowards the right shoulder.

On the left a 78 year old woman with dysphagia.There is consolidation in the right upper lobe, maybe

due to aspiration.There is a dilated vessel that compresses theesophagus and it originates from the left-sided aorta,i.e. an aberrant right subclavian artery.

On the left the same patient with dilated aberrantright subclavian artery.Coronal reconstruction.




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Aortic Coarctation

l Narrowing at level of distal arch / descending aorta.l Chest film: 'figure 3' sign, inferior rib notching.

l Intervention when gradient > 20 mm Hg.l Associated with bicuspid aortic valve (75%), cerebral

aneurysms (5-10%) and Turner syndrome (20% havecoarctation)

On the left a 2 month old boy with heart failure.First study the image, then continue

The findings are:

l Large thymus which is normal for a 2 month old.

l Striking discrepancy between diameter of ascendingand descending aorta.

The diagnosis is coarctation, which is nicelydemonstrated on the posterior view of thereconstruction.

There are two types of coarctation.The type we usually see is the post-ductal type, whichis distal to the left subclavian artery.

The uncommon pre-ductal type is seen in neonates.They present with severe heart failure, mostly withinthe first week of life, usually on the first day.The occlusion is in front of the left subclavian.

First study the axial image followed by the sagittalreconstruction, then continue.

The findings are:

l Big internal mammarian arteries on the axial imagedue to a high grade stenosis as a result of a

coarctation. Probably could not make the diagnosisbased on the axial images alone.

l Post-ductal coartation only seen on sagittalreconstruction.

l Intercostal collaterals.

The intercostal collaterals typically occur between the3rd and the 8th rib.




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Intercostal collaterals in aortic coarctation

Pre-ductal type of coarctation

On the left two neonates with the pre-ductal type ofcoarctation.The stenosis is in front of the left subclavia and thereis arch hypoplasia.Collaterals do not occur, probably because they don't

have time to develop.

Coarctation treated with angioplasty (left) and stentplacement (right)

Coarctation is treated with angioplasty, stentplacement or patch aortoplasty.The image on the far left is the result after

angioplasty.Next to it a patient who was treated with a stent.

Notice that the stent is obstructing the orfice of theleft subclavian artery.

Pseudo-aneurysm in coarctation treated with stent-

On the far left a patient who was treated with a stent.The stent ruptured causing restenosis.Next to it two patients with pseudo-aneurysm.One after angioplasty and another who developed apseudo-aneurysm after stent placement.They have to be repaired because they will rupture.

Pseudo-aneurysms are seen in

l 10% after angioplasty.l 30% after patch aortoplasty.




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placement

Pulmonary Arterial anomalies

They most common anomalies of the pulmonaryarteries are listed in the table on the left.

Pulmonary agenesis on the right side

Pulmonary agenesis

l Also called congenital interruption of the pulmonaryartery.

l Unilateral absence of the pulmonary artery.l Small lung and hilum.l Compensatory hyperinflation of contralateral lung

with herniation.

On the left a young adult, who had cyanotic spells asa child.

She is now in good health and comes in for anotherreason.On the chest film the differential is atelectasis,pneumonia or maybe a tumor.The CT shows, that he right lung is not developed andthe space around the atresic pulmonary artery is filledwith fibrofatty tissue with collaterals.So this is pulmonary agenesis.If many collaterals develop there will also be somedevelopment of the lung.

Pulmonary agenesis on the left side

On the left another case of absent pulmonary arterywith absence of lung development.On the CT the left lung is absent.

These patients may be totally asymptomatic.

Pulmonary Sling

Pulmonary Sling

On the left a 4 month old girl with abnormal echo,benign heart murmur and no respiratory or feeding

difficulties.The sagittal reconstruction shows an anomalousvessel on the posterior side of the trachea.There is a little mass effect on the trachea.




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The cardiologists are not interested in the flowdirection, but just want to confirm the diagnosis.

Notice the connection between the pulmonary artery

and the descending aorta.

When the duct closes it may also calcify.This a normal variant.

Pulmonary venous anomalies

Partial Anomalous Venous Return

The most common features of Partial AnomalousVenous Return are listed in the table on the left.

The anomalous veins drain into the followingstructures:

l RUL: SVC association with sinus venosus-type ASD.

l RLL: IVC (usually), sometimes Portal or Hepatic vein.Can be isolated finding or combined with pulmonaryhypoplasia (Scimitar syndrome).

l LUL: Brachiocephalic vein (isolated finding).l LLL: rare (if you find a case publish it).

Right upper lobe anomalous venous returnOn the left a 2 month old, who is asymptomatic buthas a murmur on physical examination.




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Right upper love anomalous vein drains into the superiorvena cava.

There is a connection between the SVC and apulmonary vein, so this is an anomalous venousreturn.

Pulmonary hypertension in a patient with partiallyanomalous pulmonary venous return.

All these partially anomalous pulmonary venousreturns are left to right shunts, but when small, theyare clinically insignificant.When there is a significant shunt, they may cause(late) pulmonary hypertension as seen in the case on

the left.

The chest film in this adult shows large pulmonaryarteries and a large right atrium and ventricle as aresult of pulmonary hypertension.

Right upper lobe anomalous return (2)

On the left a patient with a murmur.Study the images and then continue.

l There is an anomalous return of the right upper lobeto the SVC.

l At a slightly inferior level there is also an ASD.l Contrast is seen going almost immediately into the

left atrium.l This type of ASD is called the sinus venosus-type

ASD.

On the left a similar case.Notice the anomalous return of the right upper lobevein into the VCS and the additional ASD at a lowerlevel.




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Right lower lobe anomalous return

On the left a right lower lobe anomalous return.The vein drains into the IVC.

The anomalous vein gently curves to the rightcardiophrenic angle and is shaped like a Turkish sword('Scimitar')

Right lower lobe anomalous venous return into the azygosvein.

On the left another right lower lobe anomalous return.The vein drains into the azygos vein.Upper lobe veins may also drain into the azygos vein.

On the left a 10 year old girl suspected of having

pneumonia.Study the images carefully, because there are threefindings and then continue reading.

The findings are:

l Small right lung due to hypoplasial Anomalous venous returnl Right aortic arch

This patient has a scimitar syndrome and also a rightarch.So the lesson is, that when you see one anomaly, lookfor another one.

Scimitar syndrome

The features in scimitar syndrome are listed in thetable on the left.




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Scimitar syndrome with a hypoplastic right lung.

On the left another patient with a scimitar syndrome.There is a hypoplastic right lung with mediastinal shiftand there is anomalous venous return.Notice that on the coronal MIP you can nicely see thedifference in vascularization of the lungs withhypovascularity on the right.


Left upper lobe anomalous venous return intobrachiocephalic vein.

Scroll through the images on the left.Notice how the left upper lobe vein runs from thehilum cranially into the brachiocephalic vein.

The differential diagnosis of a left upper lobeanomalous venous return into brachiocephalic veins isa left Superior Vena Cava (SVC).A left SVC however drains into the coronary sinus.

Systemic veins

Left Superior Vena Cava

l Represents persistent left common cardinal vein




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l Passes anterior to left main bronchus and drains intodilated coronary sinus

l 0.5% of general population and 5% of patients withcongenital heart disease

l Small Right SVC in 90% of cases


Describe the images on the left and then continuereading.

On the left side there is a vascular structure, that runsinferiorly below the level of the left hilum and entersinto a dilated coronary sinus.The diagnosis is left or double superior vena cava.

Left Superior Intercostal Vein

Left Superior Intercostal Vein.

This is an anastomosis between the accessoryhemiazygos vein and the left brachiocephalic vein.It courses along the lateral margin of the aortic arch('aortic nipple').It is a normal variant and if you look for this structureyou will frequently notice it.Catheters or pacemaker leads may course along leftside of mediastinum.

On the left a patient with a left superior intercostalvein.Notice the 'aortic nipple sign'.

Left Superior Intercostal Vein

On the left another example of a left superiorintercostal vein.It courses along the lateral margin of the aortic archfrom the the accessory hemiazygos vein to the leftbrachiocephalic vein.

Summary of left paramediastinal structures




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1. Left VCS:

from subclavian vein to coronary sinus2. Anomalous LUL pulmonary vein:

from left pulmonary hilum to brachiocephalicvein.

3. Left superior intercostal vein:

from accessory hemiazygos vein to leftbrachiocephalic vein.

Azygos Continuation of IVC

l Abcense of hepatic segment of IVC with azygoscontinuation.

l IVC interrupted above level of renal veins.l Association with congenital heart disease and

polysplenia.

Technique and Protocol

Ideally a 64 slice scanner is used, but even a 4-slicescanner will suffice for studying vascular anomalies.The technique for these anomalies in the chest is thesame as we use for pulmonary embolus detection.Thin collimation is used in combination with a fasttable speed in order to get the highest resolution withthe lowest radiation exposure.Usually a pitch of 1.5 is used.In children we preferably do not use thin collimation,because of the higher radiation exposure, but theseanomalies can be very small (voorbeeld dia 18), sothin collimation is necessary.

mAs and kVpIn a child with a weight of less than 10Kg 40mAs willwork in the chest.In children with a weight more than 45 Kg adultprotocols are used with 100 mAs or more.In small children under 50 kg you can decrease thekVp to 80 and that works very well in the chest.Remember in the chest there is inherent contrast fromthe lungs and by dropping the kVp you enhance thiscontrast.

On the left a 3-year old.

Non-breath hold images with 50mAs and 80 kVp on a16 row detector. Although the axial images are a littlebit grainy, the reconstructions are just fine.

Do these patients need sedation? Well most of thetime they don't.If you can get the patient on the table and they are




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relatively still, even if they are breathing, you will getgood studies.If you can't get the patient on the table, because theyprefer the floor, you've got to sedate.

In about 20-25% of pediatric studies we use sedation.

If the catheter is not in the antecubital vein, handinjection is preferred.

Scan Initiation TimeBolus tracking is used and the trigger is set at 120HU.This may not always work, because in small childrenthe amount of contast may be too small to trigger ordue to breathing the cursor may fall to the lungs.If bolus tracking does not trigger, start the scan at 15seconds.

Positioning the ROI

l Ascending aorta for aorta and superior vena caval Main PA for pulmonary arteriesl Left Atrium for pulmonary veins

Post-processingMultiplanar reconstructions (MPR), volume renderedtechniques (VRT) and maximum intensity (MIP) arevery helpful.




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References

1. MDCT Evaluation of Thoracic Aortic Anomalies in Pediatric Patients and Young Adults: Comparison of Axial,

Coronal MPR (left), external volume rendering (middle) andinternal volume rendering.

There is no role for shaded surface or mini-IP's.On the left an external and internal rendering whichprovides in contrast to MPR real 3D information.In volume rendering the posterior view is preferred to

get a good look at the arch and descending aorta.

Thick slab maximal intensity projection to study the

pulmonary vasculature.

If you want to study peripheral vessels you will needthick slab maximal intensity projections.For instance if you study arteriovenous malformationsor discrepancy in lung flow.

Thick slab coronal maximal intensity projection image in

patient with scimitar syndrome.

Notice that on the coronal MIP you can nicely see thedifference in vascularization of the lungs withhypovascularity on the right in a patient with scimitarsyndrome.

High grade coarctation of aorta not seen on axial images butclearly visualized on sagittal MPR.

3D reconstructions are helpful when there are shortfocal lesions like coarctation or when vessels courseobliquely (figure).Adding 3D reconstructions to axial images willincrease the sensitivity from 90% to 100% (Lee,Siegel AJR 182:777-784 )On the left a 17-day old boy with minimal cyanosis,mild heart failure and upper extremity hypertension.On axial images you will have trouble diagnosiscoarctation, because it is focal and in the same planeas the axial image.

If you want to read more about pediatric body CT,buy:Pediatric Body CT, 2nd edition. LippincottWilliams & Wilkins, Philadelphia. 2008 (3) byMarilyn Siegel.




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Multiplanar, and 3D Imagesby Edward Y. Lee, Marilyn J. Siegel, Charles F. Hildebolt, Fernando R. Gutierrez, Sanjeev Bhalla and Juliet H. Fallahof the Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway Blvd., St.Louis, MO 63110.

AJR 2004; 182:777-784

2. Diagnostic Imaging: ChestBy Jud Gurney, MD et alAMIRSYS Title, ISBN: 1416023348, ISBN-13: 9781416023340This book represents today's best single source of guidance on chest diagnostic imaging!

3. Great vessels. In: Pediatric Body CT, 2nd editionby Marilyn SiegelLippincott Williams & Wilkins, Philadelphia. 2008

4. Angiography and dynamic airway evaluation with MDCT in the diagnosis of double aortic arch associated withtracheomalacia.Chan MSM, Chu WCW, Cheung KL, Arifi AA, Lam WWMAJR 2005; 185:11248-1251


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