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Case of the Season:Pulmonary Arteriovenous MalformationJason Tsai, MD, and Edward Y. Lee, MD, MPH

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A13-year-old girl presented to her primary care providerwith progressively worsening fatigue and shortness of

reath over the past 2 years. The patient was previouslyealthy, without known significant underlying medical prob-

ems or recent acute illness. Vital signs were notable for anxygen saturation of 85% on room air. On physical exami-ation, lungs were found to be clear to auscultation, with novidence of respiratory distress. Laboratory findings were un-emarkable, including a normal white blood cell count.

Because of the patient’s low oxygen saturation, inpatientdmission was obtained. Initial chest radiographs revealed aobulated opacity in the left lower lung, concerning for aossible pulmonary mass (Fig. 1). Contrast-enhanced com-uted tomography angiography (CTA) of the chest was per-ormed to further characterize this abnormality.

On CTA, a smoothly marginated, homogeneously enhanc-ng 7.5- � 4-cm mass was identified in the left lower lobe,emonstrating contrast enhancement characteristics similaro adjacent vessels (Fig. 2). Anomalous feeding arteries fromhe left main pulmonary artery and draining veins into the leftnferior pulmonary vein were also visualized, confirming theiagnosis of pulmonary arteriovenous malformation (AVM)Fig. 2).

DiagnosisPulmonary AVMFollowing the diagnosis of pulmonary AVM, the patient un-derwent transcatheter embolization of her large left pulmo-nary AVM (Fig. 3). Two dominant feeding pulmonary arterialbranches were identified and selectively occluded using em-bolic coils and Amplatz vascular plugs, without immediatecomplication. At least 2 smaller pulmonary arterial branchesserving a different component of the pulmonary AVM were

Department of Radiology, Children’s Hospital Boston and Harvard MedicalSchool, Boston, MA.

Address reprint requests to Edward Y. Lee, MD, MPH, Division of ThoracicImaging, Department of Radiology, Children’s Hospital Boston andHarvard Medical School, 300 Longwood Avenue, Boston, MA 02115.

E-mail: Edward.Lee@childrens.harvard.edu.

4 0037-198X/12/$-see front matter © 2012 Elsevier Inc. All rights reserved.doi:10.1053/j.ro.2011.10.003

seen, but could not be accessed before the procedure wasended, to limit radiation dose and contrast load.

Following embolotherapy, the patient initially experi-enced relief of symptoms and significant improvement inoxygenation. However, within 2 months, oxygenation levelsbegan to decline, and follow-up imaging demonstrated rep-erfusion of the pulmonary AVM, which had substantiallyincreased in size. The patient returned to the interventionalsuite, where 2 large feeding vessels were found and emboli-zed with coils and Amplatz plugs.

After 1 year of follow-up, the patient remains active, butwith mildly decreased oxygen saturations during exercise.Repeat imaging has demonstrated reperfusion of the pulmo-nary AVM, with multiple feeding branches from left upperand lower lobar pulmonary arteries. The patient is currentlyscheduled for additional transcatheter embolization of thepulmonary AVM.

DiscussionPulmonary AVM, also known as arteriovenous fistula, is acondition in which there is an abnormal direct connectionbetween pulmonary artery and vein.1 Although the exact eti-logy for developing pulmonary AVM is currently unknown,t has been postulated that a developmental defect in theormation of normal pulmonary capillaries may be the causef this condition.1 While most pulmonary AVMs are congen-tal, most patients remain asymptomatic until the fourth de-ade of life. Only about 10% are diagnosed in infancy andhildhood, with increasing incidence through the fifth andixth decades of their lives.1 Acquired pulmonary AVM issually present in patients with long-term lung disease,rauma, history of infection (eg, tuberculosis, actinomycosis,nd schistosomiasis), or prior congenital cyanotic heart sur-eries (eg, Glenn and Fontan procedures).2

An estimated 60%-90% of all cases of pulmonary AVMare associated with hereditary hemorrhagic telangiectasia(HHT), also known as Rendu–Osler–Weber syndrome.3

Conversely, 15%-35% of patients with HHT have pulmonaryAVM.1 Therefore, family members with HHT should bescreened for pulmonary AVMs. HHT is an autosomal domi-

nant disorder, which results in abnormal blood vessel forma-

Pulmonary arteriovenous malformation 5

tion in the skin, mucous membranes, and often in solid or-gans including lungs, liver, and brain. This condition ischaracterized by a classic triad of epistaxis, telangiectasia,and positive family history.2-4

In providing direct communication between pulmonaryarteries and veins, pulmonary AVM can manifest clinicallythrough a variety of mechanisms. Right-to-left blood shuntedthrough the malformation bypasses capillaries and is not ox-ygenated, leading to hypoxemia. Patients with pulmonaryAVM, therefore, often present with dyspnea, which is themost common presenting pulmonary complaint, as seen inour patient. Absence of intervening capillaries also removestheir filtering effect, allowing direct passage of air or solidparticles into the systemic circulation. Resulting paradoxicalemboli may cause significant neurologic sequelae, includingstroke and intracranial abscess. Finally, rupture of abnormalvessels may lead to hemoptysis or hemothorax.3,5

On chest radiographs, pulmonary AVM usually appears asa well-marginated pulmonary lesion, as seen in our patient.6

Associated curvilinear opacities representing a feeding arteryand a draining vein coursing toward the hilum can be some-times seen. In a patient with suspected pulmonary AVM,contrast-enhanced multidetector computed tomography us-ing CTA protocol is the current diagnostic test of choice, witha sensitivity and specificity at least comparable with that ofmore invasive pulmonary angiography.5,6 Computed tomog-raphy (CT) can provide detailed anatomic information aboutpulmonary AVM, including lesion size, shape, and location,as well as the angioarchitecture of associated anomalousvessels—information critical to therapeutic planning.6 On

Figure 1 Frontal chest radiograph shows an oval-shaped mass-likeopacity (arrows) in the left lower lung zone.

CT, pulmonary AVM typically appears as a nodule or mass

demonstrating contrast enhancement, with associated en-

Figure 2 (A) Enhanced axial computed tomography image demon-strates a large vascular mass (AVM, arteriovenous malformation)located in the left lower lobe with an anomalous vein (arrow) drain-ing into the left inferior pulmonary vein. (B) Enhanced coronalmaximum intensity projection image shows a large vascular mass(AVM) with an anomalous feeding artery (arrow) from the left mainpulmonary artery. (C) 3D volume-rendered image demonstrates apulmonary AVM with an anomalous feeding artery (arrow) and ananomalous draining vein (curved arrow). (Color version of figure is

available online).

it

blood supply to the pulmonary AVM.

6 J. Tsai and E.Y. Lee

larged feeding artery and draining vein.6 Pulmonary AVMcan be categorized as simple, with single feeding artery andsingle draining vein, or complex, with 2 or more feeding anddraining vessels. Pulmonary AVMs have a predilection for thelower lobes and can be multiple in more than a third ofcases.1,7 A feeding artery with a diameter of 3 mm or greaters considered clinically significant in terms of shunting, andhus a candidate for treatment.1,6 Generally, pulmonary

AVMs can be distinguished from other vascular pulmonarylesions because of the presence of both feeding artery fromthe pulmonary artery and draining vein into the pulmonaryvein.

Transcatheter embolization has been demonstrated to be asafe and effective means of treatment for pulmonary AVM inboth adults and children. It has supplanted surgery as themainstay in the management of these lesions, with long-termsuccess rates of more than 80%.7,8 Steel or platinum coils arenow favored in the embolization of pulmonary AVMs, oftenin combination with vascular plugs. As in adults, however,up to 15% of PAVM will reperfuse following embolization,necessitating retreatment as seen in our patient. This under-scores the importance of long-term follow-up for patientswith treated pulmonary AVM.9

In summary, pulmonary AVMs are uncommon entities,particularly in children, that nevertheless can lead to poten-tially serious hemorrhagic and neurologic complications ifleft untreated, including hemoptysis, hemothorax, stroke,and cerebral abscess. Most cases are congenital and associ-ated with HHT. Contrast-enhanced MDCT using CTA pro-tocol is the current diagnostic modality of choice in the eval-uation of pulmonary AVM. Transcatheter embolization hasproven to be an effective first-line treatment. In a minority ofpatients, reperfusion of PAVM necessitates retreatment, un-derscoring the need for long-term follow-up.

References1. Gossage JR, Kanj G: Pulmonary arteriovenous malformations: A state of

the art review. Am J Respir Crit Care Med 158:643-661, 19982. Iqbal M, Rossoff LJ, Steinberg HN, et al: Pulmonary arteriovenous mal-

formations: A clinical review. Postgrad Med J 76:390-394, 20003. Shovlin CL, Letarte M: Hereditary haemorrhagic telangiectasia and pul-

monary arteriovenous malformations: Issues in clinical management andreview of pathogenic mechanisms. Thorax 54:714-729, 1999

4. Grand’Maison A: Hereditary hemorrhagic telangiectasia. CMAJ 180:833-835, 2009

5. Liechty KW, Flake AW: Pulmonary vascular malformations. Semin Pe-diatr Surg 17:9-16, 2008

6. Carette MF, Nedelcu C, Tassart M, et al: Imaging of hereditary hemor-rhagic telangiectasia. Cardiovasc Intervent Radiol 32:745-757, 2009

7. Lee EY, Boiselle PM: Tracheobronchomalacia in infants and children:Multidetector CT evaluation. Radiology 252:7-22, 2009

8. Mager JJ, Overtoom TT, Blauw H, et al: Embolotherapy of pulmonaryarteriovenous malformations: Long-term results in 112 patients. J VascInterv Radiol 15:451-456, 2004

9. Faughnan ME, Thabet A, Mei-Zahav M, et al: Pulmonary arteriovenousmalformations in children: Outcomes of transcatheter embolotherapy.

Figure 3 (A) Frontal view of the conventional angiography imageobtained with contrast injection into the left main pulmonary arteryshows a large vascular pulmonary AVM with 2 large feeding arteries(arrows). (B) Frontal view of the conventional angiography imageobtained after the embolization of the feeding arteries associatedwith a large pulmonary AVM demonstrates a markedly decreased

J Pediatr 145:826-831, 2004