AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Background

First described in 1897, pulmonary arteriovenous malformation (PAVM) is an abnormal communication between the pulmonary artery and the pulmonary vein. PAVMs are usually congenital in origin; however, they may be acquired in a variety of conditions, such as hepatic cirrhosis, schistosomiasis, mitral stenosis, trauma, actinomycosis, and metastatic thyroid carcinoma.

After the initial description of telangiectasia and epistaxis by Henry Jules Rendu, in 1896, Sir William Osler reported a family known to have hereditary hemorrhagic telangiectasia (HHT). In 1907, Frederick Weber described other manifestations of this disorder; since then, HHT has come to be known as Rendu-Osler-Weber syndrome (or, alternately, as Osler-Weber-Rendu syndrome). Approximately 70% of PAVMs are associated with HHT, and about 15-30% of individuals with HHT have a PAVM.¹ (Also, see the eMedicine article Osler-Weber-Rendu Syndrome.)

For excellent patient education resources, visit eMedicine's Cancer and Tumors Center and Liver, Gallbladder, and Pancreas Center. Also, see eMedicine's patient education articles Lung Cancer and Cirrhosis.

Pathophysiology

In HHT, telangiectases and arteriovenous malformations (AVMs) are the 2 primary vascular abnormalities. Telangiectasia is a localized, convoluted enlargement of the postcapillary venule, and it involves smooth muscle proliferation and perivascular lymphocytic infiltration. An AVM is a direct connection between the pulmonary artery and the pulmonary vein, and it may be associated with dilatation and localized aneurysmal enlargement of the feeding vessel.

Approximately 50-70% of PAVMs are located in the lower lobes. About 70% of patients have unilateral disease, 36% have multiple lesions, and 50% may have bilateral disease. The size of the PAVMs may vary from microscopic to the typical size of 1-5 cm.

Pathogenesis

Although their pathogenesis is not well delineated, PAVMs are considered to result from incomplete resorption of the vascular septa. These vascular septa separate the arterial plexus and the venous plexus, which normally anastomose during fetal development. Progressive dilatation of the smaller plexus leads to the formation of tortuous loops and multiloculated sacs. With rupture of intervening vascular walls, a single large, saccular PAVM develops.

Genetics of HHT

Some of the genetics of HHT have been elucidated. These genetic abnormalities may also be present in patients with PAVM who do not have HHT. Two linkage groups for HHT have been discovered: HHT1 has been linked to band 9q33, and HHT2 has been linked to band 12q13. Endoglin is identified as the gene product for HHT1 on band 9q33. Approximately 13 mutations of the endoglin gene have been reported. Endoglin and activin receptorlike kinase-1 (ALK-1) protein bind transforming growth factor beta (TGF beta), which is implicated in angiogenesis. PAVM likely develops as a result of the interplay of various factors among diverse cells and the matrix as a result of vascular insults from a variety of causes.

Frequency

United States

Three cases of PAVM were detected in 15,000 autopsies performed at Johns Hopkins Hospital in 1953. At the Mayo Clinic, 63 cases were detected during the 20 years ending in 1972.² Over the subsequent 9 years, ending in 1981, 38 additional cases were encountered.² Overall, the frequency of PAVM may be variable, but it generally appears to be 1 case per 39,216 persons.

International

Regional variations in frequency are known to occur. A frequency as high as 1 case per 2351 persons has been reported in some regions of France.

Mortality/Morbidity

• Short-term follow-up studies have revealed mortality rates of 0-15%.
• Morbidity may be significant and includes stroke, brain abscess, massive hemoptysis, infective endocarditis, and congestive heart failure.

Sex

PAVM occurs twice as often in women as in men, but a male predominance exists in newborns.

Age

Approximately 10% of PAVM cases are identified in infancy or childhood; however, the incidence gradually increases through the fifth and sixth decades of life.

Anatomy

The PAVMs consist of vascular channels that are thin walled and lined with endothelium. They have minimal connective-tissue stroma and drain into the left atrium. The malformation may appear as a large single sac, a plexiform mass of dilated vascular channels, or a dilated, tortuous, direct communication between the pulmonary artery and the pulmonary vein.

PAVMs can be classified as simple or complex types, based on their architecture. Simple PAVMs have a single feeding segmental artery leading to single draining pulmonary vein. Approximately 79% of PAVMs are of the simple type and occur in lower lobes; these are associated with nonseptate aneurysms. Approximately 21% of PAVMs are complex; these have 2 or more feeding arteries or draining veins. They often occur in the distributions of the lingula and the right middle lobe.

Clinical Details

General clinical presentation

The clinical presentation of PAVMs may vary from no symptoms to severe illness. Symptoms generally develop between the fourth and fifth decades of life. Symptoms occur more commonly in patients who have PAVM and HHT than in those who have PAVM without HHT.

The most common initial complaint is epistaxis. Dyspnea is the second most common complaint. Patients may also describe platypnea. Hemoptysis is the third most common symptom, and occasionally, massive hemoptysis may occur.

Patients may also develop gastrointestinal hemorrhage (15-30%). The other less-common clinical features are chest pain, coughing, dizziness, syncope, polycythemia, and cerebral vascular complications.

The most common physical finding in patients with PAVM is superficial telangiectases. These lesions generally appear on the face, mouth, chest, and upper extremities. Patients may also have digital clubbing and cyanosis. On auscultation of the lungs, a murmur may be heard over the PAVM; this is most audible during inspiration.

The patients may eventually develop signs and symptoms of congestive heart failure and/or respiratory failure.

Other clinical presentations

Idiopathic congenital PAVMs are congenital PAVMs that are not associated with HHT. These PAVMs are likely single and are associated with fewer physical findings than other types. These PAVMs have a natural history similar to that of other PAVMs.

PAVMs may present with primarily neurologic manifestations when pulmonary symptoms are absent or unrecognized. Brain abscess, embolic stroke, and hemorrhage from concomitant brain AVM are well-recognized complications.³ The pathogenesis of neurologic complications is not entirely known, but embolization of thrombus or the infected material appears to be the most plausible explanation.

Acquired AVMs may occur in patients with hepatopulmonary syndrome. Approximately 47% of patients with end-stage liver disease acquire abnormal arterial venous communications. These patients have dyspnea, platypnea, clubbing, cyanosis, hypoxemia, and orthodeoxia.

Acquired AVMs may also appear after surgery for congenital cyanotic heart disease. PAVMs may develop following Glenn or modified Fontan procedures for the treatment of congenital cyanotic heart disease. PAVMs are late complications of both of these procedures. The clinical features of these PAVMs are similar to those of other PAVMS, and therefore, the surgery-related PAVMs are similarly diagnosed.

Preferred Examination

Diagnostic approach in a patient with a suspected PAVM

A PAVM may be suspected in the following clinical situations:

• An incidental finding of a solitary pulmonary nodule on chest radiographs
• The presence of mucocutaneous telangiectases
• A situation in which the patient presents with clinical findings of dyspnea, hemoptysis, hypoxemia, polycythemia, clubbing, cyanosis, cerebral embolism, or brain abscess.

Whenever a PAVM is suspected, the presence of a right-to-left shunt should be confirmed by the performance of a 100% oxygen study, contrast-enhanced echocardiography, or radionuclide perfusion lung scanning. A definitive diagnosis is established by means of direct imaging of the PAVM with a contrast-enhanced study, such as a computed tomography (CT) scan or a pulmonary angiogram.

Imaging examination

Chest radiography reveals some abnormality in most patients. However, further evaluation is needed, with a test to confirm the presence of a right-to-left intrapulmonary shunt and with an imaging study to confirm the presence of PAVM.

Contrast-enhanced echocardiography is extremely sensitive in detecting clinically important PAVMs. If contrast-enhanced echocardiography is not available, radionuclide perfusion lung scanning may be used.

Contrast-enhanced CT scanning remains the criterion standard in the diagnosis of PAVM. Although pulmonary angiography is less sensitive than contrast-enhanced CT scanning, it is performed to accurately define the anatomy, specifically before therapeutic embolization is performed. Although pulmonary angiography may also be a criterion standard for confirmation of a PAVM, angiography is required only when further intervention is planned. Otherwise, in most situations, contrast-enhanced CT scanning is sufficient to confirm the diagnosis.

Although magnetic resonance imaging (MRI) is reportedly useful in the diagnosis of PAVM, it may be less useful than contrast-enhanced CT scanning. Therefore, if the plain chest radiographs suggest a PAVM, contrast-enhanced CT scan remains the preferred examination for confirming its presence.

Limitations of Techniques

Chest radiographs may suggest a PAVM, but these images are not helpful in distinguishing between the various causes of a lung nodule. Contrast-enhanced echocardiography may be useful for distinguishing between intracardiac and intrapulmonary shunts, although this identification may be difficult at times.

Contrast-enhanced CT scans may not depict microscopic PAVMs, but the diagnostic yield with spiral CT scanning has been improving. Pulmonary angiography is less sensitive in identifying small or microscopic PAVMs, and MRI has significant limitations in screening for small lesions and in differentiating PAVM from lesions of other causes.

DIFFERENTIALS

Section 3 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

RADIOGRAPH

Section 4 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Chest radiography is recommended for the initial evaluation of patients with HHT. PAVM may well be an incidental finding on a chest radiograph. A common radiographic finding is a round or oval mass of uniform opacity. The opacity may have sharply defined borders with occasional lobulation. The mass is usually 1-5 cm, and linear shadows are adjacent to the opacity; these are the feeding vessels. PAVMs are commonly present in the lower lobes, and approximately 50% of patients have 2-8 lesions.

Degree of Confidence

When the classic radiographic features are present on the chest radiograph in a patient with suspected PAVM, the diagnosis is certain. However, chest CT scanning is invariably required to confirm the finding.

False Positives/Negatives

Patients with microvascular telangiectases may have normal chest radiographic results. Of the 27 patients reported on in one series, the plain chest radiographic findings were strongly suggestive of PAVM in 6 patients, somewhat suggestive in 5 patients, and not suggestive in 6 patients. CT scanning may be more accurate than plain chest radiography in diagnosing PAVM. In a patient who has clinical features suggestive of PAVM but has a normal chest radiograph, further evaluation using other imaging modalities should be undertaken.

CT SCAN

Section 5 of 12  

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• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Contrast-enhanced CT scanning is the preferred imaging modality for confirming the diagnosis of PAVM. One study reported better sensitivity for PAVMs with ultrafast, contrast-enhanced CT scanning than with pulmonary angiography. CT scans depicted 98% of PAVMs in 20 patients, whereas angiography depicted only 60% of PAVMs.

Three-dimensional (3D), spiral CT scanning produces images of vascular structures that are continuously reconstructed. In one study, spiral CT scanning proved to be a better investigative tool than unilateral pulmonary angiography. The accuracy of 3D spiral CT scanning is reported to be more than 95%, and it may also be useful in identifying smaller PAVMs.⁴

Multidetector-row CT scanning

The development of multidetector-row CT (MDCT) scanning has resulted in a revolution in imaging capabilities. When compared with single–detector-row CT (SDCT) scanning, CT angiography with MDCT scanning provides superior imaging capabilities. The advantages include an increased per-second scanning area, the ability to retrospectively select the scanning width, the ability to routinely provide 1-mm collimation, and the possibility of higher resolution with no blooming of section thickness.^{5, 6, 7}

MDCT scanning also has several practical advantages in the evaluation of PAVM. These include volume imaging, with 3D displays of the volume data, and retrospective reconstruction of the CT scanning data in any plane with high resolution.⁶

Maximum-intensity projection (MIP) and surface rendering were the 3D techniques that were primarily applied to CT angiographic applications in the past. However, volume rendering is becoming the preferred 3D rendering technique for CT angiography.

Surface rendering

Surface rendering, the earliest method for 3D display, is commonly available and utilizes each voxel in the data set. The voxel intensity is compared with a threshold value, thereby defining the surface of the object, and the remaining data are discarded. Surface contours are typically modeled with surface shading; therefore, the resulting image is simplified and may provide a misleading representation of the structure. Conversion of data from a volume to a surface sacrifices a large portion of the data and limits the usefulness of surface-rendered medical images.

Maximum-intensity projection

MIP has been extensively utilized in creating angiographic images from CT scanning and MRI data. Each voxel is evaluated along a line through the image, and the value of the corresponding display pixel is selected based on the value the maximum voxel. The resulting images are typically not displayed with surface shading and increase the background mean of the image, thereby enhancing the structures. The problem with MIP is that volume averaging along with the algorithm may lead to artifacts. Despite its artifacts and deficiencies, MIP has been extensively evaluated and usually provides accuracy superior to that of surface rendering for CT angiography.

Volume rendering

This technique renders the entire volume of data rather than just the surfaces, with the total contributions of each voxel being utilized; therefore, more information is displayed than would be provided in a surface model. Volume technique is the most advanced form of 3D rendering currently available for creating accurate, clinically useful medical images and has revolutionized the field of vascular imaging.

Degree of Confidence

Contrast-enhanced CT scanning or spiral CT scanning is the standard of care for the diagnosis of PAVMs.

False Positives/Negatives

It may be difficult to differentiate a PAVM from a vascular tumor on a CT scan. In this situation, a false-positive diagnosis of PAVM is possible. Because prolonged breath holding is required, a large PAVM may be difficult to visualize on 3D spiral CT scans. Furthermore, CT scans may not depict microscopic or small PAVMs.

MRI

Section 6 of 12  

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• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Conventional MRI may be useful in detecting PAVMs. However, compared with other techniques, it has reduced sensitivity and specificity. Because rapidly flowing blood results in an absent or minimal MRI signal, a PAVM may be indistinguishable from normal vascular structures or an air-filled lung.

Various techniques have been used to improve the sensitivity of MRI. These include a rotating, gated MRI technique and gradient recalled-echo MRI. Some investigators have suggested that phase-contrast cine sequences are most accurate in detecting PAVM. Magnetic resonance angiography (MRA) has been used to define the vascular anatomy of a PAVM.

Degree of Confidence

Although a combination of MRI techniques may be useful in differentiating PAVMs from other lesions, more studies are required before the routine use of MRI can be recommended.

False Positives/Negatives

In research investigating the role of MRI in the diagnosis of PAVM and examining the modality's false-positive rates, a relatively small number of patients were studied. The sensitivity and specificity of magnetic resonance images are lower than those of CT scans. Furthermore, MRI techniques often yield conflicting results.

ULTRASOUND

Section 7 of 12  

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• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Contrast-enhanced echocardiography is used to confirm a right-to-left intrapulmonary shunt. Cardiac imaging with 2-dimensional echocardiography is performed while 5-10 mL of agitated sodium chloride solution is injected into a peripheral vein. In a healthy person, microbubbles are rapidly visualized in the right atrium before they gradually dissipate. When an intracardiac shunt is present, the contrast material is visualized in the left heart chambers within 1 cardiac cycle after it appears in the right atrium. The visualization of contrast material in the left atrium after a delay of 3-8 cardiac cycles confirms the presence of an intrapulmonary shunt (ie, PAVM).

Degree of Confidence

Contrast-enhanced echocardiography has high sensitivity in detecting right-to-left intrapulmonary shunts, such as PAVMs. This finding should be confirmed by using other tests. The finding of an intrapulmonary shunt during contrast-enhanced echocardiography still warrants further anatomic evaluation with contrast-enhanced CT or pulmonary angiography.

Contrast-enhanced echocardiography is generally not used as a first-line screening test because of its cost, limited availability, and possible overdetection of clinically insignificant PAVMs.

False Positives/Negatives

The sensitivity of contrast-enhanced echocardiography approaches 100%; therefore, false-negative test results are unlikely. No specific data address false-positive results; however, contrast-enhanced echocardiography may depict microscopic or clinically insignificant PAVMs.

NUCLEAR MEDICINE

Section 8 of 12  

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• Radiograph
• CT Scan
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• Ultrasound
• Nuclear Medicine
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• Intervention
• Multimedia
• References

Findings

Radionuclide perfusion lung scanning also is used in the diagnosis of PAVM, and the findings usually confirm a right-to-left shunt. This test is particularly useful if contrast-enhanced echocardiography or the 100% oxygen method is not available. The test involves the peripheral, intravenous injection of macroaggregated albumin labeled with technetium-99m (^99mTc). In healthy persons, these particles are filtered by pulmonary capillaries. However, in the presence of true right-to-left shunts, radiolabeled particles pass through the lungs and are trapped in the brain and kidneys. The shunt fraction may be calculated by quantifying the renal uptake as a percentage of the total dose given or lung uptake.

Degree of Confidence

Radionuclide scanning is accurate in detecting a right-to-left shunt, and it may have some advantages over the 100% oxygen method.

However, although radionuclide scanning is comparable to the 100% oxygen method in detecting PAVMs, its expense and limited availability prohibit its widespread use. Nonetheless, although the radionuclide method of shunt calculation is not routinely available at most hospitals, it has the following advantages over the 100% oxygen method:

• Radionuclide scanning does not require arterial blood gas sampling.
• The 100% oxygen method may cause overestimation of the intrapulmonary shunt.
• The radionuclide method is more suitable for shunt measurement during exercise.

False Positives/Negatives

Radionuclide perfusion scanning depicts only right-to-left shunts and is not useful in determining a shunt's intracardiac or intrapulmonary location.

ANGIOGRAPHY

Section 9 of 12  

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• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
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• Intervention
• Multimedia
• References

Findings

Contrast-enhanced pulmonary angiography should be used in the treatment of PAVM using embolization or prior to surgical treatment. This test is usually necessary to study the detailed anatomy of PAVM, particularly if the resection or obliterative therapy is planned. Furthermore, angiography may depict other unsuspected PAVMs, as well as unsuspected intrathoracic or extrathoracic vascular communications.

Digital subtraction angiography has replaced conventional angiography in the diagnostic imaging of PAVM. To the authors' knowledge, however, no systematic comparison of the 2 techniques has been reported in the literature. Because nonselective pulmonary angiograms may have difficulty depicting the anatomy of a PAVM, superselective pulmonary angiography is recommended.

Degree of Confidence

Pulmonary angiography has been the criterion standard for defining the anatomy of PAVMs. However, spiral CT scanning is now considered more appropriate for diagnosis.

False Positives/Negatives

Pulmonary angiography has high specificity but a sensitivity lower than that of contrast-enhanced ultrafast CT scanning or 3D spiral CT scanning.

INTERVENTION

Section 10 of 12  

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• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Shunt fraction measurement

The shunt fraction is most accurately assessed by using the 100% oxygen method. This method involves the measurement of PaO₂ and SaO₂ after the patient breathes 100% oxygen for 15-20 minutes. The fraction of cardiac output that is shunted as a result of right-to-left circulation is elevated in patients with PAVM (normal, <5%). In determining the presence of a shunt fraction of more than 5%, the 100% oxygen method has a sensitivity of 87.5% and a specificity of 71.4%.

Right heart catheterization

Most patients with PAVM have normal or low pulmonary arterial pressure. Despite severe oxygen desaturation, the mean pulmonary arterial pressure is low in most patients. The cardiac output is generally normal to moderately elevated. Several patients have developed new pulmonary hypertension or increased baseline pulmonary hypertension after the embolization or resection of a large PAVM.

Therapeutic embolization

The procedure of choice for treating a PAVM is therapeutic embolization rather than lung resection. Lung surgery is performed only when the PAVM is larger than 1 cm or when the risk of systemic embolization is significant.

Embolization therapy, or embolotherapy, is a form of treatment based on occluding the feeding arteries to a PAVM.

The first successful case of embolotherapy for the treatment of PAVM was reported in 1977 and involved the use of handmade steel coils. Since then, embolization with coils and/or detachable balloons has been reported in numerous series of more than 250 patients. Other embolic materials include polyvinyl alcohol, cotton wool coils, and stainless steel coils.

Indications

The indications for embolotherapy include the following:

• Progressive enlargement of the lesions
• Paradoxical embolization
• Symptoms
• Hypoxemia
• The presence of feeding vessels of 3 mm or larger

Technique

Coil embolotherapy involves localization of the PAVM by means of angiography, followed by selective catheterization of the feeding artery. A steel coil is advanced through the catheter and is placed distal to any branch of the vessel. Sometimes, more than 1 coil is required to completely occlude the vessel. Multiple PAVMs may be embolized in a single session.

The second embolotherapy technique uses detachable balloons. After the PAVM is localized, a balloon catheter is exchanged over a guide wire and positioned at the neck of the PAVM.

Results

Results of follow-up CT scanning at 1 or more years after embolotherapy indicate that 96% of PAVMs are undetectable or reduced in size.

One series followed up 45 patients who underwent embolotherapy of large (>8 mm) PAVMs.⁸ Approximately 98% of the PAVMs were occluded on the initial attempt, 84% of patients remained successfully treated, and 16% of patients had persistent PAVMs. The persistence of PAVMs was caused by recanalization of initially successful occlusion in 4 patients and by the interval growth of new feeding vessels in 3 patients. All 8 of the persistent PAVMs were successfully occluded during a second procedure, although 1 PAVM required a third procedure for permanent occlusion.

A summary of 10 published series of therapeutic embolizations for PAVM documented an average success rate of 98.7%. Balloon embolotherapy is generally used in a PAVM that has a feeding vessel larger than 7-10 mm.

Embolotherapy appears to be the treatment of choice because it avoids major surgery, general anesthesia, and the loss of the pulmonary parenchyma. Embolotherapy is a clear choice in patients with multiple or bilateral PAVMs or in patients who are poor candidates for surgery.

Postcatheterization care and precautions

Postcatheterization precautions include hemorrhage, vascular disruption after balloon dilation, chest pain caused by minor lung infarctions, nausea and vomiting, and arterial or venous obstruction caused by thrombosis or vasospasm.

Complications

Possible complications that have been reported are blood vessel rupture, tachyarrhythmias, bradyarrhythmias, and vascular occlusion. Pleuritic chest pain is the most common complication and is observed in 12% of patients. This pain usually responds well to analgesics. Radiographic evidence of pulmonary infarction is observed in 3% of patients.

An air embolism may occur during embolotherapy in 4.8% of patients. In these patients, transient symptoms, such as angina, perioral paresthesias, and bradycardia, may develop. Migration of the embolotherapeutic device distal to the PAVM has been reported in 1.2% of embolization attempts.

Long-term follow-up evaluation has revealed potentially serious complications in 2% of patients treated with embolotherapy. Symptomatic recanalization was observed with 0.5% of procedures.

New or increased pulmonary hypertension after embolization has been reported in several patients. The incidence of complication appears to be higher when feeding vessels larger than 8 mm are occluded.

Medical/Legal Pitfalls

• Because a PAVM may occur as a solitary pulmonary nodule on chest radiographs, a percutaneous needle biopsy may lead to catastrophic pulmonary hemorrhage. Therefore, PAVM should be considered in the differential diagnosis of a pulmonary nodule and excluded before a needle biopsy is performed.
• A chest radiograph should be obtained to rule out PAVM in patients presenting with a brain abscess.
• The family members of patients with HHT or PAVM should be screened with the methods described below in Special Concerns.
• Consider intrapulmonary shunts secondary to PAVM in the differential diagnosis of PAVM.

Special Concerns

• Screening of family members with PAVM or HHT
• • Family members of patients with HHT should be routinely screened for possible PAVM. The incidence of PAVM is approximately 15-20% in unselected patients with other clinical features of HHT. Whenever PAVM is diagnosed, screening of the patient's family members is particularly important. The incidence of PAVM is approximately 35% among relatives of persons with HHT and PAVM.
  • The evaluation of family members should be initiated with history taking, a focused physical examination, chest radiography, and a 100% oxygen shunt study.
  • Individuals with an increased shunt fraction on a 100% shunt study may be referred for contrast-enhanced CT scanning or pulmonary angiography. When patients with abnormal radiographic chest findings have a shunt fraction in the reference range, they should be referred for contrast-enhanced echocardiography or radionuclide perfusion scanning. If the subsequent exam results are abnormal, contrast-enhanced CT scanning or pulmonary angiography must be performed to confirm the diagnosis.
  • Routine screening of family members with CT scanning or contrast-enhanced echocardiography is expensive, and pulse oximetry is insensitive as a screening tool.
  • In cases of HHT, routine genetic screening of family members is likely to play an increasingly important role in the future. Once the genetic defect has been identified in a given family with HHT, genetic screening has 100% sensitivity and specificity for clinical HHT in individual family members. Therefore, in families with a known genetic mutation, genetic screening of all family members is recommended.
• Screening of pregnant patients
• • In pregnant women with HHT and PAVM, the risk of complications is significant. In one series, maternal complications occurred in almost 50% of pregnancies in patients with PAVM.
  • In pregnant women with PAVM, worsening of the right-to-left shunt, fatal pulmonary hemorrhage, and stroke may occur. Progression of the vascular malformations in the cerebral, pulmonary, and hepatic circulation during pregnancy also has been documented.
  • Because of the above factors, all women with HHT or a family history of HHT who are considering pregnancy should be screened for PAVMs.

MULTIMEDIA

Section 11 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Media file 1:  Gross anatomy of a large pulmonary arteriovenous malformation.
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Media file 2:  Pulmonary arteriovenous malformations in the left lower lobe were treated with coil embolization.
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Media file 3:  Close-up view of Image 2. Lateral chest radiograph shows a pulmonary arteriovenous malformation in the left lower lobe that was occluded with coil embolization.
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Media type:  X-RAY

Media file 4:  A small pulmonary arteriovenous malformation is depicted in the left lower lobe.
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Media type:  CT

Media file 5:  A 60-year-old patient presented with right cerebral infarction. The chest radiograph demonstrates a left–lower-lobe nodule, which was later identified as a pulmonary arteriovenous malformation.
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Media type:  CT

Media file 6:  Pulmonary angiogram of the same patient as in Image 5. The findings confirm a large pulmonary arteriovenous malformation with feeding vessels.
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Media file 7:  Three-dimensional computed tomography angiographic reconstruction of a pulmonary arteriovenous malformation in the same patient as in Images 5-6. The reconstruction utilized the volume rendering technique to enhance the image quality
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Media type:  CT

Media file 8:  Chest radiograph shows bilateral pulmonary arteriovenous malformations in a patient who presented with dyspnea and pulmonary hemorrhage.
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Media file 9:  Pulmonary arteriovenous malformation in the left upper lobe of the patient in Image 8.
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Media type:  CT

Media file 10:  Another pulmonary arteriovenous malformation in the left upper lobe of the same patient as in Images 8-9. This PAVM has already been embolized with a coil.
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Media type:  CT

Media file 11:  Pulmonary arteriovenous malformation in the right lower lobe of the same patient as in Images 8-10. This PAVM was previously embolized.
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Media type:  CT

Media file 12:  Chest radiograph demonstrating a peripheral opacity with feeding vessels radiating to the hilum. These features strongly suggest the presence of a pulmonary arteriovenous malformation.
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Media type:  Radiograph

REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

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5. Prokop M. General principles of MDCT. Eur J Radiol. Mar 2003;45 Suppl 1:S4-S10. [Medline].
6. Rubin GD. 3-D imaging with MDCT. Eur J Radiol. Mar 2003;45 Suppl 1:S37-41. [Medline].
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Article Last Updated: Oct 22, 2007