Pulmonary Arteriovenous Fistulae Clinical Presentation

Symptoms caused by pulmonary arteriovenous malformations (AVMs) are often insidious, as the arteriovenous malformations slowly enlarge.

Dyspnea, especially with exercise, may develop over many years. In severe cases, dyspnea in the upright position (platypnea) may be present. Visible cyanosis may be present if a significant degree of desaturation is present.

Hemoptysis and rarely massive hemoptysis may occur.

Less common complaints include chest pain, cough, migraine headaches, tinnitus, dizziness, dysarthria, syncope, vertigo, and diplopia. The cause of these symptoms is not entirely clear, but it may be related to hypoxemia, polycythemia, or paradoxical embolization through the pulmonary arteriovenous malformations.

Murmurs or bruits over the location of the pulmonary arteriovenous malformations are heard in patients with large pulmonary arteriovenous malformations. These murmurs are most audible during inspiration and are called machinery murmurs.

Digital clubbing and cyanosis may be observed.

The phenomenon of orthodeoxia (desaturation with upright position) is characteristic. Because pulmonary arteriovenous malformations are more frequently found in the lower lobes, with upright position, more blood is directed to the lower lobes because of the effects of gravity, exacerbating the degree of shunting. In addition, platypnea (dyspnea with upright position) may also be noted because of the increased degree of cyanosis.

Because most patients with pulmonary arteriovenous malformations also have HHT, the characteristic mucocutaneous telangiectasias are frequently observed in patients with pulmonary arteriovenous malformations. These lesions are papular, slightly rounded, and sharply demarcated from surrounding skin. They have a few dendritic projections that are ruby colored and partially blanche with pressure. The lesions are present on the face, mouth, chest, and upper extremities (see the image below).

Certainly, the finding of mucocutaneous telangiectasias should prompt a workup for HHT and include evaluation for pulmonary arteriovenous malformations.

Epidemiology

Great heterogeneity of symptoms is noted among different families and within single large families with HHT. Some families with HHT predominantly have the pulmonary arteriovenous malformations and cerebral arteriovenous malformations; whereas other affected families predominantly have GI mucosal telangiectasis, which lead to GI bleeding and iron-deficiency anemia.

Inheritance

HHT is an autosomal dominant disorder; however, 20% of cases involve no family history of telangiectasia or recurrent bleeding. Penetrance is age related and nearly complete by age 40 years. Although the arteriovenous malformations in HHT are inherited and should be present at birth, they commonly manifest clinically during adult life, after the vessels have been subjected to pressure for several decades.

Associated syndromes

Communication between pulmonary arteries and pulmonary veins has been reported in cases of trauma and in hepatic cirrhosis, schistosomiasis, mitral stenosis, actinomycosis, Fanconi syndrome, and metastatic thyroid carcinoma. Communications between bronchial arteries and pulmonary arteries that cause a left-to-right shunt develop in chronic inflammatory conditions such as bronchiectasis. Most individuals with pulmonary arteriovenous malformations have HHT. The diagnostic criteria for a definite diagnosis of HHT include at least 3 of the following:

• Recurrent and spontaneous epistaxis
• Multiple mucocutaneous telangiectases
• Visceral lesions (eg, GI arteriovenous malformations, pulmonary arteriovenous malformations)
• First-degree relative with HHT by these criteria

Associated noncardiac conditions

The most frequently reported associated noncardiac conditions are CNS complications, which occur in 30% of patients. Strokes occur in 18% of patients with CNS complications, transient ischemic attacks occur in 37%, brain abscesses occur in 9%, migraine headaches occur in 43%, and seizures occur in 8%. Paradoxic embolism across pulmonary arteriovenous malformations is the most likely mechanism for major noninfectious strokes. Embolism of infected material accounts for solitary or recurrent brain abscesses. These complications most commonly occur when the feeding arteries are larger than 3 mm in diameter. Hemoptysis and hemothorax are other potentially life-threatening complications. Hemoptysis occurs from ruptured pulmonary arteriovenous malformations or endobronchial telangiectasia.

Idiopathic congenital pulmonary arteriovenous malformations

Idiopathic congenital pulmonary arteriovenous malformations are likely to be single. They are less likely to become enlarged, and the are associated with fewer physical findings than other pulmonary arteriovenous malformations. Idiopathic pulmonary arteriovenous malformations are diagnosed by using the same criteria as for other pulmonary arteriovenous malformations. Idiopathic congenital pulmonary arteriovenous malformations are successfully treated with embolotherapy.

Acquired arteriovenous malformations in hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS), increased alveolar-arterial oxygen gradient, and intrapulmonary right-to-left shunting (defined as the triad of liver disease) may occur in as many as 47% of patients with end-stage liver disease. All types of chronic liver disease may give rise to this syndrome. Approximately 80% of affected patients have signs and symptoms of end-stage liver disease before symptoms from pulmonary arteriovenous malformations develop. These patients have dyspnea, platypnea, clubbing, cyanosis, hypoxia, and orthodeoxia. Pulmonary function results indicate normal lung volumes and expiratory flow rates with low diffusing capacity.

In contrasts to patients with HHT, patients with HPS rarely have discrete arteriovenous malformations on chest radiographs. The calculation of the shunt fraction with the use of 100% oxygen, contrast echocardiography, and radionuclide scanning are diagnostic tests for HPS.

Results of HPS management have been disappointing. Liver transplantation may result in the resolution of HPS, and HPS is not a contraindication to liver transplantation. An improvement in HPS-related pulmonary shunting after therapeutic transjugular intrahepatic portosystemic shunting has been described.

Acquired arteriovenous malformations after surgery for congenital cyanotic heart disease: Pulmonary arteriovenous malformations may develop after Glenn or modified Fontan procedures for congenital cyanotic heart disease. Pulmonary arteriovenous malformations are a known late complication of Glenn anastomosis (ie, superior vena cava [SVC] to right pulmonary artery [RPA]), which occur in as many as 25% of cases. The Fontan operation (ie, SVC to right atrium and proximal RPA; hepatic veins to left pulmonary artery) was designed as a surgical repair for congenital tricuspid atresia. Contrast echocardiography and radionuclide shunt studies have been used to diagnose pulmonary arteriovenous malformations, and embolotherapy has been used successfully to occlude the pulmonary arteriovenous malformations in these cases.