Pulmonary arteriovenous malformation is a congenital vascular anomaly characterized by the presence of direct communication between the branches of the pulmonary artery and the pulmonary veins and the discharge of non–oxygenated blood into the arterial bed. In the clinic of PAVM, signs of arterial hypoxemia prevail: cyanosis, shortness of breath, weakness, deformation of the distal phalanges of fingers and nails. The diagnosis is clarified with the help of radiography and CT of the lungs, angiopulmonography, perfusion scintigraphy, blood gas composition studies. With arteriovenous aneurysm of the lungs, symptomatic therapy, endovascular occlusion of the anastomosis or resection of the lung is possible.
Q25.7 Other congenital anomalies of the pulmonary artery
Pulmonary arteriovenous malformation (PAVM) is an embryonic disorder of the formation of lung vessels, in which there is a communication between arterial and venous vessels and right-left intrapulmonary bypass of blood. In pulmonology, PAVM is an infrequent finding; its prevalence does not exceed 2-3 cases per 100 thousand population. Despite the predominantly congenital nature of pulmonary arteriovenous malformation, only in 10% of cases clinical manifestations of pathology occur in childhood. In other patients, the manifestation of the disease occurs in the second, third and fourth decades of life. PAVM is diagnosed in men and women with approximately the same frequency. In the literature, lung AV is also described under the names arteriovenous fistula, cavernous angioma, hemangioma, telangiectasia, cavernous sinus, arteriovenous malformation of the lungs.
Pulmonary arteriovenous malformation causes
In 80% of cases, PAVM are congenital, primary vascular malformations. The reasons for their formation, as well as other lung malformations, are associated with various prenatal hazards: radiation, electromagnetic, chemical, biological effects on the fetus, toxicosis and diseases of the pregnant woman, etc. Primary PAVM can be isolated anomalies or serve as part of congenital syndromes, in particular, hereditary hemorrhagic telangiectasia, or Randu-Osler-Weber disease. The structure of this hereditary disease is the presence of multiple telangiectasias and angiomas on the skin and mucous membranes, arteriovenous anastomoses in the lungs, a tendency to bleeding of various localizations. A combination of pulmonary arteriovenous malformation with congenital heart defects is possible.
Secondary PAVM that form after birth due to other diseases are much less common: cirrhosis of the liver, infectious lung lesions (actinomycosis), mitral stenosis, metastatic carcinomas, etc. In macroscopic examination, an arteriovenous aneurysm is determined as a thin-walled cystic formation in the lung, sometimes with a lobular structure. Blood clots are usually found on the incision in the aneurysm cavity, and fibrolipid and calcareous deposits are found in the walls.
Pulmonary arteriovenous malformation can be single (60-70%) or multiple (30-40%). Three quarters of patients have unilateral lung damage, the rest are bilateral. In most cases (65-70%), the location of arteriovenous aneurysms is the lower lobes of the lungs, more often on the right. There are simple pulmonary arteriovenous malformation (when communicating one artery with one vein) and complex arteriovenous malformations (when communicating two or more feeding arteries with several draining veins).
Interstices between arteries and veins can form at the level of segmental, subsegmental pulmonary vessels, arterioles and precapillaries. If medium- and large-caliber vessels communicate with each other, then the pathology is classified as an arteriovenous fistula; anomalies of smaller vessels forming baggy extensions are usually attributed to arteriovenous aneurysms. In shape, PAVM can be rounded, oval, pear-shaped or cluster-shaped, consisting of several cavities of various sizes (from 1 to 5-10 cm).
Pulmonary arteriovenous malformation symptoms
The severity of symptoms in PAVM can vary widely: from complete absence of manifestations to severe forms of cardiopulmonary insufficiency. This depends mainly on the number and size of PAVM. Thus, single pulmonary arteriovenous malformation with a diameter of less than 2 cm are usually asymptomatic; more often the clinic develops with multiple vascular anomalies. The classic triad of symptoms of PAVM is dyspnea, cyanosis, thickening of the terminal phalanges of the fingers with deformed nails (“Hippocratic fingers”), but these signs occur only in 10% of patients. Quite often there are chest pains, cough, increased fatigue with physical exertion, hemoptysis. The consequence of hypoxemia are dizziness, syncopal states.
When PAVM is combined with Randu-Osler-Weber disease, nasal and gastrointestinal bleeding, hemorrhages from cutaneous telangiectasia, leading to posthemorrhagic anemia, are typical. Complications of PAVM can be septic, hemorrhagic, thromboembolic conditions. The most common are cerebrovascular lesions, including migraine headaches, transient ischemic attacks, and ischemic stroke. In the presence of inflammation in the pulmonary arteriovenous malformation, brain abscess and infectious endocarditis may occur. In case of rupture of the aneurysmal sac, profuse pulmonary bleeding develops into the bronchial lumen, and hemothorax develops into the pleural cavity.
At the initial appointment with a pulmonologist, complaints and the duration of the disease, its connection with concomitant pathology are clarified; a physical examination is carried out. Auscultative phenomena characteristic of arteriovenous aneurysm of the lungs include systodiastolic noise, increasing on inspiration, “cat purring”, “top” noise. Objectively, cyanosis of the skin and visible mucous membranes, deformation of the fingers in the form of “drumsticks” and nails by the type of “watch glasses” are determined. Laboratory analysis data (hemograms, blood gas composition studies) reveal polycythemia, a decrease in blood oxygen saturation.
On lung x-ray, arteriovenous aneurysms are detected as single or multiple rounded, clearly defined darkenings, more often in the projection of the lower lobe. The vascular nature of the pathology is confirmed during the functional tests of Valsalva and Muller: in this case, the fluctuation of intra-thoracic pressure entails an increase or decrease in blood flow to the aneurysm and a change in its size. More accurate information about the nature of the formation can be obtained using angiopulmonography and MSCT angiography with contrasting pulmonary vessels, perfusion scintigraphy of the lungs. X-ray contrast studies make it possible to visualize the feeding and draining vessels, pathological shunting of blood from the artery to the diverting vein. Differential diagnosis is carried out with lobar emphysema, tuberculoma, solitary air cysts of the lungs.
Pulmonary arteriovenous malformation treatment
Therapeutic tactics in relation to PAVM may be different. In the case of multiple small vascular malformations, it is necessary to limit conservative symptomatic therapy. For small single arteriovenous aneurysms, interventional surgery – transcatheter endovascular occlusion of the arteriovenous anastomosis is the method of choice. In other cases, depending on the level of lesion and the caliber of communicating vessels, resection interventions are indicated, the volume of which can vary from atypical resection and segmentectomy of the lung to lobectomy or pneumonectomy.
- Can aura migraine be elicited by isolated pulmonary arteriovenous fistula?-A case report. Onorato EM, Salvia J, Becchina M, Cipolla T, Anzola GP. Front Neurol. 2022 Dec 15;13:1079959. link
- Spontaneous hemothorax in pregnant patient with pulmonary arteriovenous malformation. Robinson TJ, Anamah B, Winter WB, Imani-Shikhabadi R. Radiol Case Rep. 2022 Dec 5;18(2):679-684. link
- The Role of Interventional Radiology in the Diagnosis and Treatment of Pulmonary Arteriovenous Malformations. Yap CW, Wee BBK, Yee SY, Tiong V, Chua YX, Teo L, Lohan R, Tan A, Singh P, Rajendran PC, Yang C, Yee YC, Anil G, Ong SJ. J Clin Med. 2022 Oct 25;11(21):6282. link
- Bronchoscopy-guided removal of intrabronchial coil migration after coil embolization of pulmonary arteriovenous malformation. Hu TX, Oh SS, McWilliams JP. Radiol Case Rep. 2022 Jul 21;17(9):3410-3414 link
- Bilateral Lung Transplantation for Congenital Pulmonary Arteriovenous Fistula with Intraoperative Venovenous ECMO Support: The First Case Report in China. Liang J, Chen Y, Zhou J, Zheng M, Liu F, Ye S, Chen J, Ji Y. Front Surg. 2022 May 31;9:861797. link