• pulmonary arteriovenous malformation (PAVM) comprises abnormal connections between pulmonary arteries and veins
    • synonyms:  pulmonary AVM, pulmonary arteriovenous fistula, pulmonary arteriovenous aneurysm
  • PAVMs are rare in the general population
    • it is estimated that 70-80% of PVAMs are related to HHT (hereditary hemorrhagic telangiectasia – Osler-Weber-Rendu), mainly HHT1 (10 times more than HHT2) → more about HHT see here
    • ≥ 15% of patients do not fulfill the criteria for a diagnosis of HHT and have no other systemic disease
  • neurological complications occur in ~ 50% of patients
    • paradoxical embolism can cause  TIA/stroke, ICH, or a cerebral abscess
    • concurrent cerebral AVM (CAVM) can cause ICH or epilepsy


  • direct arterio-venous shunts without embedded capillaries
  • PAVM, together with PFO, patent ductus arteriosus, and other congenital heart defects, is categorized as a condition at risk of paradoxical embolism
    • contrary to PFO, where the shunt is frequently seen only post-Valsalva maneuver, the shunt in PAVM is continuous
    • concurrent occurrence of PAVM and PFO is possible (consider the possibility of PAVM before PFO closure)

      • disproportionately massive and early shunt on the TCCD bubble test in the case of a small/moderate PFO on TEE should raise suspicion of another shunt
  • additional pathogenetic mechanisms besides paradoxical embolism include:
  • PAVMs may be located in any lung segment, with a predilection for the lower lobes
  • caused by any right-to-left shunt (RLS)
  • embolus type:
    • thrombus
    • fat
    • air
    • amniotic fluid
    • tumor tissue


  • according to the feeding artery
    • simple (2/3) – single feeding artery with a single draining pulmonary vein
    • complex (1/3) – multiple feeding arteries or draining veins
    • diffuse type (~5%) – dozens to hundreds of malformations
  • by other symptoms
    • isolated PAVM
    • PAVM in HHT (together with telangiectasias)

Clinical presentation

  • generally slow progression, with potential acceleration during pregnancy and adolescence
  • the clinical course differs between isolated PAVM and PAVM associated with HHT
  • symptoms most commonly occur between the 3rd and 6th decades of life
  • an asymptomatic course is observed in up to 50% of patients (mostly in PAVM < 2cm)
  • mortality and morbidity are mostly associated with stroke and brain abscess, less commonly with hypoxemic respiratory failure, hemoptysis, or hemothorax

Systemic and pulmonary symptoms

  • epistaxis (almost 100% incidence in HHT)
  • hemoptysis, dyspnea, chest pain
  • gastrointestinal (GIT) bleeding
  • cutaneous and mucosal telenagiectasias (in HHT) Rendu-Osler-Weber (Hereditary Hemorrhagic Telangiectasia)
  • myocardial infarction
  • peripheral infarcts (splenic, renal, mesenteric)

Neurological complications

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1. epistaxis, recurrent

2. telangiectasia

  • lips
  • oral cavity
  • fingers
  • nose

3. visceral lesions

  • GIT telenagiectasias
  • PAVM
  • hepatal AVM
  • cerebral AVM (CAVM)
  • spinal AVM

4.positive family history

definitive diagnosis:  ≥3
probable diagnosis:  2 criteria
diagnosis unlikely: < 2 criteria

 Diagnostic evaluation


  • good screening method to detect right-sided shunt (usually a massive shunt is present)

Contrast transthoracic echocardiography (cTTE)

  • recommended as the screening test of choice for PAVMs in HHT – sensitivity 94-100%, specificity 80%
  • after administration of agitated saline solution, microbubbles typically appear in the atrium within 3-8 cardiac cycles
    • in septal shunts, contrast is visible almost immediately
  • grading (significant association between TTCE grade and presence of PAVMs on CT was found)   [Zukotynski, 2007]
    • grade 1 – minimal opacification of the left ventricle
    • grade 2 – moderate opacification
    • grade 3 – extensive opacification without endocardial outlining
    • grade 4 – extensive opacification with endocardial definition


  • non-contrast +/- contrast-enhanced   Pulmonary arteriovenous malformation (PAVM) on CT angiography Pulmonary arteriovenous malformation (PAVM) on MR angiography (Schneider, 2008)
  • CE-MRA is suitable for screening; it enables accurate detection and staging of pulmonary AVMs, and differentiates lesions requiring embolization
    • limitations exist in detecting PAVMs <5 mm
  • CT
    • high sensitivity (comparable to DSA)
    • use of thin-slice (2-3 mm) non-contrast CT with 3-D reconstruction is recommended
    • the benefit of performing a contrast-enhanced CT pulmonary angiogram must be weighed against the risk of introducing air, leading to paradoxical embolism
Pulmonary A-V malformation on CTA

Digital subtraction angiography

  • the gold diagnostic standard  Pulmonary arteriovenous malformation (PAVM) on DSA
    • however, CTA seems to have a higher sensitivity (83%) compared to DSA (68%) but with slightly lower specificity
  • DSA remains a critical component in the treatment of PAVMs (embolization)

Chest X-ray

  • an initial imaging modality for patients presenting with hypoxemia or hemoptysis
  • chest X-ray has low sensitivity (70%) and is not ideal for screening
  • non-specific soft tissue mass with uniform density can be detected in larger PAVMs


  • therapy targets:
    • prevent neurological complications
    • prevent pulmonary hemorrhage
    • improve hypoxemia, which can lead to fatigue, weakness, and other health problems
  • indications for invasive management:
    • progressive PAVM growth (which indicates an increasing risk of complications)
    • paradoxical embolization (when blood clots or other debris travel through the PAVMs to the brain, causing strokes)
    • symptomatic hypoxemia
    • feeding vessels ≥3 mm
  • no specific medical treatment

Endovascular treatment

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Surgical treatment

  • lobectomy or pneumonectomy are rarely performed
  • thoracoscopic procedures are preferred, especially in short-feeding arteries with an increased risk of coil migration

Thrombolysis in patients with PAVM


  • lifetime antibiotic prophylaxis is recommended for surgical and dental procedures
  • extreme caution is necessary during intravenous administrations to prevent air embolism
  • in patients with known untreated PAVM, a follow-up CT scan every 2-3 years and annual oximetry are advised
  • exclude cerebral AVM (CAVM) in patients with PAVM; evaluation of hepatic AVM is not routinely performed
  • annual follow-ups are performed after endovascular treatment
  • screening in offspring of parents with HHT includes:
    • pulse oximetry every 1-2 years
    • O2 saturation < 97% warrants a TTE
    • in the presence of TTE abnormalities, a chest CT is indicated

Antithrombotic medication in stroke prevention

  • in HHT patients, antithrombotic therapy is not absolutely contraindicated; however, careful monitoring is required  [Gaetani, 2020] [Garg, 2014]
    • higher risk of bleeding is associated with anticoagulant therapy
  • after a stroke or myocardial infarction, the benefit of antiplatelet therapy is likely to outweigh the risk of bleeding

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Pulmonary A-V malformation
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