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Pulmonary Arteriovenous malformation
Related Subjects: |Pulmonary Stenosis |Pulmonary Regurgitation |Pulmonary Hypertension |Pulmonary Embolism |Dural Arteriovenous Malformations |Pulmonary Arteriovenous malformation |Sturge Weber syndrome
Pulmonary arteriovenous malformations (PAVMs) are abnormal direct connections between pulmonary arteries and veins, bypassing the normal capillary bed. This creates a right-to-left shunt ➝ deoxygenated blood enters systemic circulation without gas exchange. Consequences include hypoxemia, risk of paradoxical embolism (stroke, brain abscess), and haemoptysis. 🚨
📊 Epidemiology
- Prevalence ≈ 2–3 per 100,000 people (rare).
- 🧬 50–70% occur in Hereditary Hemorrhagic Telangiectasia (HHT).
- Slightly more common in women.
⚙️ Etiology & Pathophysiology
- 🧬 HHT (Osler-Weber-Rendu): Autosomal dominant; mutations in ENG, ACVRL1. Telangiectasias & AVMs in multiple organs (lungs, liver, brain).
- ❓ Idiopathic: No clear cause, minority of cases.
- 📉 Acquired:
- Hepatic cirrhosis (↑ pulmonary flow + angiogenic factors).
- Trauma / surgery (rare).
- Chronic infections (e.g., schistosomiasis).
🩺 Clinical Features
- 😮💨 Dyspnoea, hypoxemia ± cyanosis.
- 👆 Digital clubbing (chronic hypoxemia).
- 🤧 Epistaxis (esp. with HHT).
- 🧠 Neuro complications:
- Stroke (paradoxical embolus).
- Brain abscess (bacteria bypass filtration).
- Risk ≈ 1–2%/yr if untreated.
- 🫀 Haemoptysis, haemothorax (rupture).
- ❤️ High-output heart failure (large/multiple PAVMs).
- 🎧 Pulmonary bruit sometimes audible.
🔎 Diagnosis
- 📷 CXR: Well-defined lower lobe nodule/mass (can be normal).
- 💉 Contrast echocardiography (bubble study): Bubbles in LA after a few cycles = intrapulmonary shunt.
- 🫀 TEE: Rules out intracardiac shunts.
- 🖥 CT Pulmonary Angiography (CTPA): Gold standard – defines size, feeding artery, number.
- 🧲 MRI: Occasionally used for additional details.
- 🩸 ABG: Hypoxemia + ↑ A–a gradient.
- 🧬 Genetic testing: For suspected HHT.
🧾 Differential Diagnosis
- Intracardiac shunts (ASD, PFO).
- Pulmonary embolism.
- Bronchiectasis.
- Lung cancer.
- Pulmonary sequestration.
- Other cyanotic/hypoxemic disorders.
⚕️ Management
- 🎯 Goal: Prevent stroke, brain abscess, haemorrhage.
- 🩻 Transcatheter embolization (first-line): Coils or plugs to occlude feeding arteries; safe & effective.
- 🩺 Surgical resection: For non-embolizable lesions or complications (lobectomy/segmentectomy).
- 🧬 HHT management: Screening of relatives, AVM search in brain/liver, manage epistaxis/bleeds.
- 💉 Preventive measures:
- Air filters on IV lines to avoid air emboli.
- Antibiotic prophylaxis for procedures (controversial, but often used in high-risk cases).
- 🔁 Follow-up: Lifelong imaging; repeat embolization may be needed due to recanalization or new AVMs.
📈 Prognosis
With treatment (embolization), outcomes are generally excellent ✅. Oxygenation improves, risk of neuro complications falls. Untreated ➝ risk of paradoxical embolism and haemorrhage remains high. Patients with HHT require lifelong monitoring.
📚 References
- Shovlin CL et al. British Thoracic Society Clinical Statement on Pulmonary AVMs. Thorax. 2017.
- Faughnan ME et al. International Guidelines for Diagnosis & Management of HHT. J Med Genet. 2011.
- Guttmacher AE et al. Hereditary Hemorrhagic Telangiectasia. N Engl J Med. 1995.
- Meier NM et al. Diagnosis & Management of PAVMs. Curr Treat Options Cardiovasc Med. 2018.