Makindo Medical Notes

Related Subjects: |Pulmonary Stenosis |Pulmonary Regurgitation |Pulmonary Hypertension |Pulmonary Embolism

🫁 Introduction

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.