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Pulmonary Arteriovenous Malformations (AVM)

What is a pulmonary arteriovenous malformation (AVM)?

Malformed connections between arteries and veins are referred to as aortovenous malformations (AVMs). In the lungs, larger arteries deliver blood to smaller arteries, which subsequently feed capillaries, the smallest blood vessels. Organ-specific capillaries slow down blood flow and enable the exchange of nutrients and gases between the blood and organs. Blood is transported from capillaries back to the heart through veins.

Because there are no capillaries between the arteries and veins in the presence of an AVM, there is less effective gas exchange, which lowers oxygen levels and increases shortness of breath, especially during physical exertion. An AVM's aberrant arteries and veins frequently have thin walls, which can lead to lung hemorrhage.  Through the AVM, clots or bacteria in the bloodstream of the lungs that would typically get stuck in tiny capillaries can reach the blood vessels of the brain and result in a stroke or a brain abscess.

Risk Factors

AVMs that develop as a result of a sickness like HHT (Hereditary Hemorrhagic Telangiectasia) might be lone or many.  Though the reasons are unknown, AVMs can appear throughout fetal development or soon after birth. AVMs of a particular type can develop following penetrating trauma, such as stab wounds or projectile wounds.  The majority of AVMs are not hereditary, although they can be a symptom of genetic disorders that are inherited, including HHT.

Symptoms

There are many pulmonary AVM patients that are asymptomatic, and symptoms might vary. Breathlessness may be experienced with bigger or many pulmonary AVMs, especially when exerting oneself. Brain infections or strokes can happen at any time. Blood may gather around the lung or coughed up due to an AVM that is bleeding.

Diagnosis

  • When a lung AVM is present, the microbubbles will pass through the AVM and be seen by the ultrasound during a "bubble study," which involves injecting tiny bubbles into an IV while an ultrasound scans the heart or outflow arteries.
  • If the bubble study is positive, a CT angiography can be performed to count and measure lung AVMs and evaluate whether treatment is necessary.
  • Angiography is a procedure that uses an X-ray and a contrast chemical to detect and treat faulty blood arteries.

Treatments

  • Pulmonary AVM embolization