Occasionally, these pulmonary AVMs are so large that they are visible on a plain chest x-ray (CXR). As depicted here, prominent vascular malformations can be identified in the right middle lobe adjacent to the right heart border. In addition to screening CXR and helical CT, contrast echo, using intravenous agitated saline injection can identify presence of pulmonary AVMs. Transit of agitated saline or 'bubbles' from the right-sided cardiac chambers to the left-sided chambers reliably demonstrates shunting through AVMs in the pulmonary vasculature. Treatment for these AVMs includes coil embolization, which occludes these abnormal connections and prevents future right-to-left embolization and cerebrovascular accidents.
Biology of HHT
Abnormalities in either the endoglin or activin-like kinase 1 (ALK-1) gene have been identified to cause HHT. Normally, these genes are involved in blood vessel development. Though HHT is inherited in a dominant fashion, the clinical manifestations can be extremely variable. Nosebleeds, gastrointestinal bleeding, pulmonary hemorrhage or cerebrovascular accidents (strokes) resulting from paradoxical right-to-left shunting and embolization of small venous thrombi are all common in patients with HHT, though variable within a particular family.
