Pulmonary arteriovenous malformations (PAVMs) are abnormal connections between the pulmonary arteries and the pulmonary veins.  They are usually congenital. However, they can be caused by a variety of conditions, such as trauma, cirrhosis of the liver and HHT.

Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is a chromosomal disorder. Problems are caused by the growth of vascular malformations in a range of organs, most commonly the skin, throat, gastrointestinal tract, lungs, and brain.

Approximately 70% of PAVM cases are associated with HHT.  PAVMs and HHT are congenital but usually do not show until adulthood.

Telangiectasia and AVMs are abnormal vascular structures that occur in HHT. Telangiectasia is enlargement of the small blood vessels that carry the blood from the capillaries to the veins. AVMs are much larger lesions than those of telangiectasia, which consist of direct connections of the pulmonary artery to the pulmonary vein.

PAVMs can be classified as simple or complex types by their structure. Simple PAVMs have a single feeding artery leading to single draining pulmonary vein.  Complex PAVMs have two or more feeding arteries or draining veins.