Hereditary hemorrhagic telangiectasia causes abnormalities of blood vessels, usually resulting in hemorrhaging.  

To understand how PH can develop, it is important to understand the way blood is pumped to and from the heart. Blood vessels transport blood throughout the body. There are three types of blood vessels: arteries, veins and capillaries.  

Arteries carry blood under high pressure away from the heart to other areas of the body. Blood then passes through capillaries — small blood vessels where oxygen, carbon dioxide, nutrients and waste products can be exchanged.  

Veins carry blood under low pressure back to the heart. An artery usually doesn’t connect directly to a vein without first passing through capillaries.  

With HHT, the capillaries can be missing between the arteries and veins, so arterial blood under high pressure flows directly into a vein. The site of the abnormal connection tends to be fragile and can rupture, causing bleeding.  

The abnormal blood vessel is called a telangiectasia if it involves small blood vessels. It is called an arteriovenous malformation if it involves large blood vessels.  

Telangiectasias usually occur on the body’s surface, such as the skin and mucous membranes that line the nose and gastrointestinal tract. Arteriovenous malformations are found in the lungs, liver and central nervous system.  

About 13 percent of people with HHT have at least mildly elevated pulmonary artery pressures.  

HHT-associated PH can develop in two ways, and the differences are significant. These two forms of HHT-associated PH are managed very differently.  

High-output heart failure

Most commonly, PH develops in HHT patients as a result of increased blood return to the heart due to large liver arteriovenous malformations. That leads to a condition known as high-output heart failure and is related to Group 2 PH.

In this situation, the arteries of the lungs are dilated (widened), and resistance to blood flow is low. But pressures are mildly elevated because of increased blood flow through the lungs and high pressures downstream from the lungs in the left side of the heart.

Anemia, which is common in HHT, will further worsen this type of heart failure and PH.

Group 2 PH

Heritable PAH

HHT can sometimes cause a form of heritable pulmonary arterial hypertension or Group 1 PH. Abnormally narrowed blood vessels hinder blood flow through the lungs, causing pressure in the arteries to rise significantly.

HHT-associated PAH is quite rare and estimated to occur in less than 1 percent of HHT patients, primarily in people with mutations in the ACVRL1 gene (formerly known as ALK1).

Group 1 PH

Diagnosing PH

PH is often difficult to detect in people with HHT. In fact, some symptoms of PH (fatigue and difficulty breathing, especially with physical activity) often develop in people with HHT because of other health conditions. Those conditions include heart failure, anemia and liver problems. Unless a doctor strongly suspects PH, it might be overlooked. Diagnostic tests may include:

  • Echocardiogram
  • Pulmonary function tests
  • Ventilation-perfusion (V/Q) scan
  • Natriuretic peptide tests
  • Right heart catheterization

Treatment options 

Treatment is available for HHT-associated PH. However, to accurately treat HHT-associated PH, doctors first must determine the specific type of PH.  While most patients will fall into Group 2 or Group 5, very rarely, a patient with HHT might have PH that falls into Group 4, related to organized blood clots in the lungs. 

High output heart failure treatment 

When PH is caused by high output heart failure, doctors should focus on:  

  • Treating heart failure with diuretics (water pills). 
  • Correcting anemia.  

Possibly providers may use anti-angiogenic therapy administered by an HHT expert to decrease the size of vascular liver malformations and slow the return of blood to the heart. 

PAH-specific therapies  

PAH therapies can be used carefully for heritable PAH, but those medications can aggravate bleeding, a problem for many people with HHT. People with HHT-associated PH should seek specialist care from PH centers that will collaborate with HHT experts.  

  • What Is Pulmonary Hypertension?

    Pulmonary hypertension, or high blood pressure in the pulmonary arteries, refers to a serious and complex condition in which the blood vessels in the lungs become stiff and narrow, putting strain on the right side of the heart.

  • Diagnosing Pulmonary Hypertension

    Common symptoms, many causes and a variety of tests can make pulmonary hypertension difficult to diagnose. Knowing what symptoms to look for and diagnostic tests that provide critical information can lead to an earlier diagnosis and better outcomes.

  • Treatments

    Treatments for pulmonary hypertension include targeted medical therapies, surgeries and other procedures, and supportive therapies such as oxygen or drugs that improve the function of the heart and lungs.

  • Find Expert Care

    All PH specialists on the list are members of PHA’s Pulmonary Hypertension Clinicians and Researchers membership network.

Additional Resources

Download or order a brochure

Information on PH and hereditary hemorrhagic telangiectasia is one of a series of PH& brochures available to download as a PDF or to order as a printed brochure. 

PH & HHT