PH and Hereditary Hemorrhagic Telangiectasia (HHT)
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My doctor says I have Hereditary Hemorrhagic Telangiectasia. What exactly does that mean?
Hereditary Hemorrhagic Telangiectasia (HHT) is a genetic disorder that causes abnormalities of blood vessels, usually resulting in excessive bleeding (known as hemorrhaging). In order to understand HHT, you must first understand the way blood is pumped to and from the heart. Blood vessels are hollow structures that transport blood throughout the body.
There are two types of blood vessels: arteries and veins. Arteries carry blood under high pressure away from the heart to all other areas of the body. Blood then passes through capillaries, where oxygen, nutrients and waste products can be exchanged. Veins carry blood that should be under low pressure back to the heart. An artery does not usually connect directly to a vein.
A person with HHT has a tendency to form blood vessels that lack capillaries between the arteries and veins, meaning that arterial blood under high pressure flows directly into a vein without first going through the very small capillaries. The site of this abnormal connection tends to be fragile and can rupture and result in bleeding.
This type of abnormal blood vessel is called a telangiectasia if it involves small blood vessels. It is called an arteriovenous malformation (AVM) if it involves large blood vessels. Telangiectases usually occur on the surface of the body, such as the skin and the mucous membranes that line the nose and the gastrointestinal tract. AVMs are found in the lungs, liver and central nervous system.
My doctor has asked me whether I feel lightheaded, out of breath or faint, and has said these might be symptoms of pulmonary hypertension. How does this relate to my HHT?
About 15 to 20 percent of people with HHT have at least mildly elevated pulmonary artery pressures, which means they either have or are developing PH. HHT patients can develop PH in two ways and the differences are significant.
In HHT-associated pulmonary arterial hypertension, abnormal blood flow through the blood vessels in the lungs causes elevated blood pressure. While it is not known exactly how many people have HHT-associated PAH, research has identified one affected member in 15 percent of families with a form of HHT known as HHT2. In another type of HHT, known as HHT1, HHT-associated PAH appears to be much less common.
More commonly, PH can develop in HHT patients as a result of increased blood flow from the heart, a condition called high cardiac output state. A high cardiac output state may be the result of several things, and a doctor may be able to determine the cause. Treatment will vary depending on what type of PH you have.
How do doctors test for this disease?
It is often difficult to detect PAH in HHT patients. In fact, some of the symptoms of PAH (fatigue, difficulty breathing and difficulty during physical exertion) are already found in people with HHT. To make things even more confusing, these symptoms are often seen in HHT patients as side effects of other health problems including heart failure, anemia and liver problems. Therefore, in many cases, a doctor must strongly suspect PAH, or it may go overlooked.
An echocardiogram can test for abnormally high blood flow in the lungs of HHT patients, and also can screen for PH. In addition, the echocardiogram provides important information about the heart, including its size and function. This test can also help uncover underlying problems the patient may be facing.
If PH is suspected in an HHT patient or diagnosed through an echocardiogram, another test, a right heart catheterization, can help doctors confirm it, and can also help to diagnose the exact type of PH the patient is suffering from.
What can be done for me?
Treatment is available; however, in order for a doctor to accurately treat HHT-associated PH, he or she must first diagnose the specific type of PH the patient has. If HHT-associated PAH is diagnosed, PAH specific therapies can be carefully prescribed, but these medications can also aggravate bleeding tendencies that are already present in HHT patients. As a result, HHT patients with PAH should seek out a specialist at a PH treatment center.