5 Types of Pulmonary Hypertension

Pulmonary hypertension (PH) is a serious illness that is defined by higher than normal pressure in the pulmonary artery. Pulmonary hypertension causes dizziness, fainting, shortness of breath, chest pain, fatigue, and heart palpitations. Over time it leads to right heart failure.

It is helpful to understand some basic things about the circulatory system to see how pulmonary hypertension may occur. The left side of the heart, which is the larger side, pumps blood rich in oxygen to the rest of the body. After the oxygen is picked up by other tissues and organs in the body the oxygen-poor blood is returned to the right side of the heart. The right side of the heart then pumps this blood back to the lungs to pick up more oxygen.

Pulmonary hypertension occurs when the pressure required to carry blood through the lungs to pick up more oxygen exceeds 25 millimeters of mercury (mmHg) .

There are numerous different causes for this. As a result, pulmonary hypertension has been categorized into five types by the World Health Organization (WHO). Learn what sets each apart.

Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) may also be called primary pulmonary hypertension. This is WHO group 1.

Pulmonary arterial hypertension occurs due to a decrease in the diameter of the pulmonary arteries. This narrowing may be a result of stiffness, hardness, or a thickening of the arterial wall. The result is an increase in the amount of pressure required to pump blood through these narrowed blood vessels. Over time lesions develop inside of these blood vessels further inhibiting the amount of blood flow.

This type of pulmonary hypertension is more common in women ages 30-60 years.

There are multiple subtypes of PAH which include:

Idiopathic PAH

This is PAH that occurs in the absence of an identifiable cause.

Heritable PAH

Pulmonary arterial hypertension can be inherited. This familial type of PAH is usually associated with mutations in the BMPR2 gene although other genes have also been implicated. Approximately 15-20% of people with PAH inherited it.

Anorexigen Induced PAH

This type of pulmonary hypertension has been associated with the use of diet pills, specifically, dexfenfluramine (Redux) and fenfluramine (Pondimin). These appetite suppressants have been removed from the market. Another diet pill that was used in Europe, benfluorex, has also been associated with PAH, as have amphetamines and dasatinib.

Other Illnesses Associated with PAH

Several illnesses have been linked with the development of this type of pulmonary hypertension including:

  • Connective tissue diseases (scleroderma, lupus, etc.)
  • HIV/AIDS
  • Liver disease
  • Congenital heart disease
  • Diseases of the bone marrow or blood
  • Parasitic worms

There is currently no cure for pulmonary arterial hypertension. Medications such as prostaglandins (epoprostenol sodium) may prolong and improve the quality of life for individuals with PAH.

Pulmonary Hypertension Due to Left Heart Disease

Pulmonary hypertension due to left heart disease may also be referred to as secondary pulmonary hypertension or pulmonary venous hypertension (PVH). This is WHO group 2. This is the most common type of pulmonary hypertension.

This type of pulmonary hypertension has a totally different underlying pathology than that of PAH. Pulmonary hypertension due to left heart disease occurs when the left side of the heart is too weak to pump adequately and a backup occurs in the circulatory system. This backup subsequently causes the pressure in the lungs to increase. It is thought that after a period of time this leads to a change in the vasculature (blood vessels) supplying blood to the lungs.

This usually occurs when left-sided heart failure has progressed to an advanced stage of illness. Individuals who develop PVH may have experienced systemic high blood pressure for many years.

Although this type of pulmonary hypertension is the most common type, its underlying pathology is poorly understood and therefore treatment is usually reserved to addressing the left-sided heart failure with medications such as diuretics, or drugs to reduce systemic blood pressure like ACE inhibitors or beta blockers. There is some argument that more targeted therapies, like the drug sildenafil could be beneficial in treating PVH.

Pulmonary Hypertension Due to Lung Disease

Diseases which affect the lungs can lead to pulmonary hypertension. This is WHO group 3. The most common lung disease that leads to pulmonary hypertension is chronic obstructive pulmonary disease (COPD). However, it can also be caused by sleep apnea, emphysema, interstitial lung disease, pulmonary fibrosis or even living at very high altitudes for a significant period of time. 

People in this group experience low oxygen levels over a prolonged period which leads to a change in the vasculature that supplies blood to the lungs (probably the capillaries and arteries). It is thought that the arteries, specifically, tend to constrict or become tighter in an effort to restrict blood flow to the areas of the lungs that have the most oxygen. This constriction increases the overall blood pressure required to pump blood through the lungs.

Like PVH this type of pulmonary hypertension is often treated by addressing the underlying lung disease and hypoxia.

Pulmonary Hypertension Caused by Blood Clots in the Lungs

WHO group 4 consists of people who develop pulmonary hypertension as a result of chronic blood clots (pulmonary emboli) in their lungs. This is also called thromboembolic pulmonary hypertension (CTEPH). This is the only type of pulmonary hypertension that has the potential to be cured without a heart and lung transplant.

In individuals with this type of pulmonary hypertension the blood clots in their lungs turn into scar tissue in the blood vessels after a period of time, narrowing the diameter of these vessels, and blocking or decreasing the flow of blood to the lungs. It is also possible that like in PAH a remodeling of the small blood vessels that supply blood to the lungs occurs.

Most individuals who experience pulmonary emboli respond to blood-thinning medications but approximately 0.5-5% may go on to develop CTEPH. Individuals who have underlying clotting disorders may be at an increased risk.

Some patients with CTEPH may be candidates for an IVF filter. This tiny wire mesh filter is placed into the inferior vena cava and prevents new blood clots from getting to the lungs. Thromboembolic pulmonary hypertension may be treated surgically in some cases. This surgery is called a thromboendarterectomy.

A thromboendarterectomy is a high-risk surgery that is only performed at certain specialized hospitals throughout the U.S. by physicians who are specially qualified. During a thromboendarterectomy you are placed on a heart and lung machine which circulates your blood by bypassing your heart and lungs. An incision is made in your chest so that the surgeon can access your heart and lungs.

At a certain point in the procedure, your body will be cooled significantly and the heart and lung machine is stopped for a time so that the doctor can visualize and remove the clots from your pulmonary arteries. The gradual cooling of your blood to 65 F helps to prevent organ damage while the heart and lung machine is off. After the clots have been removed you are gradually warmed back up. Usually, chest tubes are inserted to help fluid from the lungs drain during the recovery period.

Following surgery you will likely need to stay in an intensive care unit (ICU) on a ventilator to help you breathe for a day or two. You may spend several days after that in the hospital. Even after discharge, it will probably take several months for you to really start feeling better and longer than that before you make a full recovery.

Pulmonary Hypertension Due to Miscellaneous Causes

The remaining group, WHO group 5, is somewhat of a catchall for anyone who has pulmonary hypertension and doesn't fit into the other 4 groups. Often the cause of pulmonary hypertension in this group cannot be identified but sometimes it can be associated with the following conditions:

Diagnosing Pulmonary Hypertension and Identifying the Type

Because the symptoms of pulmonary hypertension are vague and overlap with many other health conditions some patients with pulmonary hypertension may go many years before receiving a proper diagnosis. Many tests may be used leading up to an actual diagnosis including:

  • Blood tests to look at oxygen levels, kidney or liver function, and more
  • Chest X-rays (which may show enlargement of the right heart)
  • Heart tests such as an electrocardiogram (EKG) or echocardiogram
  • Pulmonary function tests
  • Exercise tolerance tests
  • A nuclear scan to look for blood clots in the lungs

Based on the results of these tests or your patient history combined with your symptoms your doctor may suspect pulmonary hypertension. The standard test for identifying pulmonary hypertension is a procedure called a right heart catheterization.

A right heart catheterization is a minor surgical procedure usually performed in a hospital on a same-day surgery basis. You will be sedated and a catheter will be inserted into a vein in your neck or groin. The catheter is threaded up into your heart and once there can actually measure the pressure in your heart and lungs.

The results of a right heart catheterization can not only be used to determine if you have pulmonary hypertension but the results combined with your health history can also be used to determine what type of pulmonary hypertension you have.

Therapies for Pulmonary Hypertension

Pulmonary hypertension of any type is a serious condition that usually (with the exception of some patients in WHO group 4) cannot be cured. Treatments focus on improving quality of life while hopefully prolonging life as well.

It is important to find a doctor who specializes in the treatment of patients with pulmonary hypertension to get the best care.

The type of treatment you and your doctor decide on depends on multiple factors including the type of pulmonary hypertension you have as well as any other underlying health conditions that might be contributing to your illness. Explore the options that are currently available, depending the type of PH.

Vasodilator Studies

For people already diagnosed with pulmonary hypertension a vasodilator study can help to monitor the effectiveness of treatments. This study is a right heart catheterization with the combined administration of a medication which relaxes the pulmonary blood vessels. This test can also determine if you will benefit from a type of medication called a calcium channel blocker.

Traditional Medications

Some medications that are not specifically used for pulmonary hypertension may be beneficial in controlling symptoms. These include calcium channel blockers to decrease blood pressure, digoxin to increase the strength of the heart, or diuretics to remove excess fluids from the body.

While these medications may be used in all types they are very often used for WHO group type 2. Other medications that may be used include blood thinners (often used for WHO group type 4) or oxygen (all types).

Endothelin Receptor Antagonists

This is a class of medications that is usually given orally. Endothelin receptor antagonists prevent the blood vessels from narrowing by blocking Endothelin receptors. This class of medications includes:

  • Tracleer (bosentan)
  • Letairis (ambrisentan)
  • Opsumit (macitentan)

Phosphodiesterase Inhibitors 

Phosphodiesterase inhibitors stimulate the production of vasodilators by the lungs (chemicals which cause the dilation of blood vessels) and are also given orally. Medications in this drug class include:

Intravenous Medications

A few intravenous medications are available for pulmonary hypertension and work by vasodilation of the pulmonary blood vessels. These include:

  • Flolan or Veletri (epoprostenol)
  • Orenitram (treprostinil) which may also be given subcutaneously or inhaled

Inhalers

Inhaled medications such as iloprost may be used to relieve shortness of breath.

Heart and Lung Transplant

When other treatment options have been exhausted some patients with pulmonary hypertension may be eligible to receive a heart and lung transplant. While a heart and lung transplant may potentially cure pulmonary hypertension is a serious medical procedure with a significant risk of complications including the potential rejection of the donor organs.

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Article Sources

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