Chronic Thromboembolic Pulmonary Hypertension

To understand this condition, it is important to understand the role of the pulmonary circulation. It is also helpful to understand the key words associated with the condition.

The Pulmonary Circulation

The pulmonary circulation is made up of the blood vessels that carry oxygen-rich blood through the lungs (the pulmonary system). As the blood flows though the lungs, it loads up with oxygen and loses the carbon dioxide it is carrying. Then, the oxygen-rich blood returns to the heart through the left upper chamber (atrium), flows into the left lower chamber (ventricle) and out through the aorta to all cells in the body.

Once the oxygen is lost from the blood, the veins carry it back to the heart from all over the body. It flows into the heart’s right atrium. After the atrium is filled with blood, it squeezes (contracts) and sends the blood into the right ventricle. When the right ventricle fills and contracts, it pushes blood into the pulmonary artery. The pulmonary artery goes into the lungs through the pulmonary circulation.

Key Words

Chronic is a medical term that describes a disease or condition that continues for a period of months or years.

A Pulmonary Thromboembolism refers to the clots that travel from veins in the body (emboli) and clog the arteries in the lungs. Once lodged in the lung arteries, they can cause more clots to form (thrombosis) and add more resistance to the blood flow through the lung.

This increased resistance from the clots increases the pressure inside the lungs. The medical term for increased pressure is Hypertension. Combining these key words gives us the meaning of chronic thromboembolic pulmonary hypertension: High blood pressure in the pulmonary arteries that lasts six months or longer. The condition often happens after there is a pulmonary embolism.

What causes CTEPH?

When the body cannot resorb a pulmonary embolism (PE), it can trigger CTEPH. However, up to half of all patients with CTPEH do not have a history of PE. In 2008, the World Council on Pulmonary Embolism reported that approximately 2 to 4 percent of people with PE develop CTEPH. It is a relatively rare disease. Only about 5,000 people in the United States are diagnosed with CTEPH each year. Because many patients with CTEPH have no history of PE, or don’t know they have PE, it can be overlooked or not suspected.

Risk factors for PE and CTEPH

Risk factors for pulmonary embolism include:

• Long periods of inactivity. This can include bed rest due to surgery or illness, or even a long trip by car or plane.
• Certain types of surgery, such as joint replacement of the hip or knee
• Older age
• Certain diseases, including peripheral artery disease, heart disease and cancer
• Family or personal history of blood clots
• Smoking
• Obesity
• A history of taking synthetic estrogen in the form of birth control pills or hormone replacement therapy

The risk factors for developing CTEPH include:

• Large PE or more than one episode of PE
• Previous surgical removal of the spleen
• Chronic inflammatory diseases, such as inflammatory bowel disease and osteomyelitis
• History of cancer
• Female sex
• Hypercoagulability disorders

What are the symptoms of CTEPH?

Many people who develop pulmonary hypertension after PE go through a so-called “honeymoon period” when they do not have any symptoms. When symptoms develop, they are vague and non-specific in the early stages of the disease. These include:

• Shortness of breath with exercise
• Chest discomfort
• Fatigue

Symptoms of later-stage disease include fainting and signs of right heart failure, such as fluid retention (edema) and blue-tinged fingers and toes (cyanosis).

Some patients with CTEPH never have any early symptoms. Most times, the disease is discovered in these patients when they develop late-stage symptoms or during an autopsy.

How is CTEPH diagnosed?

If a physician suspects a patient has CTEPH, the next step is to perform imaging studies and specialized tests. These may include:

• Transthoracic echocardiogram (TTE) – an ultrasound of the heart. TTE is used to screen for pulmonary hypertension.
• Ventilation-perfusion (V/Q) scan - radioactive material (radioisotopes) is injected to how well air moves through the lungs and how well the blood circulates through the lungs. In most cases, a normal result from a V/Q scan means the patient does not have CTEPH.
• Pulmonary angiography – X-rays that show blood flow through the lungs. This test is used to confirm a diagnosis of CTEPH after the patient has an abnormal V/Q scan. The combination of a V/Q scan and pulmonary angiography is considered the “gold standard” for diagnosing CTEPH.
• Heart catheterization - checks blood pressure and flow in the heart’s arteries and chambers. At Cleveland Clinic, a heart catheterization is a routine part of the diagnostic work-up for patients with any type of pulmonary hypertension.
• Computed tomography (CT) pulmonary angiography – a specialized type of CT scan that shows visual “slices” of the pulmonary arteries and gives more details about their physical condition. This test also shows visual “slices” of the lung tissue to help the physician determine the health of the tissue.
• Pulmonary function tests – used to make sure the lung tissue is not significantly diseased.

How is CTEPH treated?

A surgical procedure called a pulmonary thromboendarterectomy is currently the recommended and only effective treatment for patients with CTEPH. During this complex procedure, the surgeon cleans out the blockages in the pulmonary arteries in the right and left lungs using specialized tools. The surgery is performed through a chest incision while the patient’s heart is stopped. A heart-lung machine takes over the function of the heart and lungs during the procedure.

This surgery is considered a highly specialized procedure that should be performed only by an experienced team that includes cardiothoracic surgeons, anesthesiologists, perfusionists and intensivists at a medical center that has a successful track record with the procedure.

How well do patients do after the surgery?

When performed by an experienced team at a medical center with successful outcomes for this procedure, pulmonary thromboendarterectomy results in a complete cure in about 90 percent or more of patients. Success is measured by heart size and function and return of pulmonary blood pressure to normal limits. As surgical techniques and technology advance, outcomes continue to improve, and surgical mortality is now less than 3 percent.

Who can be considered for surgical treatment?

At Cleveland Clinic, all patients with CTEPH are screened and evaluated for possible pulmonary thromboendarterectomy. The decision to perform surgery is based on how severe the patients symptoms are, how high the pulmonary blood pressure is and abnormalities of the pulmonary circulation, whether the diseased areas in the pulmonary arteries can be reached during surgery, and the patient’s other medical conditions.

Patients with severe lung disease or disease of the heart’s left ventricle are not eligible for surgery. For patients who have coronary artery disease, coronary artery bypass grafting (CABG) surgery can be performed at the same time as the pulmonary thromboendarterectomy. Lung transplantation may be an option for some patients.

What are the potential risks or complications of pulmonary thromboendarterectomy?

About 10 percent of patients who have a pulmonary thromboendarterectomy continue to have pulmonary hypertension after the surgery. This condition causes about 75 percent of the deaths that occur within 30 days after surgery and 50 percent of deaths in the long-term. Studies show that patients who have pulmonary hypertension after the procedure were usually not good candidates for the surgery. This is because most of these patients have disease in small arteries that cannot be reached by the surgeon.

About 60 percent of patients develop fluid in the lungs after surgery. This is usually caused by slight injury to the lungs during surgery. The fluid goes away with time. For a small percentage of patients, the condition is severe enough to be life-threatening, and they may need ventilator support until the fluid is gone.

Is a medical treatment available for CTEPH?

Several different classes of drugs (prostanoids, endothelin receptor antagonists, phosphodiesterase-5 inhibitors) that are used for other types of pulmonary hypertension have been suggested as treatment of patients with CTEPH. To date, there has been only one randomized, controlled trial (the type of clinical study the U.S. Food and Drug Administration [FDA] requires for approval of a new treatment) to see how well these drugs work against CTEPH. The results of the trial were negative. Because there is no evidence of any benefit to patients with CTEPH, all these drugs are considered experimental and are not a suggested treatment.

At Cleveland Clinic, patients who are not candidates for surgery and those who develop pulmonary hypertension after surgery are treated with specialized medicines known to be effective against pulmonary hypertension .