Pulmonary hypertension is characterized by high blood pressure (hypertension) in the blood vessels that supply oxygen-poor blood to the lungs. There are two forms of pulmonary hypertension: primary and secondary. Primary pulmonary hypertension (PPH) has no known cause and is relatively uncommon. It is sometimes called idiopathic pulmonary hypertension. Secondary pulmonary hypertension (SPH) is caused by an underlying heart condition, lung disease or pulmonary embolism (a blood clot that has become lodged in one or more of the pulmonary blood vessels). Secondary pulmonary hypertension has also been associated with the use of certain diet drugs, cocaine abuse and HIV infection.
Like all forms of high blood pressure, pulmonary hypertension requires treatment to reduce the risk of serious consequences. These consequences can include a leaking valve on the right side of the heart (tricuspid regurgitation) or complete right-side heart failure. In many cases pulmonary hypertension is not detected until after a diagnosis of right-sided heart failure.
Treatment for pulmonary hypertension includes lifestyle changes, medication and, in extreme cases, surgery.
About pulmonary hypertension
Pulmonary hypertension is characterized by high blood pressure (hypertension) in the pulmonary arteries that supply oxygen-poor blood to the lungs. There are a number of reasons this condition may result. For example, the blood vessels of the lung (pulmonary arterioles) may have narrowed, thus restricting blood flow through the lungs. Alternatively, the condition may be caused by heart disease of the left side of the heart, which causes blood to back up into the lungs, raising the blood volume in the pulmonary vascular bed.
Pulmonary hypertension is diagnosed by measuring the blood pressure in the pulmonary arteries. Under normal circumstances, mean pulmonary artery pressure at rest is about 14 mmHg (milimeters of mercury). Pulmonary hypertension is defined as a pulmonary artery blood pressure that is greater than 25 mmHg at rest or 30 mmHg during exercise. It is further classified by its underlying cause. Primary pulmonary hypertension (PPH) occurs with no known cause, whereas secondary pulmonary hypertension is due to another, identifiable factor.
Although PPH is rare, an estimated 500 to 1,000 new cases are diagnosed annually. The disease can occur in men, women and children of all ages. However, it is most common in females between 20 and 40 years old, with twice as many cases reported in women than men, according to the National Heart, Lung and Blood Institute. The condition is rare in children but is sometimes seen in infants who are born with a heart defect (congenital heart disease).
Secondary pulmonary hypertension (SPH), in which the high blood pressure is caused by another underlying condition, is much more common. Typical causes of SPH include:
Lung disease (e.g., chronic obstructive pulmonary disease [COPD] and lung fibrosis). COPD is the most common cause of SPH in adults.
Sleep apnea. This condition occurs when the upper airway becomes obstructed during sleep, resulting in poor oxygen flow. Untreated, this condition can lead to pulmonary hypertension. It is also associated with increased risk of cardiovascular disease.
Heart problem (e.g., congenital heart disease or mitral valve stenosis). An abnormally functioning left ventricle can also cause pulmonary hypertension. Other heart problems associated with pulmonary hypertension include heart failure, certain cardiomyopathies, constrictive pericarditis, or left-to-right shunts such as those caused by a ventricular septal defect.
Systemic connective tissue disease. These disorders are characterized by abnormalities in the connective tissue that provides structure to the body. Examples of this kind of disease are scleroderma and rheumatoid arthritis. Scleroderma is closely associated with Raynaud's phenomenon.
Neuromuscular diseases that affect the respiratory muscles, causing them to function abnormally and reducing the lung's ability to receive oxygen. Examples of such diseases include poliomyelitis, myasthenia gravis and amyotrophic lateral sclerosis (Lou Gehrig's disease).
Pulmonary embolism (a blood clot that has become lodged in a blood vessel in the lung).
Studies have shown that both primary and secondary pulmonary hypertension are linked to certain impaired genes. Both types can lead to serious cardiovascular problems if untreated.
The ability to cure pulmonary hypertension is related to the cause of the disease. There is no cure for primary hypertension, but in recent years, physicians have developed a number of approaches that can successfully manage the condition and improve the patient’s quality of life. Secondary pulmonary hypertension may be cured by treatment of the underlying condition. In either case, it is important to identify the condition as quickly as possible and seek out qualified treatment before permanent damage results to the lungs or the right side of the heart.
When pulmonary artery pressure becomes elevated, the right side of the heart has a harder time pumping blood through the narrowed pulmonary artery and to the lungs. Eventually, the continuous effort can cause the heart to become enlarged and weakened. Untreated pulmonary hypertension can lead to:
Regurgitation of the tricuspid valve. A leaking valve on the right side of the heart.
Cor pulmonale. Right-side heart failure.
It has also been shown that pulmonary hypertension increases the risks associated with some heart diseases. For example, individuals with myocarditis have significantly higher risks of mortality for each 5 mmHg increase in pulmonary blood pressure. In addition, these patients may be at a higher risk for endocarditis, which is an infection of the heart valves. To reduce the risk of endocarditis, some patients with pulmonary hypertension may be instructed to take antibiotics prior to dental procedures.
Signs and symptoms
Like other forms of high blood pressure (hypertension), there are no symptoms in the early stages of pulmonary hypertension. Also, the symptoms of pulmonary hypertension are often hidden by the underlying condition causing the disease. Symptoms tend to vary from patient to patient. They may include:
Fatigue or tiredness
Dizziness
Fainting (syncope)
Shortness of breath
Swelling (edema) in the ankles or feet
Bluish skin or lips (cyanosis)
Chest pain
Coughing (sometimes with blood)
Distended neck veins
Enlarged liver
Swollen abdomen
The symptoms that are most directly caused by pulmonary hypertension include fatigue, lethargy, breathlessness after exertion, chest pain and fainting after exertion.
Diagnosis methods for pulmonary hypertension
After the physician gives the patient a physical examination and asks about the patient's medical history, a number of tests may be ordered to aid in the diagnosis of pulmonary hypertension. These include:
Arterial blood gas studies. Blood is taken from an artery and analyzed for the amount of gases present, particularly oxygen.
Right-heart cardiac catheterization. A catheter is passed into the right ventricle of the heart and pulmonary artery, where it is used to obtain a precise measure of blood pressure and blood flow in those areas. The physician will also measure and evaluate the pumping ability of the right side of the heart. This test may be performed multiple times during treatment of confirmed pulmonary hypertension.
Right-sided hypertrophy (or inflation of the right ventricle) is a common complication of pulmonary hypertension. This may lead to elevated venous pressure, which occurs when the blood pressure in the veins throughout the body is raised.
Chest x-ray. This imaging test offers the physician a picture of the general size, shape and structure of the heart and lungs. One of the things the physician will check is whether the right side of the heart is enlarged.
Echocardiogram of the heart and major arteries. This test uses sound waves to track the structure and function of the heart. A moving image of the patient’s beating heart is played on a monitor, where a physician can study the heart’s thickness, size and function. The image also shows the motion pattern and structure of the four heart valves, revealing any potential leakage (regurgitation). A specific type of echocardiogram, called a Doppler ultrasound is sometimes used to determine pulmonary artery pressure.
Electrocardiogram (EKG). A test that measures the heart’s electrical activity. It is designed to detect any abnormal rhythms (arrhythmias), which may be signs that the heart or parts of the heart are overly stressed.
Perfusion lung scan. A test used to show the pattern of blood flow in the lung. The test involves the injection of a radiopharmaceutical into an arm vein before scanning the lung with a gamma camera. In the resulting picture, any sections of the lung in which blood is being restricted will show up as blank spaces. The test will also detect any large blood clots in the lungs.
Pulmonary angiogram. A test used to measure circulation in the lungs and to visualize clots in the lung on x-rays. The test involves the insertion of a thin catheter into the pulmonary artery through which an iodine dye is injected. The physician can then see an image of any blood clots present in the lung, and track the circulation of blood through the lung's blood vessels.
Pulmonary function test. A painless test in which the patient blows into a special device (a spirometer) that measures and evaluates how well the lungs are functioning.
Treatment options for pulmonary hypertension
There is currently no cure for pulmonary hypertension, although researchers continue to investigate treatments in the hope of finding a cure. In the meantime, successful management of the disease is possible. In cases of secondary pulmonary hypertension, the underlying cause (e.g., heart disease or another lung disease) will be the main focus of treatment.
Lifestyle changes are important. People with primary hypertension are often asked to stop taking all diet pills(especially those that suppress appetite), to avoid strenuous physical activity and to avoid being around people with respiratory infections. Short periods of regular exercise are recommended, but only when alternated with periods of rest to avoid over-exerting the lungs and heart. Eating a healthy diet is also important, including limiting salt and increasing the intake of antioxidant vitamins such as vitamin C, vitamin E and the trace mineral selenium.
Many patients with pulmonary hypertension are also put on oxygen therapy, especially among patients with chronic obstructive pulmonary disease (COPD). Additionally, although firm studies are lacking, patients with pulmonary hypertension caused by right ventricular dysfunction and other causes may be put on oxygen therapy.
Medications may also be prescribed to treat pulmonary hypertension. Because the responses to medications vary, physicians may try their patients on a few different types before a long-term therapy is formulated. In some cases, different medications may be administered during a cardiac catheterization so the physician can see their effects on blood vessels. Medications that may be used in the treatment of pulmonary hypertension include:
Epoprostenol. This medication is a potent vasodilator that is administered intravenously. Patients who do not respond to other medications (e.g., calcium channel blockers) may be outfitted with a permanent catheter and an intravenous pump to administer continuous epoprostenol. Studies have shown that this medication improves lung function among patients with both secondary and primary pulmonary hypertension.
Anticoagulants. Medications that inhibit the formation of blood clots. These are used to prevent blood clots from forming in the lungs, where the blood flow may be sluggish. They may also be prescribed among patients with secondary pulmonary hypertension that is due to one or more blood clots.
Calcium channel blockers. Medications that reduce the workload of the heart by blocking calcium ions from signaling the blood vessels to constrict or tighten. Calcium channel blockers are often prescribed for patients who respond to vasodilators. However, their effectiveness is highly variable among patients with pulmonary hypertension, and in some patients, they may worsen the condition.
Cardiotonics. Medications that strengthen the contractions of the heart so the heart does not need to beat as often in order to circulate an adequate amount of blood for the body.
Diuretics. Medications that promote the formation of urine by the kidneys, causing the body to flush out fluids and minerals. If the kidneys malfunction and do not rid the body of the excess fluid in the system, the increased volume of blood being pumped through the blood vessels can lead to high blood pressure (hypertension). Diuretics are usually prescribed for patients with advanced heart or lung disease as a result of their pulmonary hypertension, including right-sided heart failure.
Endothelin receptor antagonists. Medications that help increase blood supply to the lungs and, in so doing, reduce the workload of the heart. Bosanten, a type of endothelin receptor antagonist, is approved for use in the treatment of pulmonary hypertension.
Prostacyclins. Medications that both dilate blood vessels (vasodilators) and inhibit the formation of blood clots (anticoagulants). Traditionally used during kidney dialysis, prostacyclins have also become a useful tool in treating pulmonary hypertension. However, prostacyclins currently can be delivered only through a continuous intravenous infusion. Other methods of delivery, including an inhaled form, are being researched.
Phosphodiesterase (PDE) inhibitors. Medications that work by blocking an enzyme called phosphodiesterase (PDE) and facilitating the dilation of the blood vessels. Sildenafil PO is a common PDE inhibitor used to treat pulmonary hypertension.
A combination of medications, lifestyle changes and treatment of underlying conditions is usually enough to bring pulmonary hypertension under control. Surgical interventions, such as transplantation, are only considered in extreme cases. When lung transplantation and/or heart transplantation is necessary, the patient’s damaged organs are surgically replaced by healthy donated organs.
An experimental procedure called dilation atrial septostomy is being investigated for use in patients with severe pulmonary hypertension who are waiting for a heart and/or lung transplant. Dilation atrial septostomy involves making a small hole in the heart and slowly enlarging it to relieve some of the pressure in the heart’s right side by shunting blood across the atrial septum and into the left side of the heart. This procedure is similar to balloon atrial septostomy in which a naturally occurring hole present at birth is enlarged to help children with certain congenital heart defects. More research is necessary before this procedure can be useful as a “bridge to transplant” for patients with pulmonary hypertension.
Other areas of research for the treatment of pulmonary hypertension include stem cell research and gene therapy.
Prevention of pulmonary hypertension
Because the cause of primary pulmonary hypertension is unknown, there is no known strategy for preventing it. However, the best strategy for preventing secondary pulmonary hypertension is to avoid all tobacco smoke. It is also helpful to avoid the risk factors associated with pulmonary hypertension, which include:
Cocaine use
Exposure to air pollutants
HIV infection
Living at high altitudes
Obesity
Physical inactivity
Using certain diet drugs
In addition, some conditions are known to increase the risk of pulmonary hypertension (e.g., Raynaud syndrome, sickle cell anemia,scleroderma, COPD, Lou Gehrig's disease, rheumatoid arthritis). People diagnosed with such conditions are encouraged to discuss regular screening for pulmonary hypertension with their physician.
Role of pulmonary artery in circulation
The pulmonary artery carries oxygen–poor blood from the heart to the lungs. In the lungs, carbon dioxide (a waste product) is removed from the blood and exhaled from the body. The blood is then filled with vital oxygen that was inhaled from the air. From the lungs, the blood (now oxygen-rich) travels via the pulmonary veins back to the heart. The blood enters the upper left chamber of the heart (the left atrium) and passes through the mitral valve into the left ventricle. The left ventricle pumps the blood through the aortic valve, out the aorta and to the rest of the body.
Once the body has taken the oxygen from the blood and deposited carbon dioxide into the blood, the blood (now oxygen-poor) returns to the heart. It enters the upper-right chamber of the heart (the right atrium), and passes through the tricuspid valve into the right ventricle of the heart. The right ventricle of the heart then pumps the blood through the pulmonic valve (also known as the pulmonary valve), out the pulmonary artery and to the lungs to get more oxygen.
Questions for your doctor
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to pulmonary hypertension:
How serious is the blood pressure elevation in my lungs?
Is this condition caused by another, underlying problem?
Will treating the underlying condition relieve the elevated blood pressure in my lungs?
Is this a permanent condition? Will I need lifelong treatment?
Which of my symptoms are probably caused by pulmonary hypertension as opposed to any underlying conditions?
Should I start exercising? How much? How often? Can I safely have sex?
What medications should I take to help relieve the blood pressure in my lungs?
Will I need supplemental oxygen?
Are there any dietary supplements I should avoid? Any that I should take?
How often should I have my pulmonary blood pressure monitored?
If this condition continues to worsen, what other interventions might be necessary?
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