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Article title: NHLBI, Facts About Primary Pulmonary Hypertension: NHLBI
Hypertension is the medical term for an abnormally high blood pressure. Normal mean pulmonary-artery pressure is approximately 14 mm Hg at rest. In the PPH patient, the mean blood pressure in the pulmonary artery is greater than 25 mm Hg at rest and 30 mm Hg during exercise. This abnormally high pressure (pulmonary hypertension) is associated with changes in the small blood vessels in the lungs, resulting in an increased resistance to blood flowing through the vessels.
This increased resistance, in turn, places a strain on the right ventricle, which now has to work harder than usual against the resistance to move adequate amounts of blood through the lungs.
Between 1967 and 1973, a 10-fold increase in unexplained pulmonary hypertension was reported in central Europe. The rise was subsequently traced to aminorex fumarate, an amphetamine-like drug introduced in Europe in 1965 to control appetite. Only about 1 in 1,000 people who took the drug developed PPH. When they stopped taking the drug, some improved considerably; in others, the disease kept getting worse. Once aminorex was removed from the market, the incidence of PPH went down to normal levels.
More recently, in the United States and France, several cases of PPH have been associated with the appetite suppressants, fenfluramine and dexfenfluramine.
In the United States it has been estimated that 300 new cases of PPH are diagnosed each year; the greatest number are reported in women between the ages of 21 and 40. Indeed, at one time the disease was thought to occur among young women almost exclusively; we now know, however, that men and women in all age ranges, from very young children to elderly people, can develop PPH. Apparently it also affects people of all racial and ethnic origins equally.
Researchers think that in most people who develop PPH the blood vessels are particularly sensitive to certain internal or external factors and constrict, or narrow, when exposed to these factors. For example, people with Raynaud's disease seem more likely than others to develop PPH; Raynaud's disease is a condition in which the fingers and toes turn blue when cold because the blood vessels in the fingers and toes are particularly sensitive to cold. Diet suppressants, cocaine, HIV, and pregnancy are some of the factors that are thought to trigger constriction, or narrowing, in the pulmonary artery.
In about 6 to 10 percent of cases, PPH is familial; that is, it is inherited from other family members. The familial form of PPH is similar to the more common form of the disease, sometimes referred to as "sporadic" PPH.
|Normal small pulmonary artery with typically thin muscular wall.|
|Some of the changes that can occur in primary pulmonary hypertension:|
|Wall of small pulmonary artery thickens.|
|Fibrous, or scarred, tissue appears on inner wall of small pulmonary artery.|
|Bands of scarred tissue build up on inner wall of small pulmonary artery, substantially narrowing the blood vessel.|
The process eventually results in the development of extra amounts of tissue in the walls of the pulmonary arteries. The amount of muscle increases in some arteries, and muscle appears in the walls of arteries that normally have no muscle. With time, scarring, or fibrosis, of the arteries takes place, and they become stiff as well as thickened. Some vessels may become completely blocked. There is also a tendency for blood clots to form within the smaller arteries.
In response to the extra demands placed on it by PPH, the heart muscle gets bigger, and the right ventricle expands in size. Overworked and enlarged, the right ventricle gradually becomes weak and loses its ability to pump enough blood to the lungs. Eventually, the right side of the heart may fail completely, resulting in death.
The first symptom is frequently tiredness, with many patients thinking they tire easily because they are simply out of shape. Difficulty in breathing (dyspnea), dizziness, and even fainting spells (syncope) are also typical early symptoms. Swelling in the ankles or legs (edema), bluish lips and skin (cyanosis), and chest pain (angina) are among other symptoms of the disease.
Patients with PPH may also complain of a racing pulse; many feel they have trouble getting enough air. Palpitations, a strong throbbing sensation brought on by the increased rate of the heartbeat, can also cause discomfort.
Some people with PPH do not seek medical advice until they can no longer go about their daily routine. The more severe the symptoms, the more advanced the disease. In these more advanced stages, the patient is able to perform only minimal activity and has symptoms even when resting. The disease may worsen to the point where the patient is completely bedridden.
PPH remains a diagnosis of exclusion. This means that it is diagnosed only after the doctor finds pulmonary hypertension and excludes or cannot find other reasons for the hypertension, such as a chronic obstructive pulmonary disease (chronic bronchitis and emphysema), blood clots in the lung (pulmonary thromboemboli), or some forms of congenital heart disease.
The first tests for PPH help the doctor determine how well the heart and lungs are performing. If the results of these tests do not give the doctor enough information, the doctor must perform a cardiac catheterization. The procedure, discussed below, is the way the doctor can make certain that the patient's problems are due to PPH and not to some other condition.
The electrocardiogram (ECG) is a record of the electrical activity produced by the heart. An abnormal ECG may indicate that the heart is undergoing unusual stress.
In addition to the usual ECG performed while the patient is at rest, the doctor may order an exercise ECG. This ECG helps the doctor evaluate the performance of the heart during exercise, for example, walking a treadmill in the doctor's office.
In an echocardiogram, the doctor uses sound waves to map the structure of the heart by placing a slim device that looks like a microphone on the patient's chest. The instrument sends sound waves into the heart, which then are reflected back to form a moving image of the beating heart's structure on a TV screen. A record is made on paper or videotape. The moving pictures show how well the heart is functioning. The still pictures permit the doctor to measure the size of the heart and the thickness of the heart muscle; in the patient with severe pulmonary hypertension, the still pictures will show that the right heart is enlarged, while the left heart is either normal or reduced in size. Echocardiograms are helpful in excluding some other causes of pulmonary hypertension and can be useful in monitoring the response to treatment.
A variety of tests called pulmonary function tests (PFTs) evaluate lung function. In these procedures, the patient, with a nose clip in place, breathes in and out through a mouthpiece. The patient's breathing displaces the air held in a container suspended in water. As the container rises and falls in response to the patient's breathing, the movements produce a record, or spirogram, that helps the doctor measure lung volume (how much air the lungs hold) and the air flow in and out of the lungs. Some devices measure air flow electronically.
A mild restriction in air movement is commonly seen in patients with PPH. This restriction is thought to be due, in part, to the increased stiffness of the lungs resulting from both the changes in the structure and the high blood pressure in the pulmonary arteries.
Two patterns of pulmonary perfusion are seen in patients with PPH. One is a normal pattern of blood distribution; the other shows a scattering of patchy abnormalities in blood flow.
A major reason for doing a perfusion scan is to distinguish patients with PPH from those whose pulmonary hypertension is due to blood clots in the lungs.
During catheterization, the doctor can also evaluate the right heart's pumping ability; this is done by measuring the amount of blood pumped out of the right side of the heart with each heartbeat.
Once PPH is diagnosed, most doctors will classify the disease according to the functional classification system developed by the New York Heart Association. It is based on patient reports of how much activity they can comfortably undertake.
Class 1--Patients with no symptoms of any kind, and for whom ordinary physical activity does not cause fatigue, palpitation, dyspnea, or anginal pain.
Class 2--Patients who are comfortable at rest but have symptoms with ordinary physical activity.
Class 3--Patients who are comfortable at rest but have symptoms with less-than-ordinary effort.
Class 4--Patients who have symptoms at rest.
Until recently, nothing more could be done for people who have PPH. However, today doctors can choose from a variety of drugs that help lower blood pressure in the lungs and improve the performance of the heart in many patients.
Some patients also require supplemental oxygen delivered through nasal prongs or a mask if breathing becomes difficult; some need oxygen around the clock. In severely affected cases, a heart-lung, single lung, or double lung transplantation may be appropriate.
To find out which medicine works best for a particular patient, doctors evaluate the drugs during cardiac catheterization. This way they can see the effect of the medicine on the patient's heart and lungs. They can also adjust the dose to reduce the side effects that may occur--for example, systemic low blood pressure (hypotension); nausea; angina; headaches; or flushing.
To determine whether a drug is improving a patient's condition, both the pulmonary pressure and the amount of blood being pumped by the heart (the cardiac output) must be evaluated. A decrease in pulmonary pressure alone, for example, does not necessarily mean that the patient is recovering; cardiac output must either increase or remain unchanged. The most desirable response is a decrease in pressure and an increase in cardiac output. Once the patient has reached a stable condition, he or she can go home, returning every few weeks or months to the doctor for followup.
At present, approximately one-quarter to one-half of patients can be treated with calcium channel blocking drugs given by mouth. By relaxing the smooth muscle in the walls of the heart and blood vessels, these calcium channel blockers improve the ability of the heart to pump blood.
A vasodilator, prostacyclin, is helping some severely ill patients who are unresponsive to treatment with calcium channel blockers. The drug, which has been studied in clinical trials, imitates the natural prostacyclin that the body produces on its own to dilate blood vessels. Prostacyclin also seems to help prevent blood clots from forming.
Prostacyclin is administered intravenously by a portable, battery-operated pump. The pump is worn attached to a belt around the waist or carried in a small shoulder pack. The medication is then slowly and continuously pumped into the body through a permanent catheter placed in a vein in the neck.
Protstacyclin seems to improve pulmonary hypertension and permit more physical activity. It is sometimes used as a bridge to help those patients waiting for a transplant, while in other cases it is used for long-term treatment.
The single lung transplant is the most common method of transplant used in cases of PPH. This procedure, in which one lung--either the left or right--is replaced, was first performed in 1983 in patients with pulmonary fibrosis. Double lung transplants are also done to treat PPH, but are less common than the single lung transplant for treatment of PPH.
There are fewer complications with the single lung transplant than with the heart-lung transplant, and the survival rate is on the order of 70 percent for 1 year. A surprising finding is the remarkable ability of the right ventricle to heal itself. In patients with lung transplants, both the structure and function of the right ventricle markedly improve. Complications of transplantation include rejection by the body of the transplanted organ, and infection. Patients take medications for life to reduce their body's immune system's ability to reject "foreign" organs.
In 1981, the National Heart, Lung, and Blood Institute (NHLBI) established the first PPH-patient registry in the world. The registry followed 194 people with PPH over a period of at least 1 year and, in some cases, for as long as 7.5 years. Much of what we know about the illness today stems from this study.
At the time the patients enrolled in the registry, 75 percent were in functional classes 3 or 4. They had an average mean pulmonary artery pressure three times the normal, an abnormally high pressure in the right side of the heart, and a reduced cardiac output. In making the diagnosis of PPH, investigators found no complications arising from cardiac catheterization.
The study findings show that pulmonary artery pressure in patients who had symptoms for less than 1 year was similar to that in patients who had symptoms for more than 3 years. Researchers also found that patients whose only symptom was difficulty in breathing upon exercise already had very high pulmonary artery pressure. This suggests that the pulmonary artery pressure rises to high levels early in the course of the disease.
No correlations could be found between the cause of PPH and cigarette smoking, occupation, place of residence, pregnancy, use of appetite suppressants, or use of prescription drugs, including oral contraceptives. This study was designed to serve only as a registry, so it was not possible to evaluate the effectiveness of treatment.
Because we still do not understand the cause or have a cure for PPH, NHLBI remains committed to supporting basic and clinical studies of this illness. Basic research studies are focusing on the possible involvement of immunologic and genetic factors in the cause and progression of PPH, looking at agents that cause narrowing of the pulmonary blood vessels, and identifying factors that cause growth of smooth muscle and formation of scar tissue in the vessel walls. Most important is finding a reliable way to diagnose PPH early in the course of the disease that does not require cardiac catheterization.
People with PPH go to school, work at home or outside the home part-time or full-time, and raise their children. Indeed, many patients with PPH do not look sick, and some feel perfectly well much of the time as long as they do not strain themselves physically.
Walking is good exercise for many patients. Some patients with advanced PPH carry portable oxygen when they go out; patients who find walking too exhausting may use a wheelchair or motorized scooter. Others stay busy with activities that are not of a physical nature.
For the patient who lives at a high altitude, a move to a lower altitude--where the air is not so thin, and thus the amount of oxygen is higher--can be helpful. Medical care is important, preferably by a doctor who is a pulmonary vascular specialist. These specialists are usually located at major research centers.
PPH patients can also help themselves by following the same sensible health measures that everyone should observe. These include eating a healthy diet, not smoking, and getting plenty of rest. Pregnancy is not advised because it puts an extra load on the heart. Oral contraceptives are not recommended, and other methods of birth control should be used.
Most doctors and patients agree that it is important for both patient and family to be as informed as possible about PPH. In this way everyone can understand the illness and apply that information to what is happening. In addition to family and close friends, support groups can help the PPH patient.
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