Minggu, Mei 20, 2012

Pulmonary Hypertension

What are pulmonary arteries?

The human body has two major sets of blood vessels that distribute blood from the heart to the body. One set pumps blood from the right heart to the lungs and the other from the left heart to the rest of the body.

  • The portion of the circulation that distributes oxygen-rich blood from the left side of the heart, throughout the body, is referred to as the systemic circulation.
  • The blood then returns from the body to the right side of the heart and passes through the lungs to replenish oxygen.
  • It then returns to the left side of the heart for another round through the systemic circulation.
  • The portion of the circulation that distributes the blood from the right side of the heart to the lungs is referred to as the pulmonary (lung) circulation.
  • The pulmonary arteries are the major blood vessels that carry blood from the right side of the heart to the lungs.

The left ventricle of the heart pumps oxygenated blood (blood that has been reloaded with oxygen in the lungs) from the lungs into the systemic circulation. When a doctor or a nurse measures the blood pressure on a person's arm, he/she is measuring the pressures in the systemic circulation. When these pressures are abnormally high, the person is diagnosed as having high blood pressure (hypertension).

What is pulmonary hypertension?

The right ventricle pumps blood returning from the body into the pulmonary arteries to the lungs to receive oxygen. The pressures in the lung arteries (pulmonary arteries) are normally significantly lower than the pressures in the systemic circulation. When pressure in the pulmonary circulation becomes abnormally elevated, it is referred to as pulmonary hypertension, pulmonary artery hypertension, or PAH.

Pulmonary hypertension generally results from constriction, or stiffening, of the pulmonary arteries that supply blood to the lungs. Consequently, it becomes more difficult for the heart to pump blood forward through the lungs. This stress on the heart leads to enlargement of the right heart and eventually fluid can build up in the liver and other tissues, such as the in the legs.

What are primary and secondary pulmonary hypertension?

In the conventional classification, pulmonary hypertension, which is also called pulmonary arterial hypertension, is divided into two main categories; 1) primary pulmonary hypertension (not caused by any other disease or condition); and 2) secondary pulmonary hypertension (caused by another underlying condition). Secondary pulmonary hypertension is much more common than primary pulmonary hypertension.

A newer classification of this condition is based on the main underlying cause of pulmonary hypertension. This system classifies the condition based on whether it is due to:

  • left sided heart disease,
  • lung disease,
  • blood clots,
  • constriction of arteries due to any reasons (including primary pulmonary hypertension), and
  • obstruction from outside of blood vessel (for example from diseases of the chest wall compressing the blood vessels).

What causes pulmonary hypertension?

Pulmonary hypertension can be caused by diseases of the heart and the lungs, such as:

Other conditions that may cause pulmonary hypertension include:

Pulmonary hypertension can also be caused by chronic low blood oxygen levels as in some patients with sleep apnea or other long-standing (chronic) lung disease.

Again, pulmonary hypertension caused by these other illnesses can also be referred to as secondary pulmonary hypertension.

When pulmonary hypertension occurs without underlying heart and lung disease or other illnesses, it is called primary pulmonary hypertension. Primary pulmonary hypertension is more common in younger people and more in females than in males.

Recently this condition has been rarely reported with the use of anti-obesity drugs such as dexfenfluramine (Redux) and Fen/Phen. These medications have seen been removed from the market. Some street drugs such as, cocaine and methamphetamines can cause severe pulmonary hypertension.

What causes primary pulmonary hypertension?

Primary pulmonary hypertension has no identifiable underlying cause. Primary pulmonary hypertension is also referred to as idiopathic pulmonary hypertension.

Primary pulmonary hypertension is an unusually aggressive and often fatal form of pulmonary hypertension that commonly affects young people. Whereas it is known that the arterial obstruction is caused by a building up of the smooth muscle cells that line the arteries, the underlying cause of the disease has long been a mystery.

A genetic cause of the familial form of primary pulmonary hypertension has been discovered. It is caused by mutations in a gene called BMPR2. BMPR2 encodes a receptor (a transforming growth factor beta type II receptor) that sits on the surface of cells and binds molecules of the TGF-beta superfamily. Binding triggers conformational changes that are shunted down into the cell's interior where a series of biochemical reactions occur, ultimately affecting the cell's behavior. The mutations block this process. This discovery may provide a means of genetic diagnosis and a potential target for the therapy of people with familial (and possibly also sporadic) primary pulmonary hypertension.

How common is pulmonary hypertension?

There are no clear statistical data on the prevalence of this condition. This may be due to the fact that many other diseases may cause or contribute to pulmonary hypertension. Often, these other conditions may be more readily diagnosed and treated without detecting pulmonary hypertension. Therefore, the data on prevalence of pulmonary hypertension may be obscured.

What are the signs and symptoms of pulmonary hypertension?

Many people with pulmonary hypertension may have no symptoms at all, especially if the disease is mild or in early stages.

Pulmonary hypertension symptoms may include:

  • The most common symptoms of pulmonary hypertension is shortness of breath that worsens with activity.
  • Other common complaints are cough, fatigue, dizziness, and lethargy.
  • With the advancement of the condition and ensuing right heart failure, shortness of breath may get worse and retention of fluid in the body may increase (due to failure of the heart to pump blood forward) resulting in swelling the legs.
  • People may also complain of chest pain and angina.

Signs of pulmonary hypertension may include:

  • A rapid breathing, hypoxia (low oxygen level in the blood), and swelling in the legs.
  • In severe pulmonary hypertension, the doctor may hear louder than normal components of heart sounds when he or she listens to the heart with a stethoscope (auscultation).
  • The doctor may also feel elevation of the chest wall when the heart pumps and this may indicate enlargement of the right side of the heart suggestive of pulmonary hypertension (right ventricular heave).

How is pulmonary hypertension diagnosed?

The first step in diagnosis of pulmonary hypertension is to clinically suspect it. This may be done as part of an evaluation of another disease that can lead to pulmonary hypertension (such as scleroderma or chronic obstructive pulmonary disease) or based on patients and signs and symptoms as described above.

Many tests, such as echocardiogram, may be performed that be give us clues to the possibility of pulmonary hypertension. But the gold standard (the best test available) is right heart catheterization. This test entails inserting a catheter through the groin into the femoral vein, a large vein in the lower body (or under the collar bone or in the upper arm into the subclavian vein, a large vein in the upper body) and advancing it to the right side of the heart. The catheter is connected to a device that can monitor and measure blood pressure in the right side of the heart and pulmonary arteries.

During right heart catheterization, response to certain medication to treat pulmonary hypertension can be assessed. This is done by administering medications for pulmonary hypertension while the patients still has the catheter placed in heart. Then pulmonary blood pressure is monitored and the response to treatment is compared to no treatment. This can give the physicians a clue as to if an individual is a candidate for a certain therapy and also what dosage of the medicine may be appropriate.

Pulmonary hypertension is defined as the mean pulmonary artery blood pressure greater than 25 millimeter of mercury (mmHg) measured by right heart catheterization. The pressures can be much higher than 25 mmHg in some people. Therefore, the pulmonary hypertension can be labeled as mild, moderate, or severe based on the pressures. Mean arterial pressure is two-thirds of the difference between systolic and diastolic blood pressure (systolic is the upper number and diastolic is the lower number in measuring blood pressure). As explained above, the pulmonary blood pressure is much lower than the systemic blood pressure.

What tests other than right heart catheterization may be used in diagnosing pulmonary hypertension?

Other tests available for diagnosing pulmonary hypertension include electrocardiogram (ECG), chest x-ray, and echocardiogram. An ECG may show some abnormalities that may be suggestive of right heart failure. Chest x-ray may also show enlargement of the chambers of the right heart. And echocardiogram (ultrasound of the heart) shows ultrasound images of the heart and can detect evidence of right heart failure and pressures in the pulmonary artery can be estimated. These tests, in the right clinical setting, are very useful in diagnosing pulmonary hypertension.

Other tests may be useful in evaluating the conditions leading to secondary pulmonary hypertension. For example, a ventilation-perfusion scan (V/Q scan) can detect blood clots in the pulmonary arteries suggesting chronic thromboembolic pulmonary hypertension. A pulmonary function test can be useful in diagnosing chronic obstructive pulmonary disease (COPD).

What is the treatment for pulmonary hypertension?

The treatment for pulmonary hypertension depends on the underlying cause.

If left sided heart failure is the primary problem, then adequate treatment of the left heart failure by a cardiologist is the main stray of treatment.

In cases where hypoxia (low oxygen levels) due to any chronic lung disease, such as COPD, is the cause, then providing oxygen and appropriately treating the underlying lung disease by a lung doctor (pulmonologist) is the first step in treatment.

In conditions, such as scleroderma, which often can cause pulmonary hypertension, a rheumatologist is involved in the treatment program.

Anticoagulation (thinning the blood) may be a treatment option if the main underlying cause is thought to be recurrent blood clot (chronic thromboembolic pulmonary hypertension). As indicated in previous section, referral to a specialty center may be warranted for a possible surgical removal of blood clot (thromboendarterectomy).

For patients with primary pulmonary hypertension (those with no underlying cause), more advanced therapy may be attempted. These drugs have complex mechanisms, but in general they work by dilating (opening up) the pulmonary arteries and, therefore, by reducing the pressure in these blood vessels.

Some of the most commonly used drugs prescribed to treat pulmonary hypertension include:

These more advanced therapies can also be used for secondary pulmonary hypertension that may be too severe and not adequately controlled by the usual treatment of the underlying condition.

It is worth mentioning that regardless of the cause of pulmonary hypertension, supplemental oxygen and diuretics (water pills) may play an important role in relieving the symptoms of pulmonary hypertension of any cause. Therefore, they may be prescribed by the physician treating pulmonary hypertension.

Low oxygen in the atmosphere causes low blood oxygen levels and aggravates pulmonary hypertension. Therefore, patients with pulmonary hypertension may benefit from breathing supplemental oxygen, especially during air travel or traveling to high altitude destinations.

Despite advances in various treatments, there is no cure for pulmonary hypertension.

What is the prognosis for pulmonary hypertension?

Generally, the prognosis of pulmonary varies depending on the underlying condition that is causing it. For primary pulmonary hypertension, the overall prognosis depends on the severity and whether treatment was instituted. The statistics show a survival of about 3 years in primary pulmonary hypertension without any therapy. Some of the other factors may indicate even poorer prognosis which include severe symptoms, age of onset greater than 45 years, evidence of right sided heart failure, and failure to respond to treatment. For patients with primary pulmonary hypertension who get started on treatment and respond to it, the prognosis is better. Studies are underway to determine optimal treatment regimens.

 

 

 

 

 

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