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Low Blood Pressure > Pulmonary Hypertension
Low Blood Pressure
(Pulmonary Hypertension)
 

Description
Millions of people are affected by high blood pressure (hypertension), a condition in which blood travels through the body's arteries at a pressure too high. A far less common type of high blood pressure affects only the arteries in the lungs. Known as pulmonary hypertension, it's a serious illness that becomes progressively worse. For some people, pulmonary hypertension eventually proves fatal.
Pulmonary hypertension begins when tiny arteries in your lungs become narrow or blocked. This causes increased resistance to the flow of blood in the lungs, which in turn raises pressure within the pulmonary arteries. As the pressure builds, your heart's lower right chamber (right ventricle) must work harder to pump blood through your lungs, eventually causing the heart muscle to weaken and sometimes to fail completely.
Although pulmonary hypertension isn't curable, treatments are available that can help lessen symptoms and improve quality of life for many people with pulmonary hypertension.

Signs and Symptoms (Warning Sign)
The signs and symptoms of pulmonary hypertension are subtle in the early stages of the disease and may not appear for months or even years. As the disease progresses, signs and symptoms become more noticeable. They include:

  • Shortness of breath (dyspnea). Initially, you may notice that you're short of breath only when you exert yourself physically, but eventually you may be short of breath most of the time, even when you're at rest.
  • Fatigue.
  • Dizziness or fainting spells (syncope).
  • Chest pressure or pain.
  • Swelling (edema) in your ankles, legs and eventually in your abdomen (ascites).
  • Bluish color to your lips and skin (cyanosis).
  • Racing pulse or heart palpitations

Cause
Your heart has two upper and two lower chambers. Each time blood passes through your heart, the lower right chamber (right ventricle) pumps blood to your lungs through a large blood vessel (pulmonary artery). In your lungs, the blood releases carbon dioxide and picks up oxygen. The oxygen-rich blood then flows through the pulmonary veins to the left side of your heart. From there, it's pumped by the left ventricle to the rest of your body through another large blood vessel, the aorta.

Ordinarily, the blood vessels in your lungs provide less resistance to blood flow than the blood vessels in the rest of your body do. For that reason, blood pressure is usually much lower in the vessels in your lungs. Normal systolic pressure in your lungs is about 14 millimeters of mercury (mm Hg) when you're at rest. Pulmonary hypertension is defined as systolic lung blood pressure greater than 25 mm Hg at rest and 30 mm Hg during exercise.

The overall rise in blood pressure in pulmonary hypertension is the end result of a process that begins with changes in the endothelial cells that line the lungs' arteries. These changes cause the formation of extra tissue that eventually narrows or completely blocks the blood vessels. Scarring (fibrosis) usually also occurs, making the arteries stiff as well as narrow. This creates increased resistance to blood flow, which raises pressure in the pulmonary arteries.

Primary pulmonary hypertension
When an underlying cause for high blood pressure in the lungs can't be found, the condition is called primary pulmonary hypertension (PPH). But although the exact cause of PPH isn't known, scientists believe that most people who develop the disorder are especially sensitive to substances that cause the blood vessels to constrict.

Other people with PPH have an inherited predisposition for the disease. In these people, pulmonary hypertension is triggered by another medical condition such as chronic liver disease (cirrhosis), AIDS, sickle cell anemia, scleroderma and lupus.

Secondary hypertension
Pulmonary hypertension resulting directly from another medical problem is called secondary pulmonary hypertension. Medical conditions that may lead to secondary pulmonary hypertension include:

  • Blood clots in the lungs (pulmonary emboli).
  • Chronic obstructive pulmonary diseases, such as emphysema.
  • Connective tissue disorders, such as scleroderma.
  • Sleep apnea.
  • Congenital heart disease.
  • Lung diseases such as pulmonary fibrosis — a condition that causes scarring in the tissue between the lungs' air sacs (interstitium). In this case, pulmonary hypertension may occur when the lungs' smallest arteries and capillaries are compressed and obliterated by scar tissue.
  • Left-sided heart failure. When your heart's left ventricle weakens and can't pump out enough blood, the increase in pressure backs up through the pulmonary veins to the arteries in your lungs.
  • High altitude. People living above an altitude of 8,000 feet may develop pulmonary hypertension as a result of low blood oxygen (hypoxemia), which constricts the small pulmonary arteries. Especially at risk are people who climb to high elevations without first becoming acclimated. Climbers unaccustomed to high altitudes are also at risk of pulmonary edema, a condition in which the air sacs in the lungs fill with fluid instead of with air and which is always associated with pulmonary hypertension.


Risk factors
Although anyone can develop either type of pulmonary hypertension, older adults are more likely to have secondary pulmonary hypertension and young people are more likely to have primary pulmonary hypertension. Primary pulmonary hypertension is also more common in women than it is in men. .


Diagnosis
In some cases, your doctor may suspect you have pulmonary hypertension based on the results of a chest X-ray or electrocardiogram (ECG) — a noninvasive test that measures electrical impulses traveling through your heart. But most often, pulmonary hypertension isn't detected in the early stages.

One reason is that one of the first symptoms — shortness of breath — isn't always taken seriously in otherwise healthy young people and is often diagnosed as mild asthma or even dismissed as a nervous reaction. Because shortness of breath is subtle and slow in onset, pulmonary hypertension may not be accurately diagnosed for years. On the other hand, if you're constantly short of breath, rather than only occasionally as is usually the case with asthma, your doctor is more likely to look for pulmonary hypertension.

Even when the disease is more advanced, its signs and symptoms often mimic those of other heart and lung conditions. For this reason, and because no one test can diagnose pulmonary hypertension, your doctor is likely to recommend one or more tests to rule out other possible reasons for your problem. These tests include:

  • Echocardiography (ultrasonic cardiography). This noninvasive test uses harmless sound waves that allow your doctor to see your heart without making an incision. During the procedure, a small, plastic instrument called a transducer is placed on your chest. It collects reflected sound waves (echoes) from your heart and transmits them to a machine that uses the sound wave patterns to compose images of your beating heart on a monitor. These images show how well your heart is functioning, and recorded pictures allow your doctor to measure the size and thickness of your heart muscle. Sometimes your doctor will recommend an exercise echocardiogram to help determine how well your heart works under stress. In that case, you'll have an echocardiogram before exercising on a treadmill and another test immediately afterward. Traditional echocardiograms are safe and generally painless. An exercise echocardiogram carries a slight risk of a heart attack brought on by exercise, so doctors recommend this test only when they feel it's needed.
  • Pulmonary function tests. These noninvasive tests measure how much air your lungs can hold and the airflow in and out of your lungs. They can also measure the amount of gases exchanged across the membrane between your lung wall and capillary membrane. An abnormality here may be the first indication of PPH. During the tests, you'll most likely be asked to blow into a simple instrument called a spirometer.
  • Perfusion lung scan. This test uses small amounts of radioactive tracers (radioisotopes) to study blood flow (perfusion) in your lungs. The radioisotopes are attached to substances known as radiopharmaceuticals, which are injected into a vein in your arm. Immediately afterward, a special camera (gamma camera) takes pictures of blood flow in your lungs' blood vessels. A lung scan is generally used to determine whether blood clots may be causing symptoms of pulmonary hypertension. It's usually performed in conjunction with another test known as a ventilation scan. In this test, you inhale a small amount of radiopharmaceutical while a gamma camera records the movement of air into your lungs. The two-test combination is known as a ventilation-perfusion (V/Q) scan, and in its entirety usually takes less than an hour. Only small amounts of radioactivity are used, and a V/Q scan seldom causes any side effects or complications.
  • Right heart catheterization. Performed on an outpatient basis using local anesthesia, this test is often the most reliable way of diagnosing pulmonary hypertension. During the procedure, a cardiologist places a thin, flexible tube (catheter) into a vein in your neck or groin. The catheter is then threaded into your right ventricle and pulmonary artery. Right heart catheterization allows your doctor to directly measure the pressure in the main pulmonary arteries and right ventricle. It's also used to evaluate the effect different drugs may have on your heart in order to find the most effective treatment.  Risks of the procedure include trauma to the vein in which the catheter is inserted, the formation of blood clots at the tip of the catheter, and heart attack or stroke.
  • Fast computerized tomography (CT). A CT scan allows your doctor to see your organs in two-dimensional "slices." Split-second computer processing creates these images as a series of very thin X-ray beams pass through your body. A contrast medium is commonly used to help visualize the area. Some hospitals now use what's known as a fast CT machine. It can scan your arteries in less than 20 seconds as opposed to 20 minutes or more for a standard CT. Speed is important because it allows the dye to be visualized while still in your arteries.
  • Magnetic resonance imaging (MRI). This test uses no X-rays. Instead, a computer creates tissue "slices" from data generated by a powerful magnetic field and radio waves. Although not yet routinely used to diagnose pulmonary hypertension, it's showing great value in assessing the pulmonary arteries. It can't, however, measure artery pressure — a procedure that's necessary if you're taking medications to control PPH.

 

 
 
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