Typically “blood pressure,” “high blood pressure” and “hypertension” refer to the systemic pressure throughout your body. Systemic blood pressure measures the pressure in your brachial artery (found in your arm) while the left side of the heart pumps oxygen-rich blood from the lungs into the rest of your body. It’s measured with a traditional arm cuff.
Pulmonary hypertension (or PHT) is high blood pressure that occurs in the arteries in the lungs. It is a different measurement altogether from systemic blood pressure.
It reflects the pressure the heart must exert to pump blood from the heart through the arteries of the lungs.
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 pulmonary veins carry the blood with oxygen back to the left side of the heart for distribution to the rest of the body via the systemic circulation.
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).
Systemic and pulmonary circulation: two separate flow patterns
The blood pressure measured on your arm isn’t directly measuring anything related to the blood flow between your heart and lungs. That’s a separate “loop” in the circulatory system. Pulmonary blood pressure focuses on the pressure of blood flow in your lungs.
The right side of the heart receives the oxygen-emptied blood as it returns from the body and pumps this blood from the right side of the heart into the blood vessels of the lungs, where the blood gathers oxygen again.
From there, it leaves the lungs and enters the left side of the heart to carry the oxygen-rich blood to the body again.
The numbers in pulmonary hypertension
Pulmonary blood pressure is normally a lot lower than systemic blood pressure. Normal pulmonary-artery pressure is about 14 mm Hg at rest.
If the pressure in the pulmonary artery is greater than 25 mm Hg at rest and 30 mm Hg during exercise, it is abnormally high and is called pulmonary hypertension.
The problem of pulmonary hypertension
The blood vessels that supply the lungs can also constrict and their walls may thicken, so they can’t carry as much blood. As with a kinked garden hose, pressure builds up and backs up.
The heart works harder, trying to force the blood through. If the pressure is high enough, eventually the heart can’t keep up, and less blood can circulate through the lungs to pick up oxygen.
What causes pulmonary hypertension?
There are many causes of pulmonary hypertension. Often more than one mechanism is involved in a specific disease process. This can also change as the disease progresses.
Diseases that effect flow out of the heart to the rest of the body result in backflow of blood (stacking of blood) that raises pulmonary venous pressures leading to pulmonary hypertension.
Hypoxic pulmonary vasoconstriction is the process in which the lung vessels narrow in attempt to divert blood from poorly functioning segments of the lung.
For instance, when pneumonia develops, a portion of lung becomes inflamed and works poorly in performing the functions of the lung (to add oxygen and remove carbon dioxide from the blood).
This process diverts blood from these poorly working areas and sends it to better functioning lung tissue. However, a problem develops when all the blood has a low oxygen level (hypoxia). This causes constriction of the vessels on the pulmonary arterial side and hence raises the pressure.
Remodeling of blood vessels also occurs in some diseases whereby the inner lining (lumen) of the vessel becomes narrowed due to inappropriate growth of the tissue within and around the vessel. Masses and scarring from other diseases can compress and narrow vessels causing increased resistance to flow resulting in elevation of pressures.
In a fairly common parasitic infection in the Middle East (schistosomiasis), the blood vessels in the lung become blocked by the parasites causing pulmonary artery hypertension.
Some substances cause constriction of the blood vessels. Pulmonary hypertension 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.
Some diseases raise pulmonary pressures to cause pulmonary artery hypertension for unclear reasons. Perhaps an unknown toxin or chemical effects the blood vessels by causes constriction or inappropriate growth of the tissue within or around the vessel.
For example, there is a condition known as portopulmonary hypertension that is result of liver failure.
When these individuals receive a liver transplant, the pulmonary hypertension disappears suggesting that the failing liver is unable to clear some biochemical that leads to pulmonary artery hypertension.
Patients with PHT may experience:
- Shortness of breath
Symptoms and diagnosis of primary pulmonary hypertension (PPH) can be tricky.
Early on, you may think you’re simply “out of shape” because general fatigue and tiredness are often the first symptoms. It is more noticeable if you experience breathing difficulty, dizziness or even fainting spells that some patients report.
As the condition progresses, you may begin to notice swelling in the ankles or legs, bluish discoloration of the lips and skin, and chest pains.
These later symptoms indicate your body is not circulating enough oxygen-filled blood from your lungs which is a definite health problem that needs treatment.
Although primary pulmonary hypertension (PPH) is rare, diagnosing and treating PPH is often delayed and can be very complex. Because these symptoms increase gradually, patients may not recognize them.
Furthermore, most people do not seek medical help if they mistakenly believe they are simply “out of shape.”
With PPH, some patients will have many symptoms while other patients may only have a few clues to the problem. The medical evaluation requires an in-depth understanding of lung and circulation problems because these same symptoms can also signal other types of health problems.
For these reasons, patients with symptoms that suggest pulmonary hypertension should be evaluated at a medical center with expertise and experience in pulmonary hypertension.
Primary pulmonary hypertension
When not accompanied by underlying heart and lung disease or other illnesses, it is called primary pulmonary hypertension.
The greatest number of cases is reported in women between ages 21 and 40. Several cases of primary pulmonary hypertension have been linked to the use of the appetite suppressants fenfluramine and dexfenfluramine.
Secondary pulmonary hypertension
If a pre-existing disease triggered the PHT, doctors call it secondary PHT. That’s because it’s secondary to another problem, such as a heart or lung disorder like:
- Congenital heart defects
- It’s important to repair congenital heart problems (when possible) before permanent pulmonary hypertensive changes develop.
- Intracardiac left-to-right shunts
- A ventricular or atrial septal defect or a hole in the wall between the two ventricles or atria can cause too much blood flow through the lungs. This situation is sometimes called Eisenmenger complex.
- Heart valve conditions
- These include mitral stenosis, a narrowing of the mitral valve. Fixing the valve usually reverses the PHT.
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How is pulmonary hypertension treated?
Once PHT has been diagnosed, medical therapy is often needed. Regularly follow up with a cardiologist or pulmonologist trained in caring for patients with PHT.
For those diagnosed with secondary PHT
As long as the underlying disease exists, it will keep causing PHT. So, for example, if you have a congenital heart defect causing your pulmonary hypertension, your PHT will not go away unless your congenital defect can be fixed.
However, once you have PHT, even if the initial defect is cured, it may not make the pulmonary hypertension go away, especially if you have had PHT for quite some time.
PHT is a serious illness and it will usually require separate treatment, which may include oxygen, agents to help your heart pump better, diuretics, anticoagulants (blood thinners) and medications to lower PHT. Sometimes lung transplants also are performed.
If you’ve begun medical treatment for PHT, follow your medical treatment plan very strictly. Never assume you can alter the dose or frequency of any of your medicines without your physician’s approval.
Not following your healthcare team’s instructions can be extremely dangerous. Medical therapy has significantly improved the outlook for most PHT patients, but it doesn’t “cure” PHT.
Special precautions for those with PHT
You can have a diagnosis of PHT and live an active, fulfilling life. Still, you should consider certain measures and precautions. PHT is a lifelong illness that can be made worse by a variety of factors, such as:
- Going to high altitude
- Avoid conditions where the ambient oxygen concentration may be decreased, such as high altitude and travel in airplane cabins that are not pressurized. Supplemental oxygen is often recommended during air travel.
- Engaging in exercise and physically demanding activities
- Seek your healthcare professional’s advice about physical activity. If you have PHT, you should be as active as physically possible.
Physical activity can be associated with marked increases in pulmonary artery pressure. Thus, don’t do activities that produce dangerous symptoms, such as chest pain or dizziness.
A supervised cardiopulmonary rehabilitation program may help promote appropriate physical conditioning. Before starting an exercise program, ask your physician what activities are safe and healthy for you.
Many patients with PHT report having “good and bad days.” If you need to rest, do so.
- Taking medications
Most medications for colds, flus and other medical conditions are safe for people with PHT. Still, caution should be taken both in prescription medications and over-the-counter drugs.
Any anesthetics or sedatives can be very hazardous. Ask your physician which medications are safe.
- Pregnancy and childbirth
Pregnancy and delivery produce dramatic changes that can seriously endanger your life. Thus, avoid pregnancy by practicing a safe and effective method of contraception.
Avoid oral contraceptives as they can aggravate PHT. The most effective form of contraception for people with significant PHT is surgical sterilization.
Contracting respiratory tract infections, pneumonia and the flu
- Antibiotic therapy is recommended for significant respiratory tract infections. Those with PHT should also consider getting a pneumococcal pneumonia vaccine and yearly flu vaccines since these illnesses can be very serious with PHT patients.