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Primary Pulmonary Hypertension is a serious lung and heart disorder stemming from the blood vessels in the lungs. These blood vessels constrict causing the pressure in the pulmonary artery (that connects the heart to the lungs) to rise and create a life threatening situation.

If the disease can be attributed to a specific cause, it is sometimes called Secondary Pulmonary Hypertension (SPH) or simply Pulmonary Hypertension (PH). If the disease cannot be linked to a specific cause it is usually called Primary Pulmonary Hypertension (PPH). Ironically, the disease is usually classified as PPH when connected to diet drug use, although the cause has been clearly linked to the drug use. The reason for this may that the mechanics of the link are not well understood by doctors.

What Happens

In a person with PPH, the blood pressure of the blood vessels in their lungs (pulmonary arteries) rises to abnormally high levels, this is called hypertension. Thus the disease, simply understood is high blood pressure inside of the lungs.

Normally, the pulmonary arteries bring blood with a low oxygen content from the heart's right ventricle. The right side of the heart then pumps the oxygen depleted blood into the lungs. Once inside the lungs, this blood is given the oxygen the body needs. The blood then travels to the left side of the heart, which pumps it throughout the body via the aorta.

In a person with PPH, the tiny blood vessels in the lungs begin to change and close off. (see below) This closure prevents the blood from flowing freely and the pulmonary artery pressure in people affected more than doubles.
The average person's pulmonary-artery pressure is about 14 mmHg when they are resting. When a person develops PPH, the blood pressure in the pulmonary artery is about 25 mmHg when resting and over 30 mmHg when exercising. These pressures will gradually increase as the disease progresses and many patients have pulmonary pressures above 100 mmHg.

The increased resistance from the lung arteries then puts greater and greater stress on the right ventricle. As the resistance worsens, the heart has to work harder and harder in an effort to circulate enough blood through the lungs.

In Detail: What Happens in the Lung Arteries

The lungs contain millions tiny capillary blood vessels. Each lung capillary is only the width of a small hair, through which blood cells must travel. A type of cell called an endothelial cell, lines the inside of these tiny blood vessels, the outside of the blood vessel is covered with smooth muscle cells. Endothelial cells function to prevent blood from escaping and hold the blood vessel together, while the muscle cells control the diameter of the blood vessel, making it wider or narrower to regulate the flow of blood is between the heart and lungs.

For reasons doctors do not yet understand, in a person with PPH, the endothelial cell linings in the lung capillaries get pulled off the vessel walls. With these cells designed to prevent blood leakage gone, blood leaks and enters the smooth muscle cells. The muscle cells then become continuously constricted as a consequence.
As this happens to thousands of cells in capillaries throughout the lungs, the flow of blood between the heart and lungs becomes increasingly difficult resulting in the symptoms of PPH and eventual heart failure.


The symptoms of PPH include shortness of breath also called dyspnea. This shortness of breath can come about after little or no physical exertion. Other symptoms include: fatigue, chest pain and anginal chest pain, dizziness and fainting spells. PPH is a rare disorder, occurring in about two persons per million population per year.

See more on symptoms and diagnosis >>

Causes of PPH

In most cases doctors do not know what causes PPH, or they may say it is of unknown etiology. Increasingly however, doctors are discovering causes that previously were not considered. Today doctors have listed certain Drugs as having a "Definite causal relationship" to PPH. These include: Aminorex, Fenfluramine, Dexfenfluramine and Toxic rapeseed oil. It is now widely believed that the millions of users of diet drugs, what doctors call Anorectic agents or appetite suppressants have spawned thousands of new PPH cases.

Secondary pulmonary hypertension (SPH) is usually a complication of several conditions that can affect the heart and lungs. Common causes of SPH include lung disorders such as emphysema and bronchitis. Vascular diseases such as scleroderma or lupus are also causes. Congenital heart diseases and blood clots in the pulmonary artery, HIV infection and liver diseases can lead to SPH.


PPH is a deadly disease and the average survival after the diagnosis is usually less than 3 years. However, with early diagnosis and new treatments, patients may survive for more than 10 years. According to the PPH Association, recent data suggests that the length of survival is continuing to improve, and some patients may be able to manage the disorder for 15 to 20 years or longer.

The prognosis for people diagnosed with secondary pulmonary hypertension is dependent on the disease which causes the pulmonary hypertension. However, these survival rates may be poorer than those with PPH because of the already weakened state of the patient.

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