Pulmonary Hypertension (cont.)

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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.
Medically Reviewed by a Doctor on 11/25/2013

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