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The left and right pulmonary arteries are blood vessels through which the heart supplies blood to the lungs. Blood pressure refers to the force with which blood presses against the walls of blood vessels, and pulmonary artery pressure, or PA pressure, is a term that describes the blood pressure inside the pulmonary arteries. Normally, blood passes without much effort from the lower right chamber of the heart into the pulmonary arteries and the lungs, and the pressure inside each pulmonary artery is low. In the condition known as pulmonary hypertension, the pulmonary artery pressure is abnormally high, resulting in symptoms such as breathlessness, tiredness and a rapid heartbeat.
A number of factors can raise this pressure, including narrowing of the arteries and stiffening of the arterial walls. Certain disorders such as COPD, or chronic obstructive pulmonary disease, are associated with low blood oxygen levels, and the reduced oxygen causes thickening and narrowing of pulmonary artery walls. In the condition known as pulmonary embolism, blood clots in the arteries may develop, causing a sudden increase in pressure. Pulmonary artery hypertension is also known to be associated with sickle cell disease, a disorder in which red blood cells are abnormal.
If the left side of the heart fails, possibly due to a heart attack or faulty heart valve, back pressure builds up in the pulmonary veins which drain blood from the lungs into the heart, and extends to involve all the pulmonary blood vessels, giving rise to increased pressure in the pulmonary artery. Pulmonary artery hypertension forces the heart to work harder to move blood into the lungs, and the right lower chamber of the heart may become weakened and enlarged. This type of heart failure is known as cor pulmonale.
Pulmonary artery pressure may be investigated directly by inserting a tube into a vein in the leg or arm, and moving it along until it reaches the right side of the heart. From there, it can be used to measure the pressures in both the pulmonary artery and the heart's lower right chamber. Chest X-rays can be taken to examine the lungs, and ECGs, or echocardiograms, may be used to check the cardiovascular system to establish a possible cause of increased pulmonary artery pressure.
The treatment of raised pressure in the pulmonary artery depends on the cause, but the condition itself has no cure. Management of any underlying disease is carried out to reduce symptoms. In the case of some conditions, or where no cause has been found, drugs which dilate blood vessels may be effective in helping to lower pulmonary artery pressure.