Every time blood passes through the heart, the lower right chamber, that is the right ventricle, pumps blood to the lungs via a blood vessel known as the pulmonary artery. Inside the lungs, the blood releases carbon dioxide and absorbs oxygen. Normally, blood flows easily through the vessels in the lungs and hence, blood pressure remains low. An alarming blood pressure rise in the lungs causes pulmonary arterial hypertension. There are several reasons for yielding the disease. In some cases, the problem can be caused by a combination of attributing factors. Treatment in such cases becomes quite complex. In case the cause is unknown, the condition is known as idiopathic pulmonary hypertension.

Some of the most important causes of pulmonary arterial hypertension are:

• Drug abuse: The problem of pulmonary arterial hypertension can also be triggered by drug abuse. Though a number of illegal drugs can cause the issue, most notable offenders are cocaine and methamphetamine.
• Congestive heart failure: In addition to other medical conditions, several cases of congestive heart failure causes pulmonary arterial hypertension.
• Blood clotting in the lungs: Another important cause of pulmonary arterial hypertension is blood clotting inside the lungs. In several medical conditions, blood starts to clot inside the lungs, resulting in a number of lung-related conditions, including pulmonary arterial hypertension.