Primary vs. Secondary

Pulmonary hypertension, also known as pulmonary arterial hypertension, is divided into two main categories: primary pulmonary hypertension that is not caused by any other disease or condition; and secondary pulmonary hypertension that is caused by another underlying condition. The more common of the two is secondary pulmonary hypertension.

Hypertension is a disorder characterized by consistently high blood pressure. Generally, high blood pressure consists of systolic blood pressure (the "top" number, which represents the pressure generated when the heart beats) higher than 140, or diastolic blood pressure (the "bottom" number, which represents the pressure in the vessels when the heart is at rest) over 90.

A Class In Its Own

There is a newer classification of pulmonary hypertension, which is based on the main underlying cause of the condition. This classification is based on whether it is due to one or more of the following:

• left sided heart disease


• lung disease


• blood clots


• constriction of arteries due to any reasons (including primary pulmonary hypertension), and


• obstruction from outside of blood vessel (for example from diseases of the chest wall compressing the blood vessels)

What's The Cause?

Pulmonary hypertension can be caused by diseases of the heart and the lungs in the following examples:

• chronic obstructive pulmonary disease (COPD)


• emphysema


• failure of the left heart ventricle


• recurrent pulmonary embolism (blood clots traveling from the legs or pelvic veins obstructing the pulmonary arteries or chronic thromboembolic pulmonary hypertension), or


• underlying diseases such as scleroderma

Other conditions that may cause pulmonary hypertension include:

• dermatomyositis


• systemic lupus erythematosus


• sarcoidosis


• human immunodeficiency virus (HIV), and


• advanced liver disease (porto-pulmonary hypertension)

The condition of pulmonary hypertension can also be caused by chronic low blood oxygen levels as in sleep apnea or other chronic lung disease. As previously stated, pulmonary hypertension is caused by other illnesses and thus can also be referred to as secondary pulmonary hypertension. Primary pulmonary hypertension is when the condition occurs without underlying heart and lung disease or other illnesses. Primary pulmonary hypertension is more common in females than in males, and in younger people.Some street drugs, such as methamphetamines or cocaine, can cause severe pulmonary hypertension. Recently, pulmonary hypertension has been reported, on rare occasion, with the use of anti-obesity drugs such as dexfenfluramine (Redux) and Fen/Phen. These drugs have since been removed from the market.