What is pulmonary hypertension?
The right ventricle pumps blood returning from the body into the pulmonary arteries to the lungs to receive oxygen. The pressures in the lung arteries (pulmonary arteries) are normally significantly lower than the pressures in the systemic circulation. When pressure in the pulmonary circulation becomes abnormally elevated, it is referred to as pulmonary hypertension, pulmonary artery hypertension, or PAH.

Pulmonary hypertension generally results from constriction, or stiffening, of the pulmonary arteries that supply blood to the lungs. Consequently, it becomes more difficult for the heart to pump blood forward through the lungs. This stress on the heart leads to enlargement of the right heart and eventually fluid can build up in the liver and other tissues, such as the in the legs.

What are primary and secondary pulmonary hypertension?
In the conventional classification, pulmonary hypertension, which is also called pulmonary arterial hypertension, is divided into two main categories; 1) primary pulmonary hypertension (not caused by any other disease or condition); and 2) secondary pulmonary hypertension (caused by another underlying condition). Secondary pulmonary hypertension is much more common than primary pulmonary hypertension.

A newer classification of this condition is based on the main underlying cause of pulmonary hypertension. This system classifies the condition based on whether it is due to:

• 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 is the treatment for pulmonary hypertension?
The treatment for pulmonary hypertension depends on the underlying cause.

If left sided heart failure is the primary problem, then adequate treatment of the left heart failure by a cardiologist is the main stray of treatment.

In cases where hypoxia (low oxygen levels) due to any chronic lung disease, such as COPD, is the cause, then providing oxygen and appropriately treating the underlying lung disease by a lung doctor (pulmonologist) is the first step in treatment.

In conditions, such as scleroderma, which often can cause pulmonary hypertension, a rheumatologist is involved in the treatment program.

Anticoagulation (thinning the blood) may be a treatment option if the main underlying cause is thought to be recurrent blood clot (chronic thromboembolic pulmonary hypertension). As indicated in previous section, referral to a specialty center may be warranted for a possible surgical removal of blood clot (thromboendarterectomy).

For patients with primary pulmonary hypertension (those with no underlying cause), more advanced therapy may be attempted. These drugs have complex mechanisms, but in general they work by dilating (opening up) the pulmonary arteries and, therefore, by reducing the pressure in these blood vessels.

Some of the most commonly used drugs prescribed to treat pulmonary hypertension include:

• epoprostenol (Flolan),
• bosentan (Tracleer),
• intravenous treprostinil (Remodulin),
• inhaled iloprost (Ventavis),
• sildenafil (Viagra, Revatio),
• calcium channel blockers (such as nifedipine),
• sitaxsentan (Thelin) - not FDA approved in the U.S., and
• ambrisentan (Letairis).

These more advanced therapies can also be used for secondary pulmonary hypertension that may be too severe and not adequately controlled by the usual treatment of the underlying condition.