What is Pulmonary Hypertension?
Pulmonary hypertension is a lung disorder in which blood pressure in the pulmonary artery rises above normal levels. The pulmonary artery is the blood vessel carrying oxygen-poor blood from the heart to the lungs. Pulmonary hypertension is present when the mean pulmonary artery pressure is greater than 25mmHg. This abnormally high pressure (pulmonary hypertension) is associated with changes in the small blood vessels in the lungs, resulting in an increased resistance to blood flowing through the vessels. This increased resistance, in turn, places a strain on the right side of the heart as it has to work against a higher resistance to pump blood into the lungs.
Types of Pulmonary Hypertension
Pulmonary hypertension can be associated with a variety of conditions (secondary pulmonary hypertension) or it may occur without an identifiable underlying cause (Idiopathic, or unexplained pulmonary arterial hypertension--IPAH). Secondary pulmonary hypertension can result from lung disease, heart disease, low oxygen in the blood (hypoxia) and obstruction of the pulmonary vessels (from clots, foreign body, parasites and certain blood disorders). The term pulmonary arterial hypertension (PAH) refers to the disease arising from the pulmonary arteries themselves, while pulmonary hypertension simply means the pressure is high due to influences of other diseases on the pulmonary arteries. Some conditions may be associated with PAH including cirrhosis, HIV/AIDS, congenital heart disease, connective tissue diseases, sickle cell anemia, and certain toxins such as phenfluramine (found in some diet pills).
Idiopathic Pulmonary Arterial Hypertension (IPAH) is a rare condition, with an estimated incidence of approximately 1 in every million patients per year, although it is becoming more frequently detected by simple noninvasive means, such as echocardiographic examination. There is a familial variant of PAH that is genetically transferred from generation to generation in rare cases.
Symptoms of PAH
The most common symptoms of PAH are tiredness and shortness of breath with exertion. Fainting spells, dizziness, ankle or leg swelling, racing pulse and chest pressure or pain are also typical symptoms, but usually present in more advanced disease. PAH is rarely picked up on a routine medical examination. Even in its later stages, the signs of the disease can be confused with other conditions affecting the heart and lungs. IPAH remains a diagnosis of exclusion. This means that it is diagnosed only after the doctor finds pulmonary arterial hypertension and cannot find other reasons to explain its presence. The evaluation of patients with pulmonary hypertension is involved and should include a right heart catheterization in most patients to directly measure the pressures and confirm the diagnosis.
Treatment of PAH
The course of IPAH is often one of steady deterioration and reduced life expectancy, but the survival has improved with the advent of many modern therapies. Treatment of PAH varies according to the stage of the disease and the degree of impairment in one's exertional capacity. At present, a small portion of patients, about 7%, can be treated with oral calcium channel blockers, which are relatively inexpensive and well-tolerated. By relaxing the smooth muscle in the blood vessels, these calcium channel blockers improve the ability of the heart to pump blood. Prostacyclin in the form of prostaglandin I2, is normally produced in the cells of the body, and dilates the blood vessels. A very similar molecule is manufactured as a drug (epoprostenol and treprostinil), which can be given as a continuous intravenous (which requires placement of a catheter in one of the central veins) or subcutaneous infusion by a battery powered pump. It has been shown to improve survival and exercise tolerance of these patients. These continuous infusion therapies are usually reserved for those with the most severe impairment in exertional capacity.
There are also four oral medications available for PAH (sildenafil, tadalafil, bosentan, and ambrisentan) which can be used in those with more moderate impairments in exertional capacity. These are typically well tolerated. Sildenafil and tadalafil should not be taken along with nitrates such as nitroglycerin. Bosentan requires that monthly liver function tests be checked as there is a very small risk of causing damage to the liver. An inhaled prostacylin, either iloprost or treprostinil, can be used in patients with moderate disease as well. Other therapies such as anticoagulation with warfarin (since small micro-clots form in the pulmonary blood vessels in PAH) and diuretics (to help with excess fluid), are often employed as well.
Heart-lung transplantation or lung transplantation alone is an option for severely affected patients who are not doing well despite aggressive medical therapy.To learn more about transplants at UNC see our Transplantation pages.
The factors involved in the development of PAH and the optimal approach to therapy are under continued investigation. Visit our clinical trials homepage to view current studies.
If you have any questions or are interested to learn more about pulmonary hypertension treatment or research at UNC please contact us: Pulmonary Hypertension Clinic 919-966-6838.
Pulmonary Hypertension Association - A not for profit organization dedicated to advancing care and research for PAH patients. Good information about the disease and where to seek care at PAH centers around the country.