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 at rest. 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 to the lungs.
Types of Pulmonary Hypertension
Pulmonary hypertension may occur without an identifiable underlying cause (idiopathic pulmonary arterial hypertension (IPAH) or unexplained pulmonary arterial hypertension). Pulmonary arterial hypertension could be associated with a variety of conditions, including cirrhosis, AIDS, connective tissue diseases, weight reducing drugs and certain toxins (APAH).
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).
Idiopathic pulmonary arterial hypertension (IPAH) is a rare condition, with an estimated incidence of approximately six in every million patients per year, although it appears to be becoming more frequently detected by simple noninvasive means, such as echocardiographic examination. The illness most often occurs in young adults and is more common in women.
Symptoms of IPAH
The most common symptoms 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. IPAH is rarely picked up in 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 hypertension and cannot find other reasons for the hypertension. The evaluation of patients with pulmonary hypertension in order to determine optimal treatment is a meticulous process. It requires a series of tests and direct measurement of the pressures in the heart and lungs before the correct treatment can be selected.
Treatment of IPAH
The course of IPAH is often one of steady deterioration and reduced life expectancy. The untreated patients have a probability of survival of 68% at one year, 48% at three years, and 34% at five years. Patients with APAH are treated the same way as patients with IPAH.
Treatment of IPAH varies according to the stage of the disease and systematic evaluation is required to decide which therapy is best for an individual patient.
- Calcium channel blockers: At present, approximately 10% of patients can be treated with calcium channel blocking drugs given by mouth. By relaxing the smooth muscle in the blood vessels, these calcium channel blockers improve the ability of the heart to pump blood.
- Endothelin receptor blockers: Enothelin is normally produced in the body and causes the vessels to tighten. It is increased in patients with IPAH. Bosentan (Tracleer) and Ambrisentan (Letairis) are endothelin receptor blockers. They block the action of endothelin. These are tablets taken by mouth.
- Sildenafil (Revatio) and Tadalafil (Adcirca): Nitric Oxide is naturally produced in the vessels and is important to maintain health. It is reduced in patients with IPAH. Sildenafil and Tadalafil increase the availability of nitric oxide in the vessel, which causes it to dilate. These are tablets taken by mouth.
- Epoprostenol (Flolan): Prostacyclin is normally produced in cells of the body and dilates the blood vessels. Epoprostenol is a synthetic equivalent of the naturally produced prostacyclin, which can be given as a continuous intravenous infusion by a battery powered pump. This requires placement of a catheter in one of the big veins.
- Treprostinil (Remodulin): Treprostinil is also a synthetic prostacyclin and is given by continuous subcutaneous (in the skin) infusion using a small battery operated pump. This drug is administered via an intravenous line. Inhaled Trepostinil (Tyvaso) can also be administered by a special nebulizer.
- Iloprost (Ventavis), another synthetic prostacyclin, is given by inhalation via a specialized nebulizer. It needs to be taken at least six times a day.
The benefits of other therapies such as:
- combining these agents
- newer agents
are currently being evaluated. Heart-lung transplantation or lung transplantation
alone are options for the severely affected patient.
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Last Reviewed: Sep 27, 2010
Namita Sood, MD, FCCP
Associate Professor of Pulmonary, Critical Care & Sleep
College of Medicine
The Ohio State University