Pulmonary arterial hypertension


Pulmonary arterial hypertension

Description, Causes and Risk Factors:

Abbreviation: PAH

Pulmonary arterial hypertension is a syndrome characterised by a progressive increase in pulmonary vascular resistance leading to right ventricular overload and eventually to right ventricular failure and premature death.

PAH is defined as a sustained elevation of mean pulmonary arterial pressure (MPAP) to more than 25 mmHg at rest or to more than 30 mmHg while exercising, with a normal pulmonary wedge pressure (?15 mmHg). In most cases the earliest symptom is dyspnea on physical exertion. Other symptoms include syncope or near syncope, fatigue and peripheral edema, chest tightness and pain similar to angina may occur, particularly on physical exertion.

PAH is a rare disease, with an estimated prevalence of 30-50 cases per million.

The exact cause behind the development of PAH remains unknown. Risk factors include:

    PAH associated with connective tissue disease: PAH is a well-recognized complication of connective tissue diseases such as systemic sclerosis and SLE and in affected patients may also occur in association with interstitial lung disease. The prevalence of PAH in patients with systemic sclerosis has been reported to be up to 16% and in systemic sclerosis patients, pulmonary complications, such as interstitial lung disease and PAH, are now the leading causes of death. Patients with PAH associated with systemic sclerosis have a particularly poor prognosis compared to those with systemic sclerosis without PAH.

  • PAH associated with congenital heart disease: Congenital heart disease is relatively common, affecting around 1% of the population. Within this population 15% will go on to develop PAH. As determined by the level of pulmonary vascular resistance, the most severe form of PAH is Eisenmenger's syndrome, which is associated with the reversal of an initial left to right shunt causing cyanosis and limited exercise capacity.

  • PAH associated with HIV infection: PAH is a rare (estimated prevalence in patients with HIV: 0.5%) but relatively well-documented complication of HIV infection. With the advent of highly active anti-retroviral therapy (HAART) and markedly improved survival, PAH and other non-infectious manifestations of HIV infection are increasingly responsible for HIV-associated morbidity and poor prognosis. In patients with HIV, the HIV-1 envelope glycoprotein GP120 may stimulate the production of endothelin by macrophages. HIV-associated PAH shows a similar clinical picture to IPAH and seems to be independent of the degree of immunosuppression.

  • PAH associated sickle cell disease: Sickle cell disease (SCD) is a genetic disorder of the hemoglobin which results in a chronic hemolytic anemia. Over time and due to the chronic hemolysis the vasculature becomes damaged and pulmonary hypertension can develop. The prevalence of PAH in sickle cell patients is 20-40%. The two year mortality rate of pulmonary hypertension related to SCD is reported up to 50% and is one of the leading causes of death in SCD.

  • Other (thyroid disorders, glycogen storage disease, Gaucher's disease, hereditary hemorrhagic telangiectasia, hemoglobinopathies, myeloproliferative disorders, splenectomy).

PAH is recognized as a complex, multi-factorial condition involving numerous biochemical pathways and different cell types. Endothelial dysfunction is believed to occur early on in disease pathogenesis, leading to endothelial and smooth muscle cell proliferation and structural changes or `re-modeling' of the pulmonary vascular bed resulting in an increase in pulmonary vascular resistance. Endothelial cell dysfunction results in reduced production of vasodilators, such as nitric oxide and prostacyclin, and over production of vasoconstrictors, such as thromboxane A2 and endothelin-1 (ET-1), nitric oxide, and prostacyclin have been the principal focus of research into new treatment options for patients with PAH.

Symptoms:

Symptoms can include:

    Breathlessness (dyspnea), particularly on physical activity.

  • Fatigue.

  • Dizziness.

  • Syncope, also on physical activity (rare).

  • Peripheral edema.

  • Chest pain, again particularly during physical activity.

Diagnosis:

There is not one specific way to diagnose PAH. In early stages of the disease, a physical exam may be normal or almost normal. It may take your doctor several months to diagnose PAH. A doctor who suspects a patient may have PAH usually runs a series of tests to measure blood pressure in the pulmonary arteries, decide how well the heart and lungs are working, and rule out other diseases.

Tests include:

    Chest X-ray (of the heart and lungs).

  • Electrocardiogram (an electrical measure of your heart rate and how regularly your heart is beating).

  • Transthoracic Doppler-echocardiography (TTE).

  • High resolution computed tomography (HRCT).

  • Vasoreactivity testing.

  • Pulmonary function tests (breathing tests that measure lung function).

  • Perfusion lung scan (an image that shows blood flow through the lungs).

  • Six-minute walk test (a measure of the patient's ability to do exercise).

  • Pulmonary angiography.

  • Right-heart catheterization (a special device that the doctor threads through a vein into the heart and arteries of the lungs to measure pressure in the arteries and test how well the heart is pumping).

Treatment:

There is no cure for PAH, but there are several treatment options. Treatments include medications and surgery; patients also make lifestyle changes as their PAH worsens and limits daily activity. Treatments for PAH aim to reduce symptoms, improve quality of life, and slow down how quickly the disease progresses.

Types of medications your doctor may prescribe to ease symptoms include:

    Endothelin receptor antagonists (ERAs) to stop the harmful effects of endothelin, a hormone that helps control blood flow and cell growth in blood vessels. Patients with PAH often have high levels of endothelin.

  • Phosphodiesterase-5 inhibitors (PDEI) to relax the muscles and reduce abnormal cell growth in blood vessels.

  • Prostacyclins to relax blood vessels, reduce abnormal cell growth, and help prevent blood clots.

  • Anticoagulants to prevent blood clots in the lungs.

  • Calcium channel blockers to reduce constriction in the pulmonary arteries.

  • Diuretics to improve how effectively the heart works by reducing the volume of blood it must pump.

  • Digoxin to help the heart pump more forcefully.

  • Inhaled oxygen to reduce shortness of breath.

Surgical options:

    Lung or heart-lung transplantation - Patients who fail standard therapies may be candidates for heart-lung transplantation. Transplantation can be lifesaving, but the supply of donor organs is very limited.

  • Atrial septostomy - In this treatment, a surgeon creates a hole between the top chambers of the heart. This allows blood to be pumped to the rest of the body without going through the lungs first. This can reduce strain on the heart, but it also greatly reduces the amount of oxygen that can be delivered to the body.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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