Pulmonary hypertension overview

, Richard Channick, M.D.; Assistant Editor(s)-in-Chief: Lisa Prior, Ann Slater, R.N.

Overview
Pulmonary hypertension (PH) is an increase in blood pressure in the pulmonary artery or lung vasculature, leading to shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by exertion.

Although the terms primary pulmonary hypertension (meaning of unknown cause) and secondary pulmonary hypertension (meaning due to another medical condition) still persist in materials disseminated to patients and the general public, these terms have largely been abandoned in the medical literature. This change has occurred because the older dichotomous classification did not reflect pathophysiology or outcome. It led to erroneous therapeutic decisions, i.e. treat "primary" pulmonary hypertension only. This in turn led to therapeutic nihilism for many patients labeled "secondary" pulmonary hypertension, and could have contributed to their deaths. The term "primary pulmonary hypertension" has now been replaced with "idiopathic pulmonary arterial hypertension". The terms "primary" and "secondary" pulmonary hypertension should not be used any longer.

Pathophysiology

 * Pulmonary hypertension was first identified by Dr. Ernst von Romberg in 1891. It can be one of five different types, arterial, venous, hypoxic, thromboembolic, or miscellaneous.


 * Whatever the cause is, an initiating factor leads to increased resistance in the pulmonary vasculature. As a consequence, the right ventricle adapts by increasing right ventricular systolic pressures. This will subsequently result in stiffer vessels, further increasing the blood pressure within the lungs and impairing blood flow.


 * Pulmonary hypertension mainly affects small vessels and the main histological findings include intimal hyperplasia and medial hypertrophy.


 * BMPR2 and Activin-like kinase 1 are two mutations implicated in the pathogenesis of familial pulmonary arterial hypertension.

Clinical presentation:

 * Depending on the cause, pulmonary hypertension can be a severe disease with a markedly decreased exercise tolerance and right-sided heart failure.
 * A detailed clinical history and physical exam are very important to start with looking for typical signs and symptoms of pulmonary hypertension.


 * A history usually reveals gradual onset of shortness of breath, fatigue, non-productive cough, angina pectoris, fainting or syncope, peripheral edema, and rarely hemoptysis.


 * A physical examination is performed to look for typical signs of pulmonary hypertension. These include extra heart sounds, murmurs and signs of RV failure.


 * A comprehensive past medical history, medication history, family and social history and review of systems are also essential and may reveal further clues about the etiology of the condition.

Diagnostic tests:

 * Some diagnostic tests are required to confirm the presence of pulmonary hypertension and exclude other possible diagnoses. These generally include pulmonary function tests, blood tests, electrocardiography (ECG), arterial blood gas measurements, chest x-ray, and V/Q scanning to exclude chronic thromboembolic pulmonary hypertension.


 * Clinical improvement is often measured by a "six-minute walk test", i.e. the distance a patient can walk in six minutes. Stability and improvement in this measurement correlate with better survival.
 * Pressure sampling with a swan-Ganz catheter provides the most definite measurement of pulmonary arterial pressure, therefore diagnosis of PAH requires a cardiac catheterization. A swan-Ganz catheter can also measure the cardiac output which can give us an idea about the severity of this condition.

Treatment:

 * All patients suspected to have pulmonary hypertension should undergo several diagnostic tests to find the true etiology of pulmonary hypertension. After confirming the diagnosis and etiology, the physician starts by general measures and lifestyle changes. Then, a vasoreactivity test is performed to assess the patients response to vasodilators and according to that medical therapy is initiated.
 * Specific Drug Therapies include calcium channel blockers, prostanoids, endothelin receptor antagonsit, and phosphodiesterase type-5 inhibitors.
 * If the patients fails to respond to medical therapy, surgery is considered.

Prognosis and survival:

 * Eventhough there is no cure for pulmonary hypertension, outcomes have changes dramatically during the past few decades.


 * Some indicators of poor prognosis include RV dysfunctions or failure, low cardiac index, pericardial effusion, and decreased exercise capacity.


 * According to an NIH registry, the median survival is 2.8years in patients who don't receive any treatment. This was found to be lower for patients with associated co-morbidities.