Pulmonary hypertension overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], 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.
Classification
Pulmonary hypertension has been previously divided into two categories: primary (currently known as idiopathic pulmonary arterial hypertension (IPAH)) and secondary. However; given the fact that some subcategories of secondary pulmonary hypertension share several similarities with primary pulmonary hypertension in terms of pathology, progression and response to therapy, the WHO (World Health Organization) has based its reclassification of pulmonary hypertension on the mechanism of the disease.
Pathophysiology
Pulmonary hypertension was first identified by Dr. Ernst von Romberg in 1891.[1] 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.
Causes
The most common cause of pulmonary hypertension is left heart failure leading to pulmonary venous hypertension. Common causes of pulmonary arterial hypertension (PAH) include HIV, systemic sclerosis, portal hypertension, sickle cell disease,[2] and congenital heart disease. Lung diseases that lower oxygen in the blood (hypoxia) are well known causes of pulmonary hypertension, including COPD, interstitial lung disease, Pickwickian syndrome or obesity-hypoventilation syndrome, and obstructive sleep apnea.
Differential Diagnosis
One of the most common initial presentations of patients with pulmonary hypertension is dyspnea; therefore, the differential diagnosis is very broad. As the disease progresses with time, more symptoms related to right ventricular hypertrophy and failure occur; which further narrows down the differential diagnosis.[3]
Epidemiology
While previously considered a rare disease, the most recent evidence from a French registry suggests that the incidence of new cases of pulmonary arterial hypertension is 2-3 cases per million per year.
Risk Factors
Pulmonary hypertension can be diagnosed in people of all ages, races, and ethnicity. However some risk factors make some people more likely to get the disease.
History and Symptoms
- 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.
Physical Exam
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.
Laboratory Tests
EKG
Chest X-Ray
CT scan
Echocardiography
Right Heart Catherization
Treatment
Prior to the initiation of therapy for pulmonary hypertension, a right heart catheterization should be performed to exclude (as a cause of the pulmonary hypertension. If type II pulmonary hypertension is confirmed than a vasodilator challenges performed to assess the reactivity of the pulmonary vasculature. If the pulmonary vasculature is reactive, then calcium channel blockers may be an appropriate therapy. If the pulmonary vasculature is not reactive than endothelin antagonist and processed annoyance are the optimal management. Patients with eisenmenger syndrome should not be administered calcium channel blockers. Pulmonary functions tests, imaging studies(V/P scan), and arterial oxygen saturation should also be obtained for every patient with PAH, in order to plan the therapy accordingly. If the patients fails to respond to medical therapy, surgery is considered.
Medical Therapy
Surgery
Primary Prevention
Natural History, Complications and Prognosis
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.
References
- ↑ Romberg E von. Über Sklerose der Lungenarterie. Dtsch Arch Klin Med 1891-1892;48:197-206.
- ↑ Gladwin MT, Sachdev V, Jison ML, Shizukuda Y, Plehn JF, Minter K, Brown B, Coles WA, Nichols JS, Ernst I, Hunter LA, Blackwelder WC, Schechter AN, Rodgers GP, Castro O, Ognibene FP. Pulmonary hypertension as a risk factor for death in patients with sickle cell disease. N Engl J Med 2004;350:886-95
- ↑ Doi S (2008). "[Differential diagnosis of pulmonary hypertension]". Nihon Rinsho. 66 (11): 2127–32. PMID 19051731.