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Pulmonary hypertension
In medicine, pulmonary hypertension (PH) or pulmonary artery hypertension (PAH) is an increase in blood pressure in the pulmonary arteryor lungvasculature. Depending on the cause, it can be a severe disease with a markedly decreased exercise tolerance and right-sided heart failure. It was first identified by Dr Ernst von Romberg in 1891[{{fullurl:Template:FULLPAGENAME}}#endnote_Romberg].
Signs and symptomsA history usually reveals gradual onset of shortness of breath, fatigue, angina pectoris, syncope(fainting) and peripheral edema. In order to establish the cause, the physician will generally conduct a thorough medical history and physical examination. A detailed family history is taken to determine whether the disease might be familial. DiagnosisNormal pulmonary arterial pressure in a person living at sea level has a mean value of 12-16mmHg. Definite pulmonary hypertension is present when mean pressures at rest exceed 25 mmHg. Although pulmonary arterial pressure can be estimated on the basis of echocardiography, pressure sampling with a Swan-Ganz catheterprovides the most definite measurement. Diagnostic tests generally involve blood tests, electrocardiography, arterial blood gasmeasurements, X-raysof the chest (generally followed by high-resolution CT scanning). Biopsy of the lung is usually not indicated unless the pulmonary hypertension is thought to be secondary to an underlying intrinsic lung disease. Clinical improvement is often measured in a "six-minute walking test", i.e. the distance a patient can walk in six minutes, and stability and improvements in this measurement correlate with reduced mortality. Causes and mechanismsPulmonary hypertension can be primary (occurring without an obvious cause) or secondary (a result of other disease processes.) Primary PHPrimary pulmonary hypertension (PPH) is considered a genetic disorder. Certain forms of PPH have been linked to mutations in the BMPR2 gene, which encodes a receptorfor bone morphogenic proteins[{{fullurl:Template:FULLPAGENAME}}#endnote_Deng], as well as the 5-HT(2B) gene, which codes for a serotoninreceptor[{{fullurl:Template:FULLPAGENAME}}#endnote_Blanpain]. Recently, characteristic proteins of human herpesvirus8 (also known for causing Kaposi sarcoma) were identified in vascular lesions of PPH patients[{{fullurl:Template:FULLPAGENAME}}#endnote_Cool]. However, it is not understood what roles these genes and viral particles play in PPH. PPH has also been associated to the use of appetite suppressants(e.g. Fen-phen)[{{fullurl:Template:FULLPAGENAME}}#endnote_Abenhaim]. While genetic susceptibility to adverse drug reactions is suspected, the cause of the disease is still largely unknown. PPH is very rare but often fatal. Patients usually have no symptoms until they reach their late twenties or early thirties. It is characterized by elevated pulmonary vascular resistanceattributable to the abnormal thickening of the vessel wall and narrowing of the lumenof arteriolesin the lungs. Secondary PHSecondary pulmonary hypertension (SPH) is often due to chronic obstructive pulmonary disease(COPD). Other factors that have been linked to secondary pulmonary hypertension are:
A common consequence of chronic pulmonary hypertension is cor pulmonale(right sided heart failure) believed to be caused by the increased load on the right ventricleand atriumof the heart. A chest radiograph(X-ray) will often reveal an enlarged right atrium and ventricle, and prominent pulmonary arteries. An ECGwill often demonstrate right ventricular hypertrophyor strain. Oedemaand fluid retentionfollow. ClassificationIn 2003, the 3rd World Symposium on Pulmonary Hypertension was convened in Venice to modify classification based on the new understanding of disease mechanisms. The revised system developed by this group provides the current framework for understanding pulmonary hypertension. The system includes several improvements over the former 1998 Evian Classification system. The terms "primary" and "secondary" were discontinued because they had limited diagnostic value. In addition, new classifications were added, including primary veno-occclusive disease(PVOD). Risk factor descriptions were updated, and the classification of congenital systemic-to pulmonary shunts was revised. A new classification of genetic factors in PH was recommended, but not implemented because available data were judged to be inadequate. The Venice 2003 Revised Classification system can be summarized as follows[{{fullurl:Template:FULLPAGENAME}}#endnote_Venice]:
These terms are currently in use, but they are not yet as commonly used as the old terms of PPH and SPH. EpidemiologyWomen are almost twice as likely to present with PPH than men. The annual incidence is about 1 in 1,000,000. TreatmentTreatment is determined by the condition underlying the cause of the hypertension. For instance, long term oxygen therapy has been proven to be useful in patients with chronic obstructive pulmonary disease, and when the pulmonary hypertension is due to chronic thromboembolism, inferior vena cavalfilter insertion or pulmonary endarterectomy can be performed. In PPH, lifestyle changes, digoxin, diuretics, oral anticoagulants, oxygen therapy and vasodilatorsare the mainstays of treatment. Synthetic prostacyclin(an eicosanoid) per continuous infusion is commonly used in PAH. Prostacyclin is available in three forms: by catheter (Flolan®), subcutaneously (Remodulin®), and recently approved is an inhaled version , iloprost(Ventavis®). There are two oral medications, bosentan(marketed as Tracleer®), an endothelinreceptor antagonist and sildenafil, better known for its effects on erectile dysfunction, was approved in 2005. Two new oral medications are in the final stages of approval: sitaxsentanand ambriesatan. Pulmonary thromboendarterectomy (PTE) is a surgical procedure that is used when pharmaceutical management fails. It is the surgical removal of thrombus(clot) and the lining of the pulmonary artery; it is a large and difficult procedure which is currently performed in San Diego, California. Case series show remarkable success in selected patients. PrognosisSeveral studies have reported a mean survival without treatment of 2-3 years from time of diagnosis with the cause of death usually being right ventricular failure (cor pulmonale). References
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