Pulmonary arterial hypertension: classification, diagnosis and contemporary management

Positioned between the two sides of the heart and residing within the lungs, the pulmonary circulation has a central role in cardiopulmonary gas exchange and oxygen transport. Its central position also renders the pulmonary circulation prone to injury as a result of disorders affecting the heart, lungs or systemic circulation. An uncommon, but serious and potentially devastating chronic disorder of the pulmonary circulation is pulmonary hypertension, a haemodynamic abnormality of diverse aetiology and pathogenesis. Over the past decade, several advances have occurred in the understanding, classification and medical management of pulmonary hypertension.1 This article outlines the approach to the diagnosis of pulmonary arterial hypertension (PAH) and discusses the use of currently available drug treatments and surgical procedures for this condition. We searched the Cochrane Controlled Trials Register, PubMed and Medline (MESH terms: primary pulmonary hypertension and pulmonary arterial hypertension) for clinical trials, randomised controlled trials, meta-analyses, practice guidelines and reviews. We selected only studies on humans and articles written in English. Pulmonary hypertension was previously divided into primary and secondary categories; primary pulmonary hypertension described an idiopathic hypertensive vasculopathy exclusively affecting the pulmonary circulation, whereas secondary pulmonary hypertension was associated with a causal underlying disease process. The recent identification of a gene responsible for the inherited forms of this disease, along with the development of specific medical treatments and the refinement of surgical techniques, has prompted a revised classification of pulmonary hypertension. This classification distinguishes conditions that directly affect the pulmonary arterial tree from those primarily affecting the pulmonary venous system or respiratory structure and function2 (box 1). The term primary pulmonary hypertension has now more accurately been replaced by idiopathic PAH, or, when supported by genetic investigation, familial PAH; the term secondary pulmonary hypertension has been abandoned. ### Box 1: Classification of pulmonary arterial hypertension

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