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INTRODUCTION

Pulmonary arterial hypertension (PAH) is a progressive disease of the pulmonary vasculature that results in right heart failure and excess morbidity and mortality without effective treatment. Although rapid progress has resulted in the availability of therapies that can improve the outlook for many patients, true full reversal of disease remains elusive. Furthermore, long delays in disease recognition are common, exposing patients to prolonged suffering and potentially irreversible harm. PAH should not be confused with other mechanisms leading to elevation of pulmonary arterial pressure, such as hypoxemic lung disorders (e.g., chronic obstructive pulmonary disease [COPD], interstitial lung disease [ILD]), left heart disease (e.g., systolic, diastolic, or valvular dysfunctions), or chronic thromboembolism.1,2 Prompt and accurate diagnosis of PAH followed by treatment based on the latest evidence-based guidelines are essential in successfully managing PAH.

CLASSIFICATION OF THE PULMONARY HYPERTENSIVE DISEASES

A “sclerosis of the pulmonary arteries” (“Uber Sklerose der Lungen Arterie”) without identifiable cause was first described by Ernst von Romberg in 1891.3 Exclusively descriptive reports of pathologic findings continued until the 1950s when the development of catheterization techniques allowed for hemodynamic evaluation. Using such methods, Dresdale et al. described a hypertensive vasculopathy of the pulmonary circulation involving vasoconstriction, elevation of pulmonary arterial pressure (PAP), and a measurable response to the injection of the nonselective α-adrenergic antagonist tolazoline.4 No cause could be identified for the pulmonary arteriopathy, and the term primary pulmonary hypertension (PPH) was introduced.5

Subsequent classification schemes for diseases causing pulmonary hypertension have been adopted by international consensus panels. These have evolved from systems based primarily on histopathologic findings to a current model that emphasizes the grouping of entities according to similarities in etiology and clinical characteristics (Table 72-1).6

TABLE 72-1Updated Classification of Pulmonary Hypertensiona

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