Exercise Pathophysiology in Pulmonary Arterial Hypertension—The Physiologic Explanation for Why Pulmonary Arterial Hypertension Does What It Does

Pulmonary arterial hypertension (PAH) is a chronic disease that is associated with a significant and progressive limitation of exercise tolerance. The pathophysiological mechanisms of exercise intolerance during exercise are complex, multifactorial, and in fact not limited to the pulmonary circulation and the right ventricle. Disturbance of autonomic nervous function leads to an enhanced chemosensitivity, as well as respiratory and peripheral muscle weakness, and systemic endothelial dysfunction, which together play important roles in PAH pathophysiology and symptomatology. This article is focused on the different pathophysiological mechanisms of exercise intolerance in PAH, their interactions, and their relevance for clinical practice.