Cardiopulmonary exercise testing allows the assessment of the integrative cardiopulmonary response to exercise and is a useful tool to assess the underlying pathophysiologic mechanisms leading to exercise intolerance. Patients with pulmonary hypertension often face a considerable delay in diagnosis due to the rarity of the disease and nonspecific symptoms of dyspnea, fatigue, and exercise limitation. Cardiopulmonary exercise testing may be suggestive of pulmonary hypertension in patients with evidence of both circulatory impairment and ventilatory inefficiency. Other factors, such as mechanical ventilatory constraints from dynamic hyperinflation and peripheral muscle dysfunction, contribute to the profound dyspnea during exercise experienced by many patients with pulmonary hypertension. In patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension, several exercise variables, such as low peak [Formula: see text]o, high Vd/Vt, and high [Formula: see text]e/[Formula: see text]co, have proven to be useful in establishing the severity of functional impairment, predicting prognosis, and assessing the efficacy of interventions.

In normal coronary arteries, several different mechanisms of blood flow regulation exist, acting at different levels of the coronary tree: endothelial, nervous, myogenic and metabolic regulation. In addition, physiologic blood flow regulation is also dependent on the activity of several coronary ion channels, including ATP-dependent K(+) channels, voltage-gated K(+) channels and others. In this context, ion channels contribute by matching demands for homeostatic maintenance. They play a primary role in rapid response of both endothelium and vascular smooth muscle cells of larger and smaller arterial vessels of the coronary bed, leading to coronary vasodilation. Consequently, an alteration in ion channel function or expression could be directly involved in coronary vasomotion dysfunction.

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Despite recent advances in the therapeutic management of patients affected by pulmonary arterial hypertension (PAH), survival remains poor. Prompt identification of the disease, especially in subjects at increased risk of developing PAH, and prognostic stratification of patients are a necessary target of clinical practice but remain challenging. Cardiopulmonary exercise test (CPET) parameters, particularly peak oxygen uptake, end-tidal carbon dioxide tension and the minute ventilation/carbon dioxide production relationship, emerged as new prognostic tools for PAH patients. Moreover, CPET provides a comprehensive pathophysiological evaluation of patients' exercise limitation and dyspnoea, which are the main and early symptoms of the disease. This review focuses on the role of CPET in the management of PAH patients, reporting guideline recommendations for CPET and discussing the pathophysiology of exercise limitation and the most recent use of CPET in the diagnosis, prognosis and therapeutic targeting of PAH.