Exercise-induced pulmonary hypertension: rationale for correcting pressures for flow and guide to non-invasive diagnosis

Exercise-induced pulmonary hypertension (exPHT) is a haemodynamic condition linked to increased morbidity and mortality across various cardiopulmonary diseases. Traditional definitions of exPHT rely on absolute cut-offs, such as mean pulmonary artery pressure (mPAP) above 30 mmHg during exercise. However, recent research suggests that these cut-offs may not accurately reflect pathophysiological changes, leading to false positives and false negatives. Instead, the mPAP over cardiac output (CO) slope, which incorporates both pressure and flow measurements, has emerged as a more reliable indicator. A slope exceeding 3 mmHg/L/min is now considered diagnostic for exPHT and strongly correlates with adverse outcomes. Stress echocardiography serves as a viable alternative to invasive assessment, enabling broader implementation. This review discusses the physiological basis of pulmonary haemodynamics during exercise, the advantages of the mPAP/CO slope over absolute pressure measurements, the evidence supporting its inclusion in clinical guidelines, and provides a practical guide for non-invasive determining the mPAP/CO slope in clinical practice.