Fig. 1

Clinical classification of pulmonary hypertension. The World Health Organization classifies PH into five groups based on its etiology, clinical presentation, hemodynamics, and characteristics. Group 1 includes pulmonary arterial hypertension (PAH), which is idiopathic, heritable, or associated with conditions such as connective tissue disease, congenital heart disease, HIV infection, or portal hypertension. Group 2 includes PH due to left heart disease. This type of PH is caused by left ventricular (LV) dysfunction or valvular disease. Group 3 includes PH due to lung diseases and/or hypoxia, such as chronic obstructive pulmonary disease, interstitial lung disease, and sleep-disordered breathing. Group 4 includes chronic thromboembolic pulmonary hypertension caused by recurrent thromboembolic occlusion of the pulmonary arteries. Group 5 includes PH with unclear and/or multifactorial mechanisms. Classification of PH is crucial for accurate diagnosis, appropriate treatment, and a better understanding of the pathophysiology of the disease. HF heart failure, LVEF left ventricular ejection fraction, mPAP mean pulmonary arterial pressure, PAH pulmonary arterial hypertension, PAWP pulmonary arterial wedge pressure, PVR pulmonary vascular resistance, and WU wood units. Created with BioRender.com