Fig. 1From: Unraveling the epigenetic landscape of pulmonary arterial hypertension: implications for personalized medicine developmentClinical 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. HFÂ heart failure, LVEF left ventricular ejection fraction, mPAPÂ mean pulmonary arterial pressure, PAHÂ pulmonary arterial hypertension, PAWPÂ pulmonary arterial wedge pressure, PVRÂ pulmonary vascular resistance, and WUÂ wood units. Created with BioRender.comBack to article page