Gaps of evidence in pulmonary arterial hypertension

•The most important and controversial areas in PAH are the definition and correct classification of pulmonary hypertension and its impact on the clinical ground, the limitations of the current risk stratification tools and the therapeutic approach.•A mild increase in mPAP may be caused by different factors such as left heart diseases and lung diseases, thus clinicians have to recognize the underlying disease and optimize its treatment.•Risk stratification models in PAH need to be improved, including individual genetic profile and evaluation of right ventricular function.•PAH patients treated with oral combination therapies need a strict follow-up to avoid the delay of parenteral prostanoids that could have a detrimental effect on prognosis.