Ghio S, et al. - New definitions of pulmonary hypertension (PH) in left heart disease have been proposed in the most recent European guidelines. Researchers, in turn, studied if different hemodynamic definitions of post-capillary PH imply a different reversibility of PH in response to acute vasodilator administration in heart failure patients with reduced ejection fraction and PH (HFrEF-PH). In combined post-capillary and pre-capillary pulmonary hypertension patients, substantial improvements in pulmonary vascular resistance (PVR), diastolic pulmonary gradient, and transpulmonary gradient were observed after acute vasodilator administration, however, this response was associated with persistent abnormalities in the PVR vs pulmonary compliance relationship.