Box 1 Definitions.

PH, according to the most recent, 6th WSPH (Nice, 2018)

mPAP >20 mmHg in children >3 months of age at sea level

Pre-capillary PH (e.g., PAH)

mPAP >20 mmHg

PAWP ≤ or LVEDP ≤15 mmHg*

PVR ≥3 WU (PVR index ≥3 WU·m2 BSA in children)#

Diastolic TPG (DPG) ≥7 mmHg (adjunct criterion)

Isolated post-capillary PH (Ipc-PH) in adults, e.g., predominantly diastolic LV dysfunction (HFpEF)*

mPAP >20 mmHg

PAWP or LVEDP >15 mmHg

PVR <3 WU in adults (PVR index <3 WU·m2)

Diastolic TPG (DPG) <7 mmHg (adjunct criterion)

Combination of pre-capillary and post-capillary PH (Cpc-PH) in adults*

mPAP >20 mmHg

PAWP or left ventricular end-diastolic pressure (LVEDP) >15 mmHg

PVR ≥3 WU (PVR index ≥3 WU·m2 in children)

PAH

mPAP >20 mmHg

PAWP or LVEDP ≤15 mmHg*

PVR ≥3 WU (PVR index ≥3 WU·m2 in children), plus criteria for group 1 PH

Pulmonary Hypertensive Vascular Disease (PHVD)

For biventricular circulations

mPAP >20 mmHg and PVR ≥3 WU (PVR index ≥3 WU·m2 in children)

For circulations with cavopulmonary anastomosis (e.g., Fontan physiology)

Mean TPG >6 mmHg (calculate mPAP minus mLAP or PAWP) or PVR index >3 WU·m2

The classification of PH according to the World Symposium on PH (WSPH, Nice, 2018) (2). Detailed hemodynamic definitions of PH (e.g., value of the diastolic transpulmonary pressure gradient) can be found in the 2015 ESC/ERS guidelines (1), Hansmann G. J Am Coll Cardiol, 2017 (8) and Apitz et al. Heart, 2016 (12). It should be noted that even mildly elevated mPAP values (20–24 mmHg, prognostic threshold 17mmHg) are independent predictors of poor survival in adults with PH (Douschan et al. AJRCCM 2018) (13). In adults, PVR is not indexed to body surface area (BSA). Please note that the BSA has a large impact on the absolute numbers of systemic blood flow index (Qsi, cardiac index), pulmonary blood flow index (Qsi) and PVR index (PVRi), especially in either severely cachectic or very obese patients. ^#, PVR is calculated as mTPG divided by Qp, PVR index is calculatd as mTPG divided by Qp indexed to BSA. The mTPG (syn. DPD) is a pressure difference and calculated as mPAP minus mLAP or PAWP. *, in many instances, it is useful to measure the PAWP simultaneously with the LVEDP. LVEDP, left ventricular end-diastolic pressure; PH, pulmonary hypertension; BSA, body surface area; mPAP, mean pulmonary artery pressure; mLAP, mean left atrial pressure; PAH, pulmonary artery hypertension; PCWP, pulmonary capillary wedge pressure (syn. PAWP, pulmonary artery wedge pressure); PVR, pulmonary vascular resistance; TPG, transpulmonary pressure gradient; WSPH, World Symposium on Pulmonary Hypertension.