Background The definition of pulmonary hypertension (PH) has undergone notable changes.

Objectives To evaluate the effect of the new PH definition in patients with lung disease enrolled in the REHAR registry (Spanish registry of PH in lung disease, n=500).

Methods We stratified patients according to:

6th World Symposium on PH (6WSPH):
- No PH (NoPH): mean pulmonary artery pressure, mPAP, <21 mmHg or 21-24 mmHg and pulmonary vascular resistance, PVR, <3 wood units, WU.

- Moderate PH (MPH): mPAP 21-24 mmHg and PVR, ?3 WU; or mPAP ?25 mmHg.

- Severe PH (SPH): mPAP ?35 mmHg or mPAP 25-34 mmHg and cardiac index, CI, <2 L/min/m2

European Society of Cardiology/European Respiratory Society (ESC/ERS) PH guidelines 2022:
-  Unclassifiable PH (UPH): mPAP >20 mmHg with PVR ?2 WU and pulmonary artery wedge pressure, PAWP ?15 mmHg

- MPH: mPAP >20 mmHg and PVR 2.5-5 WU, PAWP ?15 mmHg

- SPH: mPAP >20 mmHg and PVR >5 WU, PAWP ?15 mmHg

Results Five patients had incomplete data; of the remaining 495 patients, 242 had COPD, 226 interstitial lung disease, 16 bronchiectasis, 11 had other diagnoses.

According to 6WSPH, there were 10 NoPH patients, 287 MPH, 185 SPH; 13 cases were not classifiable. According to ESC/ERS 2022 guidelines, 26 patients had UPH, 257 MPH and 184 SPH, 13 had post-capillary PH and 15 combined pre/post-capillary PH.

The proportion of patients with MPH and SPH was similar in both definitions, but our analysis shows that 30% (n =146) of cases changed status. Survival was associated with severity in both definitions.

Conclusions With the change of PH definition, 30% of patients change severity status and its association with patients characteristics needs to be further explored.