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Abstract In pulmonary arterial hypertension (PAH) patients it is essential to perform a prognostic assessment to optimize the treatment. The aim of this study is to evaluate the risk stratification concordance assessed with different exercise test variables in a cohort of PAH patients. A retrospective analysis was performed using patient data registered in the PAH unit. Only those patients in whom the mean time elapsed between the 6‐min walking test (6MWT) and the cardiopulmonary exercise test (CPET) was a maximum of 6 months were selected. A total of 140 records from 40 patients were finally analyzed. When it came to assessing the concordance between the two exercise tests in the guidelines (CPET and 6MWT), up to 84.3% of the records did not coincide in terms of the risk stratification. Exclusively considering the CPET parameters, most of the records (75%) failed to include all three variables in the same risk category. When analyzing the VO2 alone, up to 40.7% of the tests yielded different risk classifications depending on whether the parameter was expressed. In conclusion, there is a low concordance between the two proposed exercise tests. These results should be a call for reflection on whether the cut‐off points set for the exercise tests proposed for the current risk stratification are adequate to achieve a correct risk stratification or whether they require an appropriate revision.

Abstract A simplified 4‐strata risk stratification approach based on three variables is widespread in pulmonary arterial hypertension (PAH) at follow‐up. This study aimed to assess the impact of replacing the 6‐min walk test (6MWT) with the peak 02 uptake evaluated by the cardiopulmonary exercise test (CPET) on risk stratification by this scale. We included 180 prevalent patients with PAH from two reference hospitals in Spain, followed up between 2006 and 2022. Patients were included if all the variables of interest were available within a 3‐month period on the Spanish Registry of Pulmonary Arterial Hypertension (REHAP): functional class (FC); NT‐proBNP; 6MWT; and CPET. The original 4‐strata model (NT‐proBNP, 6MWT, FC) identified most patients at low or intermediate‐low risk (36.7% and 51.1%, respectively). Notably, the modified scale (NT‐proBNP, CPET, FC) improved the identification of patients at intermediate‐high risk up to 18.9%, and at high risk up to 1.1% in comparison with the previous 12.2% and 0.0% in the original scale. This new model increased the number of patients correctly classified into higher‐risk strata (positive NRI of 0.06), as well as classified more patients without events in lower‐risk strata (negative NRI of 0.04). The proposed score showed a slightly superior prognostic capacity compared with the original model (Harrel's C‐index 0.717 vs. 0.709). Using O2 uptake instead of distance walked in the 6MWT improves the identification of high‐risk patients using the 4‐strata scale. This change could have relevant prognostic implications and lead to changes in the specific treatment of PAH.