Clinical phenotypes and the risk factors of mild pulmonary hypertension

The definition of pulmonary hypertension (PH) was revised as mean pulmonary arterial pressure (mPAP) >20 mmHg from ≥25 mmHg in the recent PH guidelines; however, the characteristics of PH patients with mPAP 21-24 mmHg have not been well described.

A total of 1080 individuals who underwent right heart catheterization (2018-2022) was categorized into 3 groups by mPAP: no PH with mPAP ≤20 mmHg, mild PH with mPAP 21-24 mmHg, and conventional PH with mPAP ≥25 mmHg. We assessed PH subtypes of hemodynamic and clinical classification and compared survival outcomes (all-cause mortality, heart failure hospitalization, lung transplant) using Cox models.

Of them, 391 patients (36.2%) were diagnosed as PH including mild PH (n = 137) and conventional PH (n = 254). Phenotypically, mild PH was predominantly characterized by pre-capillary hemodynamics and Group 2 clinical classification. Mild PH is associated with an intermediate prognosis: outcomes are more favorable than in conventional PH but inferior to no PH (HR 1.74 [95% CI 1.15-2.61]). While the two PH phenotypes appear to share comorbidity-related factors, hemodynamic parameters were associated with survival outcomes not in mild PH but in conventional PH.

The observation that mild PH constitutes approximately one-third of overall PH cases carries substantial clinical weight. The newly identified mild PH cohort was characterized mainly by pre-capillary and Group 2 subtypes. While mild PH is associated with an intermediate prognosis, comorbidities appear to be the primary determinant of outcomes in this group, unlike in conventional PH where hemodynamics play a larger role.