Pulmonary hypertension thresholds: time to lower further?

Abstract

Since the first World Symposium on Pulmonary Hypertension in 1973, pulmonary hypertension has been arbitrarily defined as mean pulmonary arterial pressure (PAP) of at least 25 mm Hg at rest. This conservative threshold minimised the risk of overdiagnosis and overtreatment of pulmonary hypertension. However, evidence has since shown that the mean PAP in the general population is 14·0 mm Hg (SD 3·3), 1 Kovacs G Berghold A Scheidl S et al. Pulmonary arterial pressure during rest and exercise in healthy subjects: a systematic review. Eur Respir J. 2009; 34: 888-894 Crossref PubMed Scopus (624) Google Scholar suggesting that 20 mm Hg should be considered as above the upper limit of normal (ie, above the 97·5th percentile). This finding led to a newer, evidence-based, haemodynamic definition of pulmonary hypertension as a mean PAP of more than 20 mm Hg. 2 Simonneau G Montani D Celermajer DS et al. Haemodynamic definitions and updated clinical classification of pulmonary hypertension. Eur Respir J. 2019; 531801913 Crossref PubMed Scopus (1114) Google Scholar Precapillary pulmonary hypertension, generally seen in patients with pulmonary arterial hypertension, pulmonary hypertension due to chronic lung diseases or chronic thromboembolism, and a subset of patients with pulmonary hypertension due to left heart disease, was also characterised by the concomitant presence of pulmonary artery wedge pressure of 15mm Hg or less and pulmonary vascular resistance (PVR) of 3 Wood units or more. 2 Simonneau G Montani D Celermajer DS et al. Haemodynamic definitions and updated clinical classification of pulmonary hypertension. Eur Respir J. 2019; 531801913 Crossref PubMed Scopus (1114) Google Scholar The PVR threshold was already recognised as conservative and somewhat arbitrary, because preliminary data suggested the upper limit of normal for PVR could be around 2 Wood units. 1 Kovacs G Berghold A Scheidl S et al. Pulmonary arterial pressure during rest and exercise in healthy subjects: a systematic review. Eur Respir J. 2009; 34: 888-894 Crossref PubMed Scopus (624) Google Scholar Pulmonary vascular resistance and clinical outcomes in patients with pulmonary hypertension: a retrospective cohort studyThese data widen the continuum of clinical risk for mortality and heart failure in patients referred for RHC with elevated pulmonary artery pressure to include PVR of around 2.2 Wood units and higher. Testing the generalisability of these findings in at-risk populations with fewer cardiopulmonary comorbidities is warranted. Full-Text PDF