Patients with precapillary pulmonary hypertension (PH) and pulmonary vascular resistance (PVR) who do meet the definition of pulmonary arterial hypertension (PAH) may have functional limitations, adverse outcomes, and may benefit from PAH therapy, according to study results published in European Respiratory Journal.

A PVR of >3 Wood units (WU) is a criterion of the hemodynamic definition of PAH, however, this cut-off is conservative and arbitrarily defined. In Australia, PAH therapy can be prescribed solely on mean pulmonary artery pressure (mPAP) and pulmonary artery wedge pressure (PAWP) criteria, and data are lacking on the natural history, response to therapy, and survival of patients diagnosed with precapillary PH with mild or borderline elevation of PVR.

Therefore, using the Australian and New Zealand Pulmonary Hypertension Registry, researchers evaluated 82 patients diagnosed with PAH between January 2004 and December 2017 with the predefined hemodynamic characteristics of mPAP ≥ 25 mm Hg, PAWP ≤5 mm Hg, and PVR <3 WU. At diagnosis, mPAP was 27 mm Hg, PAWP 13 mm Hg, and PVR 2.2 WU. Baseline 6-minute walk distance (6MWD) was 352 m and 77% were considered New York Heart Association (NYHA) Functional Class 3 or 4.

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All patients began initial monotherapy with an endothelin receptor antagonist (n=66) or phosphodiesterase-5 inhibitor (n=16), and at first re-evaluation, 6MWD increased by 46 m and 35% of patients demonstrated improvement in NYHA functional class. After a median follow-up of 65 months, 18 of the 82 (22%) patients had died, with estimated 1-year and 5-year survival rates of 98% and 84%, respectively. Death attributed to PAH occurred in 6 of these 18 patients (7% of total cohort).

“Patients with precapillary PH and ‘borderline’ PVR falling outside the current definition have adverse outcomes,” the study authors wrote. “Such patients appear to respond to PAH therapy however this requires further study in randomised trials.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Ratwatte S, Anderson J, Strange G, et al. Pulmonary arterial hypertension with below threshold pulmonary vascular resistance [published online April 27, 2020]. Eur Respir J. doi:10.1183/13993003.01654-2019