15 February 2020 by Seshika Ratwatte

Pulmonary arterial hypertension with below threshold pulmonary vascular resistance

Pulmonary vascular resistance (PVR) >3 Wood Units (WU) is a criterion of the haemodynamic definition of pulmonary arterial hypertension (PAH). However, this conservative cut-off is not evidence based. Data is lacking on the natural history, response to therapy and survival of patients diagnosed with precapillary pulmonary hypertension with mild elevation of PVR.

Using the Australian and New Zealand Pulmonary Hypertension Registry, we analysed outcomes of this unique group treated with PAH therapy between 2004-2017. Treatment for PAH could be prescribed solely on the basis of mPAP and PAWP in Australia. Thus, we studied patients with mPAP≥25 mmHg, PAWP≤15mmHg but PVR<3WU.

82 patients met the haemodynamic inclusion criteria (mean age 63±11 years; 67 females). Underlying aetiologies included idiopathic disease (n=39), connective tissue disease (n=42) and HIV infection (n=1). At diagnosis, mPAP was 27mmHg (IQR25-30), PAWP 13mmHg (IQR11-14) and PVR 2.2WU (IQR1.9-2.7). Baseline 6MWD was 352m (IQR280-416) and 77% were in NYHA 3 or 4 functional class. All patients were commenced on monotherapy with an endothelin receptor antagonist (n=66) or phosphodiesterase-5 inhibitor (n=16). At first re-evaluation (median 5 months; IQR4-12), 6MWD increased by 46m (IQR7-96) and 35% demonstrated improvement in NYHA functional class. After a median follow-up of 65 months (IQR32-101), 18/82 (22.0%) had died, with estimated 1-yr and 5-yr survivals of 98% and 84%, respectively. Death attributed to PAH occurred in 6/18 (33.3%) of these patients. Patients with precapillary PH and “borderline” PVR have adverse outcomes. Such patients appear to respond to PAH therapy but this requires further study in randomised trials.

About the author

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Seshika Ratwatte

Cardiology Advanced Trainee

Concord Hospital


Key Contributors

Seshika Ratwatte, James Anderson, Geoffrey Strange, Carolyn Corrigan, Nicholas Collins, David S Celermajer, Nathan Dwyer8, John Feenstra, Dominic Keating, Eugene Kotlyar, Melanie Lavender, Helen Whitford, Ken Whyte, Trevor Williams, Jeremy Wrobel, Anne Keogh and Edmund M. Lau MBBS7 on behalf of the PHSANZ Registry. Department of Cardiology, Concord Repatriation and General Hospital; Royal Prince Alfred Hospital; University of Newcastle, Australia, Respiratory Department, Sunshine Coast Hospital, School of Medicine, University of Notre Dame, Fremantle, Australia, Pulmonary hypertension Society of Australia and New Zealand, Heart Transplant Unit, St Vincent's Hospital, Darlinghurst, Australia; Department of Cardiology, John Hunter Hospital, Newcastle, Australia; Sydney Medical School, University of Sydney; Royal Prince Alfred Hospital, Camperdown, Australia; Department of Cardiology, Royal Hobart Hospital, Hobart, Australia; Queensland Lung Transplant Service, Prince Charles Hospital, Chermside, Australia; Department of Allergy, Immunology and Respiratory Medicine, The Alfred Hospital, Melbourne, Australia; Heart Transplant Unit, St Vincent's Hospital, Darlinghurst, Australia; Advanced Lung Disease Unit, Fiona Stanley Hospital, Murdoch, Australia; Greenlane Clinical Centre, Auckland City Hospital, Auckland, New Zealand;

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