Pulmonary Arterial Stiffness Related to mPAP and Heart Rate in Idiopathic PAH

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PA stiffness could not be determined based on pulmonary vascular resistance, which may call into question the widely accepted paradigm of RC-time constancy.
PA stiffness could not be determined based on pulmonary vascular resistance, which may call into question the widely accepted paradigm of RC-time constancy.

In a large population of patients with untreated idiopathic pulmonary arterial hypertension (PAH), PA stiffness was related to mean pulmonary arterial pressure (mPAP) and heart rate, and this association was stronger than that of age and sex, according to a study published in CHEST.

Denis Chemla, MD, of the Service de Physiologie, Hôpital Bicêtre, AP-HP in Le Kremlin- Bicêtre, France, and colleagues, retrospectively reviewed data from patients diagnosed with idiopathic PAH by right heart catheterization enrolled in the French PAH Network registry between 2006 and 2016, with baseline data that made calculating PA stiffness possible.

The goal of the study was to document PA stiffness and its primary correlates and to test the hypothesis that PA stiffness may be influenced by mPAP, heart rate, age, and sex, and may increase with disease severity. It is known that increases in pulmonary vascular resistance (PVR) correlate well with increases in PA stiffness. A secondary goal of the study was to test whether or not total arterial compliance (C) could be calculated on the basis of PVR alone. The final goal was to determine the prognostic significance of PA stiffness at diagnosis of PAH.

The analysis included 719 patients. While arterial stiffness increased with mPAP and heart rate and was higher in the five high-risk patient subgroups as defined by the European Society of Cardiology/European Respiratory Society guidelines, it was not affected by age or sex. PA stiffness could not be determined based on PVR, which the investigators suggested calls into question the widely accepted paradigm of RC-time (the PVR x C product) constancy. Furthermore, PA stiffness at baseline did not provide independent prognostic information.

The researchers noted that in addition to the high-strain-induced stiffening that was a result of increased mPAP, two other mechanisms may be involved in PA stiffness — chronic stiffening due to wall thickening and vascular remodeling of the extracellular matrix, involving loss of elastin and increase in collagen content, and stiffening from smooth muscle cell responses.

Although women are disproportionally affected by idiopathic PAH, PA stiffness was similar in both women and men, which the researchers stated was unexpected. They suggested that these findings warrant further confirmation in other PAH populations.

Disclosures: Dr Weatherald reports financial relationships with Actelion, Bayer, ad Novartis. Dr Boucly reports nonfinancial support from Bayer, Merck Sharp & Dohme, and GlaxoSmithKline as well as personal fees from Actelion. Drs Jaïs and Sitbon have received speaker and consultancy fees from Actelion, Bayer, GlaxoSmithKline, and Merck.

Reference

Chemla D, Weatherald J, Lau EMT, et al. Clinical and hemodynamic correlates of pulmonary arterial stiffness in incident, untreated patients with idiopathic pulmonary arterial hypertension [published online June 22, 2018]. CHEST. doi:10.1016/j.chest.2018.06.015

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