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A1173 - Clinical and Hemodynamic Correlates of Pulmonary Arterial Stiffness in Incident, Untreated Patients with Idiopathic Pulmonary Arterial Hypertension
Author Block: D. Chemla1, J. C. Weatherald2, E. Lau3, L. Savale4, A. Boucly5, D. Montani6, M. Humbert7, O. Sitbon8, P. Herve9; 1Physiology, University Paris Sud, Le Kremlin Bicetre, France, 2Respirology, University of Calgary, Calgary, AB, Canada, 3Respiratory Medicine, Camperdown, Australia, 4Hopital Bicetre, Le Kremlin Bicetre, France, 5Hopital Bicêtre, Service de pneumologie et soins i, Le Kremlin-Bicêtre, France, 6Service de Pneumologie, Centre de reference de l'Hypertension Pulmonaire Sévère, Hopital de Bicetre, Le Kremlin Bicêtre, France, 7Pneumology, Hopital Bicetre, Bicetre, France, 8Service De Pneumologie, Hopital De Bicetre, 94270 - Le Kremlin - Bicetre, France, 9Hopital Marie Lannelongue, 92 Le Plessis Robinson, France.
Introduction: The role of decreased PA compliance (C) / increased PA stiffness (1/C) as a critical determinant of right ventricular dysfunction and prognosis has been emphasized in pulmonary arterial hypertension (PAH). Our aim was to document PA stiffness and its main correlates in a large population of incident, untreated patients.
Methods: We retrospectively reviewed all incident patients diagnosed with idiopathic PAH by right heart catheterization who were enrolled in the French PAH Network registry between 2006-2016 and who had complete baseline hemodynamic data allowing calculation of stiffness (PP/SV = PA pulse pressure / stroke volume index).
Results: In the 719 patients included (median age 66 years, 53.7% female), PA stiffness (median 1.49 mmHg×m2/mL [interquartile range 1.08 - 2.04 mmHg×m2/mL]) linearly increased with mean PA pressure (mPAP, r2=0.58). Stiffness was not influenced by age or sex and was higher in patients in the high vs low risk groups as defined by the European Society of Cardiology/European Respiratory Society guidelines. Pulmonary vascular resistance (PVR) was related to PA stiffness (positive linear relationship, r2=0.65) and to C (negative hyperbolic relationship, r2=0.60). The PVR×SV/PP product (RC-time) distribution was as variable as patient age and mPAP. The RC-time (median 650ms, IQR 546-768ms), age (66 years, 51-75) and mPAP (46mmHg, 39-54) were not normally distributed and exhibited similar values of their quartile coefficients of dispersion (0.17 / 0.19 / 0.16), interquartile ratios (0.34 / 0.36 / 0.33) and 95% limits of agreement (±55% / ±60% / ±50%). From median RC-time calculated from a random sample of 360 patients (derivation sample), the C value estimated in the remaining 359 patients (C = RC-time/PVR; validation sample) predicted the actual SV/PP ratio with high accuracy (bias = 2 %) but with low precision (SD of the bias = 29%) and wide 95% limits of agreement (from -50% +54%).
Conclusions: In idiopathic PAH, PA stiffness was related to the prevailing mPAP and was increased in high-risk groups whereas age and sex did not contribute. We documented for the first time a high degree of dispersion of RC-time that was essentially similar to the dispersion seen in patient’s age and mPAP. Furthermore, PA stiffness could not be estimated on the basis of PVR alone. This challenged the widely accepted current paradigm of RC-time constancy. Our results deserve further independent confirmation.