Pulmonary arterial stiffness: Toward a predictor of PAH and a key parameter to make PH reversible

© 2016 by Nova Science Publishers, Inc. Right ventricular (RV) adaptation to increased pulmonary arterial (PA) load is a critical determinant of outcomes in pulmonary hypertension (PH). Pulmonary vascular resistance (PVR) and total pulmonary vascular capacitance (Cp) assess global resistive and elastic properties of the pulmonary arterial vasculature, respectively. They show an inverse relationship that is usually described by a hyperbolic fit in both health and disease states including arterial PH (PAH). Conflicting data is supporting PVR to be prognostic value in PH. However, Cp is a strong independent predictor of mortality in patients with PAH. Cp depends on the prevailing mean pulmonary arterial pressure (mPAP) and on a genuine change in the arterial wall stiffness as a result of vascular remodeling. At present, we lack a complete understanding of the process of large/proximal and small/distal PA stiffening during the course of PH disease. Current dogma suggests that distal changes in the pulmonary vasculature usually precede those associated with stiffening in the central vessels. However, recent data have provided evidence that conduit systemic arterial stiffness is an independent predictor of blood pressure progression and incident hypertension. Similarly, data in pulmonary circulation suggests that vascular stiffening itself may be the initial vascular event that begets subsequently remodeling. Accordingly, human data seem to indicate that pulmonary intimal lesions are associated with the severely increased mPAP in the late stage of the disease. Recent evidence shows that large PA stiffening impairs its buffering function and increases distal vasculature flow pulsatility leading to distal PA remodeling and stiffening. Although PAH remains an incurable disease, animal models of PH and emerging human data put on doubt the concept of the pulmonary vascular remodeling irreversibility and emphasize efforts that experts must make for early detection of pulmonary vascular disease. We will address the PVR-Cp product of the pulmonary circulation as a global estimate of RV afterload, the assessment of the local arterial stiffness indices and its relationship with PVR and Cp, and finally, we put forward the cause-effect relationships between large/conduit stiffening and distal/resistive vascular disease, analyzing if it is possible the reversible remodeling in PAH.