Feasibility of echocardiographic estimation of Pulmonary Artery Stiffness in horses

Pulmonary artery stiffness (PAS) is an index of pulmonary artery elasticity that permits to evaluate the pulmonary vascular bed in humans. It can early detect an increase in pulmonary artery stiffness as a consequence of remodeling of the vessel wall caused by chronic pulmonary and congenital heart diseases. This remodeling can occur also in horses with chronic respiratory diseases. Thus, PAS could be a useful echocardiographic parameter also in horses. However, in literature, there are no studies regarding PAS in horses. The aim of this study is to evaluate the feasibility of PAS in horses. Fifteen healthy horses were included in this prospective study. Maximal frequency shift (MFS) and acceleration time (AT) were measured from the pulsed-wave Doppler trace of the pulmonary artery flow, obtained from the right parasternal short-axis view at the level of the pulmonary artery, and then PAS was calculated as the ratio of MFS to AT. The low variability assessed for intra- and inter-observer variability, day-to-day variability and image acquisition variability suggests that PAS can be measured consistently in horses. Further studies could be useful to assess the clinical usefulness of PAS in unhealthy horses, such as those affected by chronic respiratory diseases.