Age‐related differences in blood pressure, ultrasound‐derived arterial diameters and arterial wall stiffness parameters in horses

Background Arterial rupture mainly affects older horses. The reason why older horses are more prone to arterial rupture and which underlying vascular changes predispose older horses to aortic rupture is still unclear. Objectives To investigate the effect of ageing on the equine arterial wall and blood pressure. Study design Cohort study. Methods Non‐invasive blood pressure measurement using a tail cuff and vascular ultrasound from aorta, common carotid artery and external iliac artery was performed in 50 healthy young (3‐7 years) and 50 healthy old Warmblood horses (>18 years). Arterial diameters and cross‐sectional areas, and arterial wall thickness were measured offline. Regional arterial wall stiffness of the aorta and common carotid artery were assessed using pulse wave velocity, while lumen area/diameter change, strain, compliance and distensibility were calculated to assess local arterial wall stiffness. Results No difference in blood pressure was found between old and young horses. All arterial dimensions and intima‐media thickness of the common carotid artery were significantly larger in old horses. A significantly higher local arterial wall stiffness was found for the aorta and the caudal common carotid artery in older horses. For the external iliac artery, no significant differences in arterial wall stiffness were found. Both aortic and carotid pulse wave velocities were higher in older horses compared with younger horses. Main limitations Blood pressure was measured non‐invasively. Conclusions In horses, arteries stiffen with age, in combination with luminal enlargement and arterial wall thickening. This might, at least partially, explain the increased incidence of arterial rupture in older horses.