Reproducibility of arterial diameter measurements using B‐ and M‐mode ultrasonography in standing Warmblood horses

Abstract

Background: In human medicine, arterial wall stiffness (AWS) parameters are calculated from ultrasonographically measured diastolic (DD) and systolic arterial diameter (SD) in order to assess vascular health. In horses, information regarding reproducibility of ultrasonographic measurements of arterial diameters is lacking. Objectives: To evaluate the inter-day, inter-observer and intra-observer variability of ultrasonographic arterial diameter measurements in horses. Study Design: Prospective study. Methods: In ten healthy, adult Warmblood horses, ultrasound images were recorded on two different days from aorta (B-mode), common carotid and femoral artery (B-mode and M-mode). In addition, heart rate and non-invasive blood pressure were recorded simultaneously. From blinded data, DD and SD were measured over nine cardiac cycles from B/M-mode images of both days, and from each horse, one exam was measured again by the same observer and by a second, independent observer. Inter-day, inter-observer and intra-observer coefficients of variation were calculated. Carotid and femoral diameter measurements from M-mode were compared with diameters derived from measured areas on B-mode images using a paired t-test. Results: There was no significant difference in heart rate or blood pressure between both days. Mean B-mode DD and SD (±standard deviation) for aorta, carotid and femoral artery were 59.8±4.1mm and 66±4.4mm, 11.7±1.1mm and 12.3±1.2mm, and 12.8±1.1mm and 13.2±1.0mm, respectively. The latter were not significantly different from M-mode measurements. For DD and SD from M and B-mode images of all three arteries, inter-day (4-9%), inter-observer (1-3%) and intra-observer (1-2%) variability was low. Main Limitations: A larger group of healthy horses must be examined to define reference ranges for arterial diameters. Conclusions: Our results show good reproducibility of aortic, carotid and femoral diameter measurements using both B- and M-mode ultrasonography, suggesting these are potentially useful variables for assessing AWS in horses.