Evaluation of a flow-mediated vasodilation measurement technique in healthy dogs

To evaluate the between- and within-dog repeatability of a flow-mediated vasodilation (FMD) measurement technique in healthy dogs.

43 male and female dogs of various breeds (weight range, 6.9 to 31.7 kg; age range, 11 months to 11 years).

5 dogs were used to refine the technique; other dogs were classified as large (>15 kg) or small (≥15 kg) before use in the main study. In each dog, a brachial artery was occluded for 5 minutes by inflating a blood pressure cuff (applied pressure was more than 50 mm Hg greater than that required to occlude flow). Two-dimensional ultrasonographic images of the artery were recorded during a 30-second period prior to cuff inflation (baseline) and during a 3-minute period after cuff deflation by each of 2 sonographers. Relative percentage increases in luminal size from baseline (ie, FMD) were calculated. Independent contributing factors to FMD (eg, body weight, age, and room temperature) were assessed.

Median FMD was significantly greater in small dogs (77%; range, 0% to 19.3%) than it was in large dogs (2.2%; range, -2.2% to 10.6%); values were significantly greater in dogs<6 years old, compared with dogs>6 years old. Weight was the only independent contributing factor for FMD. Coefficients of variation for between- and within-dog repeatability were 99.7% and 62.8%, respectively.

Application of the FMD measurement technique used in humans appears to be feasible in dogs and may provide a means of assessing canine endothelial function, although between and within-dog variations were large.