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

OBJECTIVE: To evaluate the between- and within-dog repeatability of a flow-mediated vasodilation (FMD) measurement technique in healthy dogs. ANIMALS: 43 male and female dogs of various breeds (weight range, 6.9 to 31.7 kg; age range, 11 months to 11 years). PROCEDURES: 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. RESULTS: 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. CONCLUSIONS AND CLINICAL RELEVANCE: 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.