Objective—To compare flow-mediated vasodilation (FMD) measurements in brachial and femoral arteries of healthy dogs habituated to the assessment method, evaluate repeatability of these measurements, and investigate effects of blood pressure cuff inflation time on femoral artery FMD measurements.
Animals—11 healthy adult Miniature Schnauzers.
Procedures—Arterial luminal diameter and blood flow velocity integral (FVI) were measured before and after cuff inflation of 5 minutes' (brachial and femoral arteries) or 3 minutes' duration (femoral artery) in separate experiments. A blood pressure cuff was inflated to > 200 mm Hg distal to each imaging site to increase local blood flow to induce reactive hyperemia. Changes in FVI after cuff deflation, FMD, and between-dog and within-dog coefficients of variation (CVs) were determined.
Results—After cuff inflation of 5 minutes' duration, greater changes were detected in median change in FVI and FMD of brachial arteries (174.0% and 8.0%, respectively), compared with values determined for femoral arteries (32.0% and 2.1%, respectively). Between-dog CV for brachial artery FMD was 34.0%, compared with 89.6% for femoral arteries, and within-dog CV was 32.5% for brachial arteries versus 51.6% for femoral arteries after cuff inflation of 5 minutes' duration.
Conclusions and Clinical Relevance—In healthy Miniature Schnauzers, FMD was greater and more repeatable in brachial arteries than in femoral arteries. Reactive hyperemia was inconsistently induced in femoral arteries following 3- or 5-minute cuff inflation times. Brachial, but not femoral, artery FMD measurement is a potentially useful research technique for measurement of endothelial function in 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. (Am J Vet Res 2010;71:1154–1161)
Objective—To determine between-pony and within-pony variations and interobserver and intraobserver agreements of a technique for measurement of flow-mediated vasodilation (FMD) in healthy ponies.
Animals—6 healthy pony mares (weight range, 236 to 406 kg; body condition score range, 3/9 to 7/9; age range, 14 to 25 years).
Procedures—In each pony, the left median artery was occluded with a blood pressure cuff (inflated to > 300 mm Hg for 5 minutes). Two-dimensional ultrasonographic images of the artery were recorded for 30 seconds before cuff inflation and for 2 minutes after cuff deflation. Maximum luminal diameters of arteries were compared with their baseline diameters to calculate FMD (relative percentage increase in luminal size). Images were obtained from 6 ponies 1 time and from 1 pony 6 times. Independent analysis of images was performed by 2 investigators, 1 of whom analyzed images on 2 occasions.
Results—Mean ± SD FMD in 6 ponies (1 time) was 12.57 ± 4.28% and in 1 pony (6 times) was 7.30 ± 2.11%. Between-pony and within-pony coefficients of variation were 34.09% and 28.84%, respectively. Interobserver agreement was fair (intraclass correlation coefficient, 0.47); intraobserver agreement was poor (intraclass correlation coefficient, 0.30).
Conclusions and Clinical Relevance—FMD was identified and measured in ponies. Measurement of FMD is used to assess endothelial function in humans and has been investigated in dogs. Measurement of FMD in ponies appeared to be feasible and could be used to assess endothelial function (to determine predisposition for development of laminitis or cardiovascular diseases).