title: Measuring FMD in the brachial artery: how important is QRS gating?
abstract: Recommendations for the measurement of brachial flow-mediated dilation (FMD) typically suggest images be obtained at identical times in the cardiac cycle, usually end diastole (QRS complex onset). This recommendation presumes that inter-individual differences in arterial compliance are minimized. However, published evidence is conflicting. Furthermore, ECG gating is not available on many ultrasound systems; it requires an expensive software upgrade or increased image processing time. We tested whether analysis of images acquired with QRS gating or with the more simplified method of image averaging would yield similar results. We analyzed FMD and nitroglycerin-mediated dilation (NMD) in 29 adults with type 2 diabetes mellitus and in 31 older adults and 12 young adults without diabetes, yielding a range of brachial artery distensibility. FMD and NMD were measured using recommended QRS-gated brachial artery diameter measurements and, alternatively, the average brachial diameters over the entire R-R interval. We found strong agreement between both methods for FMD and NMD (intraclass correlation coefficients = 0.88-0.99). Measuring FMD and NMD using average diameter measurements significantly reduced post-image-processing time (658.9 ± 71.6 vs. 1,024.1 ± 167.6 s for QRS-gated analysis, P < 0.001). FMD and NMD measurements based on average diameter measurements can be performed without reducing accuracy. This finding may allow for simplification of FMD measurement and aid in the development of FMD as a potentially useful clinical tool.
authors.affiliation: Cardiovascular Medicine Division, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
authors.forename: Tinoy J
authors.initials: TJ
authors.lastname: Kizhakekuttu
authors.forename: David D
authors.initials: DD
authors.lastname: Gutterman
authors.forename: Shane A
authors.initials: SA
authors.lastname: Phillips
authors.forename: Jason W
authors.initials: JW
authors.lastname: Jurva
authors.forename: Emily I L
authors.initials: EI
authors.lastname: Arthur
authors.forename: Emon
authors.initials: E
authors.lastname: Das
authors.forename: Michael E
authors.initials: ME
authors.lastname: Widlansky
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D001794:Blood Pressure; D001916:Brachial Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016022:Case-Control Studies; D003187:Compliance; D003924:Diabetes Mellitus, Type 2 / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003971:Diastole; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D006940:Hyperemia / Q000000981:diagnostic imaging / Q000503:physiopathology; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D005996:Nitroglycerin; D015588:Observer Variation; D011237:Predictive Value of Tests; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D014463:Ultrasonography; D014664:Vasodilation; D014665:Vasodilator Agents; D055815:Young Adult
chemical_list: D014665:Vasodilator Agents; D005996:Nitroglycerin