In Reply We appreciate Thijssen and Green’s interest in our article.1 We agree that the accurate measurement of flow-mediated vasodilation (FMD) requires training and standardization and that adherence to expert-consensus guidelines is important, as it lowers measurement variation in FMD studies. Our study did adhere to the guidelines from the International Brachial Artery Reactivity Task Force,2 which were the accepted guidelines at the time we acquired the data. Following these guidelines, and as described in the article,1 we used strict pretest patient preparation. Participants were tested in the morning after a 12-hour fast. They rested supine for at least 20 minutes in a quiet, darkened, temperature-controlled room. Longitudinal B-mode ultrasonography images of the right brachial artery were obtained and images were digitalized. The arterial diameter was measured using an edge-detection software (Medical Imaging Applications) by an experienced ultrasonography technician. In our analysis, we adjusted for baseline diameter and shear stress, and all measurements (baseline brachial artery diameter, absolute and relative FMD response, allometrically scaled FMD, and hyperemic velocity-time integral) were provided in the Supplement.1 We have performed FMD research for 3 decades, and our technicians undergo rigorous training to ensure the high interoperator and intraoperator reliability of our laboratory. Our protocol was identical to the protocol recommended by the recent expert opinion reports by Thijssen et al,3,4 except that we did not perform continuous assessment of arterial diameter but assessed the peak diameter responses at 60 seconds and 90 seconds postdeflation.2 The peak diameter on average was greater at 60 seconds than at 90 seconds, and thus, we have presented the 60-second data in our article.1
Lima BB, Quyyumi AA, Vaccarino V. A Future for Flow-Mediated Dilation—Just Follow the Guidelines—Reply. JAMA Cardiol. 2020;5(3):361. doi:10.1001/jamacardio.2019.5701
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