Clin Res Cardiol 108, Suppl 1, April 2019
Better assessment of flow-mediated dilation (FMD) by measuring real dilatory peak time
T. Herbrand1, H. V. Coester1, J. H. DeVries1, C. Heiss2, T. Heise1, M. Kelm3, R. Sansone3
1Profil Institut für Stoffwechselforschung GmbH, Neuss; 2Faculty of Health and Medical Sciences, University of Surrey, Surrey, Großbritannien; 3Klinik für Kardiologie, Pneumologie und Angiologie, Universitätsklinikum Düsseldorf, Düsseldorf;

Objective

Due to technical limitations, it was until recently not possible to measure ultrasound video sequences longer than a limited number of heart cycles for the measurement of flow-mediated vasodilation (FMD). Therefore, researchers had to settle for recording a few heart cycles at pre-defined time points to estimate vasodilation and calculate FMD. This likely limits FMD accuracy and reproducibility. With state-of-the-art technology, one can nowadays measure and analyze ultrasound sequences up to several minutes. We aimed to identify of the real dilatory peak during FMD measurements and to compare this to assessing dilation at predefined time points.

Methods

In this study, FMD was measured in healthy, middle-aged people early in the morning by ultrasound (12-MHz transducer; GE Logiq P7, GE Healthcare, Solingen, Germany). In a subset of patients, FMD was measured again 30 days later. FMD was performed by two certified physicians and evaluated by three trained FMD analysts using an automated analysis system (Brachial Analyzer 5, MIA LLC, Coralville, IA, USA). FMD values were compared at two pre-defined time points,  60s and 90s, and at the real peak time between 0 – 110 seconds during reactive hyperemia after cuff deflation, using ANOVA.

Results

FMD was measured in 100 subjects (mean ± SD age 56 ± 4.5 years, BMI 26.2 ± 3 kg/m2, blood pressure 127 ± 10 / 80 ± 7 mmHg and HbA1c 5.4 ± 0.3%) at baseline and in 25 people again 30 days later (Fig. 1). FMD showed lower dilation at time points 60s and 90s compared to real peak time (Least Square mean difference (95% CI) 60s vs. real ‑1.09% (-1.33 to -0.87); p<0.0001 and 90 vs. real -1.93 (-2.18 to -1.69); p<0.0001, Fig 2). The intra-subject variability after 30 days was lowest for real peak time compared to 60s and 90s (15% vs. 36% and 51%, respectively). 

Conclusion

This study demonstrates that measuring FMD using state-of-the-art ultrasound devices and analysis methods allows for assessment of the real dilatory peak time during hyperemia. Real peak time FMD measurement demonstrated significantly more dilation and superior reproducibility compared to measuring FMD at pre-defined time points.

Figure 1. Illustrative example of an FMD ultrasound video sequence over 100 seconds for the determination of the real dilatory peak, which in this case falls at 30 seconds

 

Figure 2. FMD results based on brachial artery diameter at pre-defined time points and at real dilatory peak

 

 
https://www.abstractserver.com/dgk2019/jt/abstracts//V1296.htm