Conduit Artery Constriction Mediated by Low FlowA Novel Noninvasive Method for the Assessment of Vascular Function
Tommaso Gori, MD, PhD*, ,*,
Saverio Dragoni, MD*,
Monica Lisi, MD*,
Giuseppe Di Stolfo, MD*,
Serena Sonnati, MD*,
Massimo Fineschi, MD* and
John D. Parker, MD
* Department of Internal, Cardiovascular and Geriatric Medicine, University of Siena, Siena, Italy
Division of Cardiology, Department of Medicine, Mount Sinai and University Health Network Hospitals, University of Toronto, Toronto, Ontario, Canada.
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Figure 1 Representative Plot of FMD and Low-FMC
Radial artery diameter changes throughout the study of low–flow-mediated constriction (FMC) and flow-mediated dilation (FMD). After 1 min of resting radial artery diameter measurement, the wrist cuff is inflated (arrowhead) to suprasystolic pressure. At this point, the radial artery diameter progressively decreases in healthy volunteers until it reaches a plateau (low-FMC) at approximately 3' 30" after wrist cuff inflation and does not further constrict for longer occlusion times. Upon wrist cuff deflation (double arrowhead), the increased shear stress causes radial artery dilation (FMD). Therefore, L-FMC is a negative number, while FMD is a positive one. Doppler blood flows are reported at each time point. Image from the analysis software (4).
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Figure 2 Repeatability of FMD and L-FMC
Correlation analysis across consecutive (24 h) measurements of L-FMC (A) and FMD (B). The intraclass correlation coefficient (ICC) was higher for L-FMC. Abbreviations as in Figure 1.
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Figure 3 Bland-Altman Plots for Consecutive Measurements of L-FMC and FMD
The plots show a higher concordance for L-FMC (left) measurements. The dotted lines represent ± 1.96 SD. Abbreviations as in Figure 1.
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Figure 4 Mechanistic Hypothesis
(Left) Low–flow-mediated constriction (FMC) and FMD measurements during infusion of normal saline or levo-N-monomethyl arginine (L-NMMA) (8 µmol/min). Low–FMC was not modified by L-NMMA, suggesting that nitric oxide plays a lesser role in regulating resting arterial tone. *p < 0.01. (Right) Low-FMC and FMD measurements after placebo, fluconazole (150 mg orally), and aspirin (500 mg orally). Low–FMC was significantly blunted after fluconazole and aspirin. *p < 0.05. Abbreviations as in Figure 1.
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Figure 5 L-FMC, FMD, and the Composite End Point in Health and Disease
All 3 end points are blunted in the setting of cardiovascular disease. CAD = coronary artery disease; Htn = hypertension; other abbreviations as in Figure 1.
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