2.4. Assessment of brachial artery endothelial function
To evaluate the endothelial function of the brachial
artery noninvasively, flow-mediated endothelium-dependent vasodilation
was assessed by measuring the brachial artery diameter at baseline and
during reactive hyperemia. All patient fasted for at least 8 h and
avoided consuming caffeine or smoking cigarettes for 12 h prior to their
vascular examination. All vasoactive medications were withheld 8 hours
before the scan. Each patient were rested in a supine position for 30
min and remained in a quiet, air-conditioned room, with its temperature
kept between 20 and 22 ◦C. All studies were performed using an
ultrasound system (Philips EPIQ 7C, Philips Healthcare, Andover, MA,
USA) with a broadband linear array transducer with a 3-12 MHz range
(Philips L12-3). The brachial artery was viewed longitudinally 5 cm
above antecubital fossa and FMD was assessed according to the existing
guidelines(10).
When the clearest image of the anterior and posterior intimal interfaces
between the lumen and vessel wall was obtained, baseline diameter
measurements were taken at the end of the diastole (timed by the peak of
R wave on electrocardiogram) for ≥ 3 times. Before starting measurement,
cuff was fitted distally to the brachial artery. After baseline
measurement, the cuff was inflated to at least 50 mm Hg above systolic
pressure to occlude arterial inflow for 5 minutes. The longitudinal
image or artery was scanned continuously from 30 s before to 90 seconds
after cuff deflation and the maximal diameter of the artery was defined
during reactive hyperemia. The basal diameter was defined as the average
of all measures collected before inflation, and FMD was calculated as
the percentage change in peak vessel diameter from the baseline value
following cuff deflation: peak diameter−baseline diameter) / baseline
diameter. In present study, according to the results of previous
studies, FMD value under 10.0% was accepted as endothelial dysfunction
(11,12).