Assessment of flow-mediated dilation (FMD)

Endothelial function will be measured noninvasively by using brachial artery ultrasound (EnVisor series, Philips Ultrasound, Bothell, WA, USA). This assessment will be performed with a 7 to 12 MHz linear transducer in a heated room at 21 to 24 °C at ICFUC. A software program will be used for two-dimensional color-Doppler imaging acquisition with a simultaneously recorded electrocardiogram (ECG). Image data will be recorded on a DVD. To minimize operational errors, the subject’s arm, and the ultrasound transducer will be positioned and maintained in the same position during the procedure. Baseline images will be recorded. A cuff will be placed around the forearm and inflated to 50 mmHg above systolic pressure for at least 5 min and then removed. Longitudinal ultrasound images of the brachial artery walls will be acquired to assess endothelium-dependent vasodilation. The expected coefficient of variation between the images will be 1.8 to 5.0 %. Flow-dependent vasodilation responses will be expressed as the percentage change in the brachial diameter [36].