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Assessment of brachial vasodilation: Flow-mediated vasodilation is assessed on the brachial artery by ultrasound. Measurements are performed in the supine position on the non-dominant arm after 10-20 minutes of resting in a quiet, dark room with a temperature of 22°C. The brachial artery is scanned longitudinally just above the antecubital crease using a linear multifrequency 5-12-MHz transducer. Brachial artery diameter is measured at the R wave of the electrocardiogram, on the interface between the media and adventitia of the anterior and posterior wall. Hyperemia is induced by infl ation of a pneumatic cuff (12.5 cm wide) at 230-250 mm Hg for 4 minutes on the most proximal portion of the forearm. Arterial diameter measurement is repeated 45-60 seconds after sudden deflation of the cuff. Tracings are recorded on videotape. The average of 3 measurements of basal and post-hyperemia diameter are used for the analysis. At least 10 minutes of rest after reactive hyperemia, spray nitroglycerin (0.4 mg) is administered to assess nitrate-mediated vasodilation. The brachial artery diameter is measured before and 4 minutes after drug administration. Flowmediated and nitrate-mediated vasodilation are expressed as the relative increase in brachial artery diameter during hyperemia or nitrate administration.