There are few methods to evaluate endothelial function. Quantitive coronary angiography is the most accurate method. In this method during angiography the coronary response to acetylcholine injection is evaluated . However this is an invasive method and not suitable for children. A second alternative, brachial artery ultrasound scanning, is a noninvasive method using Doppler to measure the brachial artery diameter before and after manometric cuff was inflated to supra-systolic pressure [6, 20].