The most important cardiac ultrasound index of Kawasaki disease is to focus on whether there is any lesion in the coronary artery. The so-called coronary artery lesions are as follows: First, to see if the coronary artery is dilated. For children under 5 years of age, the coronary artery is generally less than 3 mm, which is considered normal, but if the inner diameter of the coronary artery is greater than 3 mm, it is considered dilated. For children over 5 years old, the internal diameter of the coronary artery should not be larger than 4 mm, but if it is larger than 4 mm, the coronary artery is also considered dilated. Second, to see if there is any coronary artery aneurysm formation, the so-called coronary artery aneurysm can be seen by echocardiography as a significant aneurysmal dilatation in the left and right coronary arteries or one of them. The so-called aneurysm-like dilatation means that the inner diameter of the aneurysm is greater than 2-3 times the inner diameter of the front branch or trunk, then it is considered to have an aneurysm. Thirdly, to see if there is any change in the left ventricular ejection fraction of cardiac function and whether the internal diameter of the heart is normal. Fourth, see if there is any pericardial effusion, because some children with Kawasaki disease may have transient pericardial effusion. These are some of the main indicators of Kawasaki disease that are observed on cardiac ultrasound.