Objective ·To analyze the progression of children with severe coronary artery lesions due to Kawasaki disease by coronary artery angiography, and evaluate the diagnostic value of echocardiography in these children. Methods ·A retrospective analysis was performed to enroll children with Kawasaki disease whose coronary artery lesions were graded Ⅳ or above from Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, from January 2013 to January 2023. The subjects were required to have received at least 2 times of coronary angiogram, and their clinical and imaging data were collected to analyze the progression of the lesions. Echocardiography results were compared with the results of the coronary angiogram. Results ·A total of 21 children were included, including 15 males and 6 females, with a median age at onset of 3 years and 6 months, a median age at initial coronary angiography of 7 years and 11 months, a median interval of 4 years and 5 months between the time of onset and initial angiography, a median age at angiographic review of 9 years and 2 months, and a median interval of 1 year and 3 months between the time of initial angiography and review. Coronary stenosis or occlusion was detected in 13 children in the initial angiography, of whom 6 underwent coronary artery bypass grafting (CABG) and had their angiography reviews 1 year later. The review results showed that the bridging vessels were unobstructed and no obvious stenosis was observed. Fifteen children had progression of the lesions detected by echocardiography in the subsequent follow-up and had their angiogram reviews, of whom 8 had significant progression of the coronary lesions. Intracoronary balloon dilatation was performed in 1 case, and CABG was performed in another case. Sixteen lesions of coronary stenosis or occlusion were detected in the initial angiography in 21 children, while only 1 lesion of coronary stenosis was detected by echocardiography during the same period of time. Twenty-eight medium- to large-sized coronary aneurysms were detected in the initial angiography in the 21 children, and the diameters of the 28 aneurysms measured by echocardiography and coronary angiogram were subjected to the Bland-Altman analysis. The Bland-Altman analysis showed that the difference in maximum diameter between 2 methods was (1.63±2.33) mm, with 95%CI of -2.95?6.21 mm. Conclusion ·Coronary artery lesions due to Kawasaki disease may be progressive; in the children with severe lesions, coronary artery stenosis or occlusion may be missed or misdiagnosed and some errors may exist in the measurement of diameters of aneurysms by echocardiography. Regular review of coronary angiography is needed.