Currently, research on the effect of thiamine administration during transcatheter closure on the structure and function of the left ventricle by examining levels of matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 in children with left to right shunt congenital heart disease has never been carried out in Indonesia, so it is necessary carried out this research. This research was carried out by administering 100 mg of thiamine once per day to patients post transcatheter closure for 28 days. The parameters assessed were MMP-9, TIMP-1, and echocardiography to assess the structure and function of the left ventricle in CHD patients with left to right shunt lesions.