(i) Applications in valvular disease: mitral stenosis, aortic stenosis, tricuspid stenosis, mitral regurgitation, aortic regurgitation, tricuspid regurgitation, evaluation of prosthetic valves. (ii) Application in case of infective endocarditis: Two-dimensional echocardiography can show each valve of the heart, thus further improving the detection rate of intracardiac bulges. (iii) Application in congenital heart disease: atrial septal defect, ventricular septal defect, endocardial cushion defect, patent ductus arteriosus, aortic sinus aneurysm rupture, coronary artery fistula, triple atrium heart, right ventricular double outlet, pulmonary orifice stenosis, aortic orifice stenosis, aortic constriction, tetralogy of Fallot, transposition of the great arteries, permanent arterial trunk, single ventricle, tricuspid atresia, Ebstein’s malformation, complete pulmonary vein malformation drainage. (iv) In coronary heart disease: myocardial ischemia, myocardial infarction, complications of myocardial infarction (ventricular wall aneurysm, appendage thrombosis, septal rupture, papillary muscle insufficiency) (v) In cardiomyopathy: dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy.