Due to the extensive ischemia, degeneration, necrosis and fibrosis of myocardium caused by multiple lesions of coronary arteries or even diffuse lesions, the blood supply of myocardium is insufficient for a long time, and the myocardial tissue becomes nutritionally impaired and atrophied, and necrosis leads to the proliferation of fibrous tissue, which can lead to ischemic cardiomyopathy. (1) Electrocardiographic examination: The electrocardiographic examination is dominated by ST-segment depression, T-wave depression or inversion, and a few appear pathological Q waves. Hypertrophic cardiomyopathy: ECG often shows left ventricular hypertrophy and ST-T changes, and some of them have Q waves, and atrioventricular block and bundle branch block are also common. Restrictive cardiomyopathy: ECG shows low voltage, atrial and ventricular hypertrophy, bundle branch block, ST-T changes and atrial fibrillation and other arrhythmias. (2) Physical examination: On physical examination, the cardiac border may be enlarged to the left, mid-systolic and late ejection murmurs may be heard in the precordial region, and the second heart sound is often split. Restrictive cardiomyopathy: The heart beat is weak, the heart sounds are pure, the second heart sound in the pulmonary valve area is hyperactive, and diastolic gallop rhythm and arrhythmia can be heard. (3) Echocardiography: The heart chambers are enlarged, the septum and posterior wall of the left ventricle are weakened, the ejection fraction is reduced, and the outflow tracts of the right and left ventricles are enlarged. Hypertrophic cardiomyopathy: Echocardiography is of great diagnostic value for this disease, showing hypertrophy of the septum and left ventricular wall, the ratio of the two thicknesses is more than normal 1.3:1, clinical manifestations, combined with echocardiography and ventriculography can often confirm the diagnosis. Restrictive cardiomyopathy: 2D echocardiography shows narrow chambers, apical occlusion, endocardial thickening and severely impaired ventricular diastolic function. (4) Others: Ventriculography may show a narrowed ventricular cavity with hypertrophic myocardium protruding into the ventricular cavity in hypertrophic cardiomyopathy. In dilated cardiomyopathy, X-rays may reveal a mildly enlarged heart, with some endocardial calcification shadows.