Cardiac muscle is a muscle tissue composed of cardiac myocytes. The broad definition of cardiac myocytes includes the specially differentiated cardiac myocytes that make up the sinoatrial node, intraatrial bundle, atrioventricular junction, atrioventricular bundle (i.e., Heath bundle), and Purkinje fibers, as well as the general working cells of the atrial and ventricular myocardium. The first five species make up the pacing and conduction system of the heart, and they contain few or no myogenic fibers, so none of them has a contractile function; however, they are autoregulatory and conductive and are the functional basis for the autoregulatory activity of the heart; the latter two species are contractile and are the functional basis for the diastolic activity of the heart. Myocardial dystrophy is usually caused by cardiomyopathy, a disease that is very difficult to diagnose, relying mainly on symptoms and physical examination. Characteristic abnormalities can sometimes be demonstrated on the electrocardiogram. Echocardiography and magnetic resonance can be used to confirm the diagnosis of the disease. If the diagnosis is still not confirmed, cardiac catheterization may be performed. Endomyocardial biopsy can also be performed during catheterization to obtain a definite diagnosis and clarify the cause. 1, ECG examination dilated cardiomyopathy: ECG 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, some Q waves, atrioventricular block and bundle branch conduction block are also more 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 of hypertrophic cardiomyopathy: physical examination of the heart boundary can be enlarged to the left, the precordial region can be heard in systole, late jet murmur, the second heart sound is often split. Restrictive cardiomyopathy: The heart beat is weak, the heart sound is pure, the second heart sound in the pulmonary valve area is hyperactive, and the diastolic gallop rhythm and arrhythmia can be heard. Dilated cardiomyopathy: the heart chambers are enlarged, the septum, the posterior wall of the left ventricle is weakened, the ejection fraction is reduced, and the left and right ventricular outflow tracts 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 the 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 show a mildly enlarged heart with some visible endocardial calcification shadows.