The normal range of lactate dehydrogenase does not exceed 300 U/L. If the value of lactate dehydrogenase reaches 500 U/L, there is already a more obvious elevation, and it is necessary to determine the specific cause of lactate dehydrogenase elevation by combining clinical symptoms, signs and relevant auxiliary examinations. Since lactate dehydrogenase is mainly found in the heart muscle, skeletal muscle, kidney, liver and other tissues and organs, when lactate dehydrogenase is significantly elevated in clinical practice, lesions in these tissues or organs should also be considered first. Diseases that cause increased lactate dehydrogenase in clinical practice include Creutzfeldt-Jakob disease, viral myocarditis, acute myocardial infarction, acute and chronic hepatitis from various causes, liver cirrhosis, hemolytic anemia, myotonic dystrophy, pulmonary infarction, acute tubular necrosis, chronic pyelonephritis, glomerulonephritis, and so on. In this case, further lactate dehydrogenase isoenzyme assay can be performed to further clarify whether the elevated lactate dehydrogenase is caused by cardiomyopathy.