Because LDH is present in so many types of cells, high levels of LDH may indicate any one of a number of conditions. Elevated levels of LDH isoenzymes may indicate: 1  blood flow deficiency. 2  cerebrovascular accident, such as a stroke. 3  certain cancers. 4  heart attack. 5  hemolytic anemia. 6  infectious mononucleosis. 7  liver disease, such as hepatitis.