Ratio of LDH isozymes H4 and H3M as diagnostic index in suspected cases of myocardial infarction.

The isozyme profile of lactic dehydrogenase (LDH) is being studied in this laboratory, mainly for the diagnosis in the suspected cases of myocardial infarction (MI). The isozymes are separated by polyacrylamide gel electrophoresis and the quantitative assay of the isoenzymes is done by enzyme staining followed by scanning with the help of an automatic scanner. In normal cases, the ratio of the two isozymes H4 and H3M is approximately 0.5. In almost all cases of myocardial infarction the ratio becomes 1 or more and sometimes increases up to 2. In the suspected and potential cases of infarction the ratio tends to become more than 0.5 (usually 0.7) but remains lower than 1. Thus, the measurement of the ratio may be a very helpful diagnostic index in the suspected and potential cases and may also be used for prognostic purposes as well.