<prompt> The predominant isozyme of LDH in cardiac muscle isLD-1LD-2LD-3LD-5  <response>: In myocardial infarction, total LDH activity is increased, while H4 iso-enzyme monomer of LDH is increased 5-10 times more. The magnitude of the peak value, as well as the area under the graph, will be roughly propoional to the size of the myocardial infarct. Ref: D M Vasudevan 7th edition Page no: 304 