Earliest light microscopic change in myocardial infarction is:

When there is depletion of ATP, there is development of swelling in Myofibers leading to the haphazard arrangement of fibres causing waviness of the fibers. The typical changes of coagulative necrosis become detectable in the first 6 to 12 hours. "Wavy Fibers" may be present at the periphery of the infarct. These changes probably result from the forceful systolic tugs of the ble fibers on immediately adjacent, noncontractile dead fibers, causing stretching and folding.