The basic reason for "reperfusion injury" to the myocardium is:
After MI, there is failure of Na+-K+ pump resulting in NCX failure Thus intracellular Ca+2 increases Now when perfusion is established (nutrients are available), because of increased ICF Ca+2, cardiac fibers contract very strongly Already muscle fibers are fragile due to M.I, now this contraction results in fuher damage. This is basic reason for "reperfusion injury".
Generation of free radicals
Extension of the ischemic zone
Increased ICF
Increased ECF
Conducting System of Hea