This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Conducting System of Hea, Subject name: Physiology
The basic reason for "reperfusion injury" to the myocardium is: 
Select and explain. 
A. Generation of free radicals, B. Extension of the ischemic zone, C. Increased ICF, D. Increased ECF
C: Increased ICF
Answer: C: Increased ICF 
Explanation: 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".