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
[{'content': 'The basic reason for "reperfusion injury" to the myocardium is: \nSelect and explain. \nA. Generation of free radicals, B. Extension of the ischemic zone, C. Increased ICF, D. Increased ECF', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 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".', 'role': 'assistant'}]