Irreversible injury in myocardium occurs at: (A) 2 minutes, (B) 30 minutes, (C) 2 hours, (D) 5 hours
Answer is B. Only severe ischemia lasting at least 20 to 40 minutes causes irreversible damage and myocyte death leading to coagulation necrosis. Withlonger periods of ischemia, vessel injury ensues, leading to microvascular thrombosis.( Robbins Basic Pathology, 9th edition, page 377 )