Figure 1. Myocardial cells require continues oxygen supply in order to maintain normal metabolism. If oxygen supply is less than oxygen demand, ischemia developes. Myocardial cells can switch to anaerobic metabolism and discontinue contractions in order to alleviate the ischemia. This enables the cell to endure up to 30 minutes of severe ischemia. If blood flow is not restored before 30 minutes, the cell will die. Death of myocardial cells is referred to as myocardial infarction.