COX7A2L and myocardial infarction: However, when the heart was kept at 37 °C for 1 h in the absence of oxygen to simulate ischemia during myocardial infarction, levels of COX7AR present in the purified COX complex were significantly increased (Fig. 2e), suggesting that increased incorporation of COX7AR in the COX enzyme complex is driven by ischemic stress.