Letter by Bulluck and Hausenloy Regarding Article, “Air Versus Oxygen in ST-Segment–Elevation Myocardial Infarction”

The use of high-flow oxygen in the setting of acute myocardial infarction remains controversial. We therefore read with great interest the randomized, controlled clinical trial by Stub et al, 1 which investigated the effect of supplementary oxygen versus air in normoxic patients presenting with an acute ST-segment-elevation myocardial infarction. In their study, the authors concluded that supplementary oxygen therapy may increase early myocardial injury and is associated with larger myocardial infarct size assessed by cardiovascular magnetic resonance at 6 months in patients who have ST-segment-elevation myocardial infarction. However, the data provided in the study do not appear to support this conclusion. First, it was based on a difference in peak levels of serum creatine kinase between the 2 groups. However, creatine kinase is known to be less specific for myocardial necrosis, 2 and the study had not been originally powered to detect this end point. The authors had actually powered the study based on peak levels of serum troponin I, a more specific biomarker for myocardial necrosis than creatine kinase, and for which there was no significant difference between the 2 groups. Second, they reported a difference in myocardial infarct size at 6 months in grams measured by cardiovascular magnetic resonance, but when this was normalized to left ventricular mass, there was no significant difference between the 2 groups. In the absence of T2-weighted cardiovascular magnetic resonance imaging to quantify the area-at-risk, the authors could have used coronary angiographic jeopardy scores to estimate the area-at-risk and calculate myocardial salvage, In summary, the data do not appear to support the conclusion that supplemental oxygen may be harmful in normoxic patients who have ST-segment-elevation myocardial infarction in comparison with air-rather, it shows no added benefit with this therapeutic approach.