Source: Sepehrvand N, James SK, Stub D, Khoshnood A, Ezekowitz JA, Hofmann R. Effects of supplemental oxygen therapy in patients with suspected acute myocardial infarction: a meta-analysis of randomised clinical trials. Heart. 2018;104:1691-1698.
Study Population: Roughly 8000 subjects experiencing a heart attack
Efficacy Endpoints: Mortality, subsequent heart failure
Harm Endpoints: Not assessed
Narrative: Myocardial infarction (MI), or heart attack, is the death or injury of heart muscle when blood flow is abruptly cut off, and is a leading cause of death internationally with approximately 1.5 million cases per year in the United States.1 Supplemental oxygen in patients with MI (regardless of baseline oxygen level) is often used to improve oxygen supply to heart muscle, in hopes of reducing cardiac damage and thus improving outcomes.2, 3, 4
The systematic review discussed here, including nearly 8000 subjects from 8 randomized trials,5 is dominated by a single nationwide registry trial of 6629 subjects in Sweden.6 In this study, patients with suspected myocardial infarction (based on either ischemic electrocardiographic or blood troponin changes) and normal oxygen saturation were randomly assigned to receive either supplemental oxygen by face mask for 6-12 hours or ambient air, in a non-blinded fashion.6 Oxygen therapy did not reduce death or any other endpoint measured at 2.1 years, and no subgroups were differentially benefited or harmed.6 These findings echoed the systematic review.5
Caveats: The main limitation of these data is inherent to the design of large registry trials like the Swedish one reported here. Registry trials are often pragmatic, eschewing steps such as blinding, and other features designed to minimize variation and bias. However, such trials have the advantage of being performed in ways that are consistent with usual practice, suggesting their results will translate more easily when implemented. The investigators in the Swedish trial did attempt to limit biases by, for instance, blinding outcome assessors to group assignments, and it is reassuring that the findings of 7 other trials included with in the systematic review5 are consistent with this large study. However, it remains feasible that methodologically more rigorous studies could find small outcome differences not detected in these data.
In conclusion, existing evidence does not support routine supplemental oxygen for patients with acute myocardial infarction. Therefore, we have assigned a color recommendation of Red (No Benefit) to this intervention.
Author: Jia Jian Li, MDSupervising editors: Shahriar Zehtabchi, MD
Published/Updated: February 1, 2019
The title bar is color-coded with our overall recommendation.