Data from DET02X-AMI (Determination of the role of oxygen in suspected acute myocardial infarction) show that supplemental oxygen in normoxic patients with suspected myocardial infarction does not significantly improve outcomes compared with ambient air. A previous study, AVOID (Air versus oxygen in ST-segment elevation myocardial infarction) found that supplemental oxygen significantly increased myocardial injury in patients with ST-segment elevation myocardial infarction.
Speaking at the European Society of Cardiology (ESC) congress (26–30 August, Barcelona, Spain), Robin Hofmann (Karolinska Institutet, Department of Clinical Science and Education, Division of Cardiology, Södersjukhuset, Stockholm, Sweden) reported that the use of supplemental oxygen in normoxic patients with suspected myocardial infarction has become controversial. He explained that while supplemental oxygen has been “used for more than a century and is widely recommended by guidelines”, there is limited evidence to support its use in this setting and studies have actually suggested that it may be harmful. “This discussion was further fuelled by the AVOID trial, which showed larger infarcts with oxygen,” Hofmann added.
Given that previous studies of supplemental oxygen, such as AVOID, were relatively small, Hofmann and colleagues aimed to provide further evidence on the issue. DET02X-AMI, therefore, was designed as a registry-based randomised clinical trial. Through a national comprehensive quality registry of coronary care (ie. SWEDEHEART), they identified 6,629 normoxic patients with suspected myocardial infarction. Of these, 3,311 were assigned to receive oxygen and 3,318 were assigned to receive ambient air. Hofmann noted that the number of patients in the study meant that DET02X-AMI was “more than six times the size” of the previous studies combined. The primary endpoint was the one-year rate of all-cause death.
At one year, there were no significant differences—in the intention-to-treat population—between the two groups in the rate of the primary endpoint: 5% for oxygen vs. 5.1% for ambient air (p=0.8). This finding was consistent across all pre-specified subgroups. Additionally, there were no significant differences between groups in the rate of rehospitalisation for myocardial infarction (at one year) or in the 30-day composite rate of death and rehospitalisation for myocardial infarction. Furthermore, according to Hofmann, when measured by highly sensitive Troponin T, the extend of myocardial injury in the oxygen and ambient air group was “virtually identically”.
Concluding, he said: “In this pragmatic, registry-based randomised clinical trial evaluating supplemental oxygen vs. ambient air in patients presenting with suspected myocardial infarction who did not have hypoxaemia, we did not find a beneficial effect of oxygen treatment with respect to all-cause mortality at one year.”
Going forward, Hofmann told Cardiovascular news, the use of oxygen therapy should be guided by saturation levels. “With levels of 90% or above the patient with suspected acute myocardial infarction does not gain benefit of supplemental oxygen and, therefore, it should not be used. Thereby the caregiver wins both time to treat the patients with other more effective measures and saves money for the healthcare system,” he says.
Noting that, based on the findings of DETOX-AMI, European guidelines no longer recommended supplemental oxygen, Hofmann believes other guidelines should follow this example. He notes: “Soon, we will be able to provide more detailed info on other outcomes, but for the routine use in patients with suspected acute myocardial infarction, oxygen should not be recommended henceforth.”
The study was simultaneously published in The New England Journal of Medicine.