Oxygen therapy does not improve survival in patients with heart attack symptoms, according to late-breaking research presented at a hotline session and published simultaneously in the New England Journal of Medicine (https://doi.org/10.1056/NEJMoal1706222).
The DETO2X-AMI study questioned the current practice of routine oxygen therapy for all patients with suspected myocardial infarction (MI), said Dr Robin Hofmann (Karolinska Institutet at Södersjukhuset, Stockholm, Sweden) who presented the study at the meeting. This prospective, randomised, open label trial enrolled 6,229 patients with suspected heart attack from 35 hospitals across Sweden. Half of the patients were assigned to oxygen given through an open face mask and the other half to room air without a mask.
The study – using a registry-based randomised clinical trial protocol – was representative of real world practice and used national registries, including SWEDEHEART, for randomisation, case record forms and follow up.
The primary outcome, the mortality rate one year after randomisation, was not statistically different between the two groups (5.0% in the oxygen group versus 5.1% in the air group). Similarly, there was no significant difference between the two groups for secondary end points, including the risk of a new heart attack or cardiac muscle injury measured by biomarkers. Even in patients at high risk, such as smokers, older patients, patients with diabetes, or patients with previous heart disease, the mortality results were similar at one year.
European Society of Cardiology (ESC) guidelines on the treatment of patients with ST segment elevation myocardial infarction (STEMI) recommend oxygen (by mask or nasal prongs) for patients who are breathless, hypoxic, or have heart failure. They add that the systematic use of oxygen in patients without heart failure or dyspnoea “is at best uncertain”. ESC guidelines have gradually shifted towards more restrictive use of oxygen, said one of the study authors Professor Stefan James (Uppsala University, Uppsala, Sweden). “While the current recommendations were based on expert opinion only, we can now add substantial new data from our large clinical trial.”
It is thought that clinical practice and future guidelines will change as a result of this study. “Our findings do not support the routine use of oxygen therapy in all patients with symptoms of a heart attack. The general use of oxygen in these cases is still widespread in the world but can now be adjusted,” said Professor James.
It was thought that oxygen therapy might be harmful arose after the AVOID trial found a larger infarct size in patients receiving oxygen therapy. “Routine oxygen therapy seems unnecessary in this patient group, but fortunately our data do not give any indication of increased risk for the patients on oxygen” said Professor James. “So all of us who have generally used oxygen for decades can now rest assured.”
The DETO2X-AMI trial is the first large randomised trial of oxygen therapy in patients with suspected myocardial infarction which is large enough to reveal meaningful findings on mortality and morbidity. The study enrolled six times more patients than all previous randomised trials of this therapy combined and included a much broader range of patients to make the results relevant to everyday clinical practice.
Discussant Professor David Newby (University of Edinburgh), said the study showed an “indisputable outcome” and congratulated the investigators, saying “to have delivered this trial is fantastic”.
You can find all of our reports from the ESC 2017 here.