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Oxygen therapy after heart attack does not prevent heart failure

Researchers say their findings indicate that routine use of oxygen is unnecessary and should be stopped

Ingrid Torjesen

Tuesday, 28 August 2018

Oxygen therapy does not prevent the development of heart failure and does not reduce the long-term risk of dying for patients with suspected heart attack, a major Swedish study* has shown for the first time.

Oxygen has been used to treat patients suffering a heart attack for more than a century, despite the fact that such treatment has not had any scientifically proven effect on patients who have normal oxygen levels in their blood. Since the turn of the millennium, researchers worldwide have started to question whether oxygen therapy for heart attacks is ineffective - or may even be harmful.

In the DETO2X-AMI study conducted at 35 Swedish hospitals, 6,629 patients with suspected heart attack and oxygen saturation of ≥90% were randomly assigned to receive either supplemental oxygen at 6 L/min for six to 12 hours delivered by open face mask or ambient air.

The result presented at the European Society of Cardiology's (ESC) cardiology congress in Munich and published in the journal Circulation shows that oxygen therapy in a moderate dose is not harmful but that it does not increase the survival rates or reduce complications, such as the development of heart failure or new heart attacks.

Acute heart failure treatment, left ventricular systolic function assessed by echocardiography, and infarct size measured by high-sensitive cardiac troponin T were similar in the two groups during the hospitalization period. All-cause death or hospitalization for heart failure within one year after randomization occurred in 8.0% of patients assigned to oxygen and in 7.9% of patients assigned to ambient air (hazard ratio, 0.99; 95% CI, 0.84-1.18; P=0.92). During long-term follow-up (median [range], 2.1 [1.0-3.7] years), 11.2% of patients assigned to oxygen and in 10.8% of patients assigned to ambient air died or were hospitalized for heart failure (hazard ratio, 1.02; 95% CI, 0.88-1.17; P=0.84). Cardiovascular death occurred in 5.2% of patients assigned to oxygen and in 4.8% assigned to ambient air (hazard ratio, 1.07; 95% CI, 0.87-1.33; P=0.52).

Robin Hofmann, senior consultant cardiologist and researcher at the department of clinical science and education, Södersjukhuset, at Karolinska Institutet, said: "Our new study has filled a central gap in knowledge regarding how to treat patients suffering a heart attack. One year ago, we were able to confirm that oxygen therapy does not appear to reduce the risk of dying up to one year after the heart attack. We can now substantiate these findings for a long-term perspective and show that oxygen therapy does not reduce the development of heart failure, the most worrying complication of heart attacks. On this basis, the routine use of oxygen can now be eliminated, and healthcare personnel can concentrate on more efficient measures and rapid transport to hospital."

*Jernberg T, Lindahl B, Alfredsson J, et al. Long-Term Effects of Oxygen Therapy on Death or Hospitalization for Heart Failure in Patients With Suspected Acute Myocardial Infarction. Circulation, 2018, DOI:10.1161/CIRCULATIONAHA.118.036220

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