The aim of SOCCER is to evaluate the effects of treatment with supplemental O2 before and during acute balloon angioplasty (PCI) for patients with ST-elevation myocardial infarction (STEMI). One hundred STEMI patients are randomized in the ambulance to either standard O2 treatment (10 l/min) or no supplemental O2, to be given until the end of the acute PCI. Cardiac magnetic resonance imaging and echocardiography during the hospital stay is used to assess infarct size and myocardial performance. All patients are followed for 6 months. At 6 months, perceived health and NT-proBNP are recorded for all patients, and an additional echocardiography is performed. The primary endpoint is the fraction of myocardium saved with the acute PCI. The secondary endpoints include the pain difference between inclusion time and start of PCI and myocardial performance on echocardiography.

Almost all patients with ST elevation myocardial infarction (STEMI) in Sweden undergo acute balloon angioplasty (PCI) to open the occluded coronary artery, and thereby to reduce or abolish the myocardial infarction. Standard treatment in these cases is 10-15 l of supplemental oxygen to reduce the myocardial ischemia and the infarct size. It is, however, unknown whether supplemental O2 is beneficial or detrimental to patients with STEMI undergoing PCI.

This study aims to evaluate the effects of treatment with supplemental O2 in acute PCI for STEMI.

The study is a multicenter single blind parallel group randomized trial. One hundred normoxic STEMI ambulance patients accepted for primary PCI are randomized in the ambulance to either standard O2 treatment (10 l/min) or no supplemental O2, to be given until the end of the acute PCI. All patients undergo cardiac MRI at day 4-6 to determine area at risk, infarct size and myocardial salvage index. Fifty patients undergo an extended echocardiography during the hospital stay to assess infarct size and wall motion score index. All patients are followed for 6 months. At 6 months, perceived health (EQ-5D) and NT-proBNP are recorded for all patients, and an additional echocardiography is performed for the subgroup of 50 patients. The primary endpoint is myocardial salvage index. Secondary endpoints include pain difference between inclusion time and start of PCI and wall motion score index on echocardiography.

Inclusion Criteria:

• STEMI patient transported with ambulance to SUS Lund or Malmö or Helsingborg hospital, and accepted for acute PCI
• Symptom duration less than 6 hours
• Normal SaO2 (≥ 94 %) measured with pulse oximeter
• Informed consent

Exclusion Criteria:

• Previous AMI
• Inability to make decision to participate; dementia and the like
• For CMR: Significant claustrophobia, prostheses or other magnetic material inside the body