Treat Oxygen as a Drug in STEMI Patients

Oxygen is commonly administered to patients with ST-elevation myocardial infarction (STEMI) despite previous studies that suggested a possible increase in myocardial injury as a result of coronary vasoconstriction and heightened oxidative stress.

A presentation at the American Heart Association (AHA) Scientific Sessions 2014 suggested, STEMI victims treated with oxygen endured 25 to 30% more heart damage than patients not given oxygen.

Dion Stub, MBBS, PhD, of the Baker IDI Heart and Diabetes Institute, Melbourne, Australia said, “This study backs up previous research that shows oxygen should be treated as a drug, and prescribed appropriately. If a heart attack patient’s oxygen levels are normal, you should not give them oxygen.”

According to Stub, high oxygen levels not only cause arteries to constrict and change blood pressure, but they also significantly reduce the amount of blood pumped through the heart.

Stub and his team randomized a total of 638 individuals in a multicenter, prospective, controlled trial that was designed to compare oxygen (8 L/min) with no supplemental oxygen in patients with STEMI diagnosed on paramedic 12-lead electrocardiogram. Only 441 were confirmed STEMI patients who subsequently underwent primary endpoint analysis.

There was an increase in the rate of recurrent myocardial infarction in the oxygen group compared to the no oxygen group, and an increase in frequency of cardiac arrhythmia. At 6-months the oxygen group had an increase in myocardial infarct size as well. Additionally, results showed the oxygen exhibited 30% more damage to their heart muscle than those in the non-oxygen group.

Stub said, “The primary endpoint was myocardial infarct size as assessed by cardiac enzymes, troponin (cTnl), and creatine kinase (CK). The secondary endpoints included recurrent myocardial infarction, cardiac arrhythmia, and myocardial infarct size assessed by cardiac magnetic resonance (CMR) imaging at 6 months.”

The study results concluded, “Supplemental oxygen therapy in patients with STEMI but without hyopexia increased early myocardial injury and was associated with larger myocardial infarct size assessed at 6 months.”

Stub commented on the necessity of further research to specifically study death rates and level of heart damage.