Air Versus Oxygen in ST-Segment-Elevation Myocardial Infarction.

Area of Science:

• Cardiology
• Emergency Medicine
• Critical Care Medicine

Background:

• Routine oxygen administration is common for ST-elevation myocardial infarction (STEMI) patients.
• Concerns exist regarding potential harm from oxygen, including coronary vasoconstriction and increased oxidative stress.
• Previous studies have yielded conflicting results on oxygen's effects in STEMI.

Purpose of the Study:

• To investigate the impact of supplemental oxygen on myocardial injury and infarct size in STEMI patients without hypoxia.
• To evaluate secondary outcomes such as recurrent myocardial infarction and cardiac arrhythmias.

Main Methods:

• A multicenter, prospective, randomized controlled trial was conducted.
• 638 patients with STEMI diagnosed by paramedic ECG were randomized to receive oxygen (8 L/min) or no supplemental oxygen.
• Primary endpoint was myocardial infarct size assessed by cardiac enzymes (troponin I, creatine kinase); secondary endpoints included recurrent MI, arrhythmia, and MRI-assessed infarct size at 6 months.

Main Results:

• Mean peak troponin levels were similar between groups (P=0.18).
• Mean peak creatine kinase was significantly higher in the oxygen group (P=0.01).
• The oxygen group showed increased rates of recurrent myocardial infarction (5.5% vs 0.9%, P=0.006), cardiac arrhythmia (40.4% vs 31.4%, P=0.05), and larger infarct size at 6 months (20.3g vs 13.1g, P=0.04).

Conclusions:

• Supplemental oxygen therapy for STEMI patients without hypoxia may increase early myocardial injury.
• Oxygen administration was associated with larger myocardial infarct size at 6 months.
• Findings suggest reconsidering routine oxygen use in normoxic STEMI patients.