ABSTRACT
Coronary artery disease is an atherosclerotic process, with stable and unstable periods. During unstable periods, local inflammatory responses release vasoactive mediators that can cause acute coronary syndromes: ST elevation myocardial infarction, non-ST elevation myocardial infarction, and unstable angina. Myocytes have high metabolic rates, necessitating large quantities of oxygen. The myocardium normally extracts nearly all available oxygen, leaving little reserve for oxygen debt. In health, increased oxygen demand is met either through vasodilatation or tachycardia. While supplementary oxygen is usually needed, hyperoxia can cause cardiac and brain damage, including coronary artery vasoconstriction, so oxygen should be given to achieve target saturations of 94–98%. Myoglobin is not sensitive or specific enough as a cardiac marker. ST elevation myocardial infarction should be treated by primary percutaneous coronary intervention if reasonably possible. If patients are too unstable to transfer, thrombolysis is the next best option.
