Oxidative Stress in Coronary Artery Surgery

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Post-operative atrial fibrillation (POAF) is one of the most common complications after coronary artery surgery, affecting 20-50% of patients. It is a serious post surgical complication that is associated with increased morbidity and long-term health care costs. The development of this arrhythmia after surgery is multi-factorial and reliable pre-operative predictors have not been found. The inability to reliably predict patients at risk means that current methods of preventing POAF remain suboptimal. Mounting evidence suggests that increased reactive oxygen species and oxidative stress play a major part in POAF development, opening the possibility of antioxidant supplementation as a preventative measure. During cardiac surgery with cardiopulmonary bypass (CPB), increases in reactive oxygen species occurs after blood contact with the CPB circuit, the inflammatory response syndrome, ischemia-reperfusion and hyperoxia resulting in oxidative damage to myocytes. In addition there is also a reduced antioxidant response. Some of the primary antioxidants rely on appropriate levels of trace elements for normal function. One such trace element is selenium, which is required by the antioxidant glutathione peroxidase. Reductions in selenium during and after surgery are associated with increased mortality. This observational study will measure oxidative stress levels (by malondialdehyde), as well as selenium levels, pre-, intra- and up to 5 days post-operatively, to determine if an association exists between these levels and the development of POAF. The study will separate participants into patients at low risk of post-operative mortality and those at high risk. In this way we hope to better define the effect of pre- and intra-operative low levels of selenium (and increases in oxidative stress) on events such as POAF. Understanding the pathophysiological differences of low selenium between various patient risk groups may lead to targeted pre-operative antioxidant therapies that have better success at preventing POAF.

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