The significance of myocardial enzyme elevations following coronary artery bypass surgery (CABG) remains controversial. Although a ‘significant’ enzyme rise is felt to indicate a worse long-term prognosis, several smaller studies have suggested that even small enzyme rises within 24hours of surgery are significant. This analysis aimed to define whether a threshold exists below which enzyme rises can be deemed insignificant.
18,908 patients were included from seven studies that had measured cardiac markers with 24 hours of CABG; follow-up varyied from three months to five years. Of all variables considered, the CK-MB ratio was the strongest independent predictor of death to 30 days, and this remained the case even after adjustment for baseline risk factors. Furthermore, mortality was found to increase monotonically with CK-MB ratio; a ratio of <1 was associated with 0.63% mortality at 30 days, while a ratio of over 40 was associated with 30 day mortality of 7.06%. Similar findings were seen when troponin was used as the main marker of necrosis.
Following CABG, an early (within 24 hours) elevation of CK-MB or troponin is independently associated with a higher risk of mortality in the intermediate and longer term.
- Domanski MJ, Mahaffey K, Hasselblad V et al. Association of Myocardial Enzyme Elevation and Survival Following Coronary Artery Bypass Graft Surgery. JAMA 2011; 305: 585-591.