Effects of Seasonal Variations on the Outcome of Coronary Artery Bypass Graft Surgery

Background: For all the reports on the association between seasons and coronary artery disease, there is a paucity of information on the possible effects of seasonal variations on the outcome of patients after coronary artery bypass grafting surgery (CABG). The aim of this study was to assess the short-term outcome of post-CABG patients in the four different seasons to find any correlation between seasonal variations and the outcome of such patients. Methods: Data on patients who underwent cardiac surgery between 2007 and 2009 were analyzed. In-hospital mortality, length of Intensive Care Unit (ICU) stay, and length of hospital stay in the four different seasons were considered as outcome measures. The EuroSCORE was calculated for all the patients, and the Kruskal-Wallis, Mann-Whitney, Student t, and chi square tests were used as appropriate. Results: Of a total of 402 patients, who underwent CABG during the mentioned period, 292 patients were male (M/F ratio=2.65). There were no differences in terms of mean age, sex ratio, and mean EuroSCORE of the patients between the seasons. The mean length of ICU stay was significantly more in the spring than that of the other seasons (P<0.001), while the difference between the four seasons regarding the mean length of hospital stay did not constitute statistical significance (P=0.22). No effect of seasonal variations was found for the lengths of ICU and hospital stay in the presence of the EuroSCORE after multiple logistic regression analysis (P=0.278, 0.431). Conclusion: Psychological mood changes caused by regional cultural differences rather than environmental factors should be considered in the optimal management of patients after CABG.