Early and late prognostic implications of coronary artery bypass timing after myocardial infarction

The optimal timing of coronary artery bypass grafting (CABG) after myocardial infarction (MI) is still controversial. With advances in perioperative care and myocardial protection, CABG is not infrequently undertaken sooner. Although CABG soon after MI is associated with high morbidity and mortality, the impact of CABG timing on late survival is not clear.

We analysed prospectively collected data for 8320 patients who underwent primary CABG from 1996 through 2010. Operative outcomes and late survival were compared between patient categories based on MI-to-CABG days: groups A (0-30, n = 658), B (31-60, n = 734), C (>90, n = 2698) and D (no MI, n = 4230). The effect of the timing of surgery on survival was determined using multivariate and Kaplan-Meier analyses.

As the MI-to-CABG interval increased, the frequency of urgent/emergency operations decreased and hospital mortality (A, 3.5% vs B, 2.6% vs C, 1.2%, vs D, 1.1%, P < 0.0001) steadily declined. In general, patients who had CABG within 90 days of MI had more cardiac morbidity and co-morbidities. Expectedly, therefore, postoperative organ system dysfunction (cardiac, renal, respiratory and neurological) was more frequent in these groups. Reoperation for bleeding was similar for all groups, but blood product transfusion decreased as the MI-to-CABG days increased. The 10-year survival improved with the MI-to-CABG interval (A, 72.2% vs B, 73.4% vs C, 75.8% vs D, 81.4%, P < 0.0001). By multivariate analysis, the MI-to-CABG interval was not a risk factor for operative or late mortality. However, less frequent were left internal mammary artery use, non-elective surgery and high blood transfusion rates; all more often associated with shorter MI-to-CABG intervals.

Early and late mortality risk for CABG declines with increasing interval from MI for reasons indirectly linked to the timing of surgery. Our findings emphasize the importance of preoperative organ system optimization and consistent left internal mammary artery use, regardless of the proximity of surgery to MI or the exigency of surgery.