Inhospital outcome of acute myocardial infarction in patients with prior coronary artery bypass surgery.

OBJECTIVES Our goals were to compare the characteristics of patients with and without prior coronary artery bypass graft (CABG) presenting with acute myocardial infarction (MI) with or without ST elevation/left bundle branch block (LBBB), and to evaluate the effect of ST shift on inhospital mortality. METHODS AND RESULTS Using the National Registry of Myocardial Infarction-3 Registry, we identified 112,697 patients with acute MI without exclusion criteria. Of these, 15,936 (14.1%) had prior CABG. Patients with prior CABG had more adverse characteristics and were less likely to have ST elevation/LBBB than patients without prior CABG. The unadjusted mortality for ST elevation/LBBB patients was higher in patients with prior CABG versus without (16.2% vs 14.1%, P =.0001), whereas in patients without ST elevation/LBBB, prior CABG conferred a lower unadjusted mortality versus without (10.1% vs 12.4%, P =.0001). Adjusting for baseline differences, prior CABG was weakly associated with inhospital mortality in ST elevation/LBBB patients (odds ratio [OR], 1.11, 95% CI 1.00-1.23), but not in patients without ST elevation/LBBB (OR 0.99, 95% CI 0.92-1.07). CONCLUSION Acute MI patients with prior CABG are more likely to present without ST elevation/LBBB than patients without prior CABG. Prior CABG was weakly associated with inhospital mortality in patients with ST elevation/LBBB, but not in patients without these electrocardiographic findings. This suggests the differences in absolute mortality rates between patients presenting with MI with and without a history of prior CABG are largely caused by differences in baseline characteristics and presentation.