Association Between Electrocardiographic Changes and Myocardial Injury or Death After Cardiac Surgery

BACKGROUND: The relationship between myocardial injury after cardiac surgery (MICS), ischemia on electrocardiogram (ECG), and mortality is uncertain. In this study we aimed to determine whether potential ischemic ECG changes after cardiac surgery are associated with 30-day mortality. METHODS: In a cohort of adults who underwent cardiac surgery, experts interpreted ECGs preoperatively; on postoperative days 0, 1, 2, and 3; and on the last day before discharge (59,539 total ECGs reviewed) for new potential ischemic ECG changes. RESULTS: Among 12,594 patients, 9097 (72.2%) had potential ischemic ECG changes; 259 (2.1%) died within 30 days after surgery. Among patients with troponin elevation meeting MICS criteria, in models adjusting for EuroSCORE II, the hazard ratio (HR) for 30-day mortality was 0.57 (95% confidence interval [CI] 0.35-0.94, P = 0.03) for new Q waves, 2.17 (95% CI 1.14-4.13, P = 0.02) for ST depression ≥ 2 mm, and 0.58 (95% CI 0.39-0.87, P = 0.007) for T-wave inversion 1-1.9 mm. ST elevation was not significantly associated with 30-day mortality. The only ECG change for which coronary artery bypass grafting (CABG) was an effect modifier was new left bundle branch block (LBBB), with an HR of 2.78 (95% CI 1.69-4.60, P = 0.0001) with CABG and an HR of 1.10 (95% CI 0.54-2.21, P = 0.27) without CABG (P value for interaction = 0.03). CONCLUSIONS: After cardiac surgery, potential ischemic ECG changes are common and have divergent associations with mortality. ST depression was associated with a higher risk of death, whereas new Q waves and T-wave inversions were associated with a lower risk of death. A new LBBB was associated with a higher risk of death only among patients who underwent CABG. Potential ischemic ECG changes are common after cardiac surgery and lack specificity for the diagnosis of myocardial infarction.