Effect of myocardial scar detected from cardiac magnetic resonance imaging on cardiovascular events after coronary artery bypass grafting

Background Cardiac MRI is a valuable tool for preoperative myocardial assessment before coronary artery bypass grafting (CABG), enabling the evaluation of myocardial scar, wall thickness, and ventricular size. Previous studies have demonstrated that the extent of non-viable scar is associated with increased mortality and postoperative cardiovascular events (CVEs). However, no statistically significant difference in mortality rates between patients with and without myocardial scar was observed in one of those studies, and the effect of scar presence on postoperative CVEs remains unclear. Purpose This study investigates the impact of presence of myocardial scar and its characteristics—including scar extension, transmurality, wall thinning, and chamber enlargement—on postoperative CVEs. Methods A retrospective review was conducted on patients who underwent preoperative cardiac MRI prior to CABG at our hospital between 2015 and 2022. Patients were categorized into "with scar" and "without scar" groups based on MRI findings. CVEs at 30 days and 1 year postoperatively including low cardiac output syndrome, cardiovascular death, stroke, ventricular arrhythmia which need AICD implantation, congestive heart failure, and perioperative myocardial infarction were compared. Univariate and multivariate analyses were performed to identify factors associated with postoperative CVEs. Results Among 108 patients (50 with scar, 58 without scar), baseline characteristics were largely comparable, except for a lower prevalence of hypertension and a higher EuroScore II in the with scar group. This group also demonstrated lower left ventricular ejection fraction (LVEF) and larger left ventricular (LV) size. CVEs were significantly higher in the with scar group at both 30 days (44% vs. 17.2%, p = 0.002) and 1 year (60% vs. 20.7%, p < 0.001). Univariate analysis identified associations with scar involving >2 segments, scar area >2%, left anterior descending (LAD) artery scar, larger LV size, and wall thinning. In multivariate analysis, LV end diastolic diameter (LVEDD) >55 mm and interventricular septal thickness (IVS) <7.5 mm were independent predictors of CVEs. Conclusions The presence of preoperative myocardial scar is significantly associated with increased postoperative CVEs at both 30 days and 1 year. Notably, chamber enlargement (LVEDD >55 mm) and wall thinning (IVS <7.5 mm) emerged as key parameters associated with higher risk.