Cardiac magnetic resonance imaging predictors of short-term outcomes after high risk coronary surgery

Background: The euroSCORE II is a widely used pre-coronary artery bypass graft surgery (CAGS) risk score, but its predictive power lacks the specificity to predict outcomes in high-risk patients (<LVEF 40%) due to changes in cardiac surgery case mix, revascularisation techniques and related outcomes in recent years. We investigated the utility of Cardiac Magnetic Resonance Imaging (CMRI) in predicting immediate and six-week outcomes after CAGS. Methods: Fifty-two consecutive patients with high euroSCORE II (>16) and left ventricular (LV) dysfunction (<40%) based on 2D-echocardiography who underwent CAGS and in whom CMRI (1.5T) was performed preoperatively were retrospectively studied. Cardiac magnetic resonance imaging parameters were assessed in patients who either had complications immediately post-surgery (n=35), six weeks post-surgery (n=20) or were uncomplicated. Results: The average age of patients recruited was 69±5 years with high euroSCORE II (22±4) and low 2D-echocardiography LV ejection fraction (38%±2%). Cardiac magnetic resonance imaging results demonstrated that those with immediate complications had higher LV scar/infarct burden as a proportion of LV mass (17±3% vs 10±3%; p=0.04) with lower circumferential relaxation index (2.5±0.46 vs 2.8±0.56; p=0.05) compared to those with no complications. Early mortality from surgery was 17% (n=9) and was associated with lower RV stroke volume (55±12 vs 68±18; p=0.03) and higher LV infarct scar/burden (18±2% vs 10±2%, p=0.04). Cardiac magnetic resonance imaging showed patients with complications at six weeks post-surgery had higher LV scar/infarct burden (14.5±2% vs 6.8±2%, p=0.03) compared to those without complications. Conclusion: Cardiac magnetic resonance imaging preoperative LV and RV parameters are valuable in assessing the likelihood of successful outcomes from CAGS in high-risk patients with LV dysfunction.