Abstract 4169: Defining Myocardial Injury and Function Following Coronary Artery Bypass Grafting: Insights From Serial Cardiovascular Magnetic Resonance Imaging and Biochemical Assessment
Background: Using Cardiac magnetic resonance (CMR) we examined the utility of cardiac biomarkers to determine myocardial injury and function after coronary artery bypass grafting (CABG), and tested the recently updated guidelines for the diagnosis of post-operative myocardial infarction (Type V MI).
Methods: In a single centre randomised trial, 50 patients with impaired ventricular function were randomly assigned between two operative techniques for CABG. Patients underwent CMR for left ventricular function and delayed hyperenhancement (DE) before and 6 days after surgery, with serial assessment of troponin (cTnI), CKMB and B-Type Natriuretic Peptide (BNP).
Results: AUC for cTnI strongly correlated with mass of DE (r=0.83, p<0.001). Furthermore, routine assessment of cTnI at 24 hours (>6.6μg/L) predicted Type V MI on DE-CMR with a sensitivity of 88% and specificity 97%, whereas the clinical application of the new AHA/ESC criteria had a sensitivity 13% and specificity 100%. The associations with CKMB were less robust (r=0.58, p<0.001). Despite moderate pre-operative associations between BNP and ejection fraction (EF r=0.40, p<0.05), post operative levels correlated with AUC for cTnI (r=0.503, p<0.001), but not early cardiac function.
Conclusion: Biomarkers alone (cTnI), at an appropriate threshold appear robust for the detection of Type V MI, without the use of supplementary evidence as suggested by the AHA/ESC criteria.