Objection The diagnosis of postoperative myocardial infarction (PMI) after cardiac surgical procedures is complex and its value remains controversial. In this study we examined the value of cardiac biomarkers to evaluate relevant postoperative coronary injury leading to an intervention.

Methods Between 2016 and 2020 4134 patients underwent cardiac surgical procedures using cardiopulmonary bypass excluding patients undergoing emergency procedures or surgical ablation. Of these, 152 (3,7%) developed a CK-MB level of ≥ 120 U/L, thereby meeting our institutional threshold for diagnostic coronary angiography regardless of whether changes in the EKG were present or not. These patients represent our study cohort. Postoperative CK-MB and hs-TnT levels at 4, 8 and 24 hours as well as on postoperative day 2 and 3 (POD2) were analyzed. The patients were further categorized into three groups (G1-3) according to their catheter results. G1 constitutes patients with new pathology and consecutive intervention, G2 constitutes patients with new pathology without further intervention and G3 represents patients without new postoperative pathology.

Results Among the 152 patients who underwent postoperative angiography due to CK-MB levels of ≥ 120 U/L, 88 patients (57.9%) (G1+2) showed new pathological findings of which 54 (35,5%) underwent consecutive interventions (G1). 64 patients (42.1%)  revealed no pathological findings (G3). Postoperative CK-MB levels in G1+2 were statistically significantly higher at 24 hours and on POD2 than in G3 (p<0.01 and p<0.01). hs-TnT levels of G1+2 revealed significant higher mean values on POD2 and 3 compared to G3 mean levels (p=0.001 and p=0.002). At all other analyzed time points mean CK-MB and hs-TnT levels showed no statistically significant differences between the analyzed groups.

Conclusion In this study, CK-MB levels above 120 U/L proved to be a reliable marker for the detection of a relevant postoperative ischemia with nearly 60 % of CK-MB positive patients actually having new pathological findings upon coronary angiography and 35% receive interventional or surgical treatment. According to our results, CK-MB levels enable an early detection of relevant PMI.