Objectives: Exploring the long-term consequences of elevated postoperative creatine phosphokinase MB as a surrogate measure of cardiac tissue damage subsequent to coronary artery bypass graft surgery (CABG). Methods: Prospective cohort study including 414 patients subjected to solitary CABG at Odense University Hospital from September 30, 2007, and backwards in time. According to individual postoperative peak creatine phosphokinase MB, patients were assigned to five subgroups. Kaplan Meier survival analysis and Cox proportional-hazard regression evaluated the predictive value of creatine phosphokinase MB on late death from cardiac cause and diagnosis of paroxysmal or persistent atrial fibrillation within 10-years after CABG. Results: There was a general numeric decrease in time to cardiac death with increasing postoperative creatine phosphokinase MB (Log-Rank 0.285). Creatine phosphokinase MB < 25 was significantly associated with both shortened extracorporeal circulation time (HR 0.42; 95% CI 0.30-0.57; p < 0.001) and aortic cross-clamp time (HR 0.54; 95% CI 0.40-0.73; p < 0.001) compared to creatine phosphokinase MB ≥ 100. No association between creatine phosphokinase MB and atrial fibrillation was identified. Postoperative atrial fibrillation occurred in 84 patients, whereof 21 later developed paroxysmal or persistent atrial fibrillation. There was a statistically significant 2.4-fold (HR 2.38; 95% CI 1.37-4.14; p = 0.002) increase in paroxysmal or persistent atrial fibrillation in patients with postoperative atrial fibrillation compared to patients in postoperative sinus rhythm. Conclusions: Postoperative creatine phosphokinase MB was not found predictive of late cardiac death or diagnosis of paroxysmal or persistent atrial fibrillation within 10 years after CABG. However, patients with postoperative atrial fibrillation had increased risk of later developing paroxysmal or persistent atrial fibrillation compared to patients in postoperative sinus rhythm.