Increased Plasma Mitochondrial DNA Copy Number and Association with Complications after Coronary Artery Bypass Grafting: Results of a Pilot Cohort Study

Objective — To determine the mitochondrial DNA (mtDNA) copy number in the blood of patients before and within 10 days after coronary artery bypass grafting (CABG) and to evaluate the association between mtDNA copy number and postoperative complications. Methods — This single-center, prospective, unblinded cohort study included 26 patients undergoing CABG with a median age of 67 years (interquartile range [IQR]: 58-71). Plasma and peripheral blood mononuclear cells (PBMCs) were collected from patients before CABG and at 3, 5, 7, and 10 days after CABG. MtDNA copy number was measured using digital polymerase chain reaction. Results — In plasma, the median mtDNA copy number in million copies per mL was 5.12 (3.35-7.44) before CABG, 2.65 (1.88-3.04) on Day 3, 4.04 (2.28-7.00) on Day 5, 6.50 (3.47-11.31) on Day 7, and 10 (7.2-13.4) on Day 10. The median mtDNA copy number in PBMCs was 79 (63.5-95.2) copies/cell before CABG; it did not change statistically significantly after CABG (p>0.05). Patients with complications had a significant increase in plasma mtDNA copy number (198%; IQR: 101; 321) vs. patients without complications (11%; IQR: -36; 127%; p=0.008). Conclusion — Based on the results of our pilot study, an increase in mtDNA copy number by Day 10 after CABG is associated with postoperative complications. The mtDNA copy number in PBMCs did not change significantly after CABG.