Utility of Glycated Hemoglobin Screening in Patients Undergoing Elective Coronary Artery Surgery

Background: Patients with increased glycated hemoglobin (HbA1c) seem to be at increased risk of sternal wound infection (SWI) after coronary artery bypass grafting (CABG). However, it is unclear whether increased baseline HbA1c levels may also affect other postoperative outcomes.

Methods: Data on preoperative levels of HbA1c were collected from 2606 patients undergoing elective isolated CABG from 2015 to 2016 and included in the prospective, multicenter E-CABG registry.

Results: The prevalence of HbA1c ≥53mmol/mol (7.0%) among non-diabetics was 5.3%, among non-insulin dependent diabetics 53.5% and among insulin dependent diabetics 67.1% (p < 0.001). The prevalence of HbA1c >75 mmol/mol (9.0%) among non-diabetics was 0.5%, among non-insulin dependent diabetics 5.8% and among insulin dependent diabetics 10.6% (p < 0.001). A baseline level of HbA1c ≥53mmol/mol (7.0%) was a significant predictor of SWI (10.7% vs 3.3%, adjusted p-value < 0.001), deep SWI/mediastinitis (3.8% vs 1.3%, adjusted pvalue 0.001) and acute kidney injury (27.4% vs 19.8%, adjusted p-value 0.042). In patients without history of diabetes, HbA1c ≥53mmol/mol (7.0%) was predictive of postoperative stroke (5.9% vs 0.8%, p < 0.001); in patients with diabetes, HbA1c ≥53mmol/mol (7.0%) was only predictive of SWI (11.1% vs 4.8%, p = 0.001). Among patients undergoing single internal mammary artery grafting, the rates of SWI (crude rates, HbA1c < 53mmol/mol: 2.4%; 53–75mmol/mol: 9.0%; > 75mmol/mol: 13.3%, adjusted p-value < 0.001) as well as deep SWI/mediastinitis (crude rates, HbA1c < 53mmol/mol: 0.9%; 53–75mmol/mol: 3.2%; > 75mmol/mol: 5.0%, adjusted p-value 0.016) increased significantly along with increasing HbA1c. Among patients undergoing bilateral internal mammary artery grafting, the rates of SWI (crude rates, HbA1c < 53mmol/mol: 4.1%; 53–75mmol/mol: 9.6%; >75mmol/mol: 17.1%, adjusted p-value 0.002) increased significantly along with increasing HbA1c, whereas a trend was observed for deep SWI/mediastinitis (crude rates, HbA1c < 53mmol/mol: 1.7%; 53–75mmol/mol: 3.3%; >75mmol/mol: 7.3%, adjusted p-value 0.170).

Conclusions: Patients with increased HbA1c levels are at higher risk of SWI, deep SWI/mediastinitis and acute kidney injury. With increasing HbA1c values, the rates of SWI and deep SWI/mediastinitis are increasing in patients receiving single or bilateral internal mammary artery grafting. In patients without history of diabetes, elevated HbA1c values were predictive of postoperative stroke.