The Association Between Preoperative Hemoglobin A1C and Postoperative Glycemic Variability on 30-Day Major Adverse Outcomes Following Isolated Cardiac Valvular Surgery

Abstract

Background: Preoperative hemoglobin A1c (HbA1c) and postoperative glycemic variability predict major adverse events (MAEs) after coronary artery bypass grafting in a protocolized glycemic control setting. However, the influence of preoperative HbA1c and postoperative glycemic variability in isolated cardiac valvular surgery is unknown. In this study, we sought to establish (a) whether preoperative HbA1c could identify patients at increased risk of MAEs and (b) whether postoperative glycemic variability was associated with MAEs after isolated cardiac valvular surgery.

Methods: Patients >18 years of age undergoing isolated valve surgery from January 2008 to December 2013 were enrolled in this prospective, single-center, observational cohort study with IRB approval. Patient demographics, intraoperative data, and postoperative MAEs were extracted from the institutional Society of Thoracic Surgery (STS) database. The primary outcome, MAEs, was a composite of in-hospital death, myocardial infarction, reoperations, sternal infection, cardiac tamponade, pneumonia, stroke, or renal failure. Glycemic variability in the postoperative period was assessed by the coefficient of variation. Patents were stratified by HbA1c levels (<6.5% or ≥6.5%) and assessed using multivariable logistic regression.

Results: Of the enrolled 763 patients, 109 (14.3%) had a preoperative HbA1c level ≥6.5%. Patients with HbA1c ≥6.5% were older (70 [63-79] vs 66 [56-75], P < .001) and had a higher incidence of dyslipidemia (83.5% vs 57.0%, P < .001) and congestive heart failure (39.5% vs 27.8%, P = .01). The calculated STS risk score for morbidity and mortality was also statistically higher in this group (0.18 [0.13-0.27] vs 0.13 [0.09-0.21], P < .001). The occurrence of MAEs was similar between the 2 groups (13.8% in HbA1c ≥6.5% vs 11.0% in HbA1c <6.5%, P = .40). Multivariate logistic regression analysis revealed that neither preoperative HbA1c ≥ 6.5% (odds ratio [OR] 1.48, 95% confidence interval [CI]: 0.78-2.82; P = .23) nor postoperative glycemic variability (CV per quartile; OR 1.05, 95% CI: 0.85-1.30; P = .67) was found to be associated with MAEs. An HbA1c ≥ 6.5% was associated with the increased glycemic variability in the postoperative period (0.173 [0.129-0.217] vs 0.141 [0.106-0.178], P < .0001).

Conclusions: This study did not show an association between preoperative HbA1c and postoperative glycemic variability with MAEs after isolated cardiac valvular surgery. Specifically, lack of association between postoperative glycemic variability and MAEs is noteworthy and is in contrast to our previous finding in CABG patients. Future studies should focus a targeted glycemic variability reduction in CABG patients and evaluate the reduction in MAEs, without risk of employing a one-size fits all approach when approaching other cardiac procedures.