CABG Case Volume and Patient Outcomes at the Veterans Healthcare Administration: On-Pump versus Off-Pump

Abstract

Objective: To evaluate use trends and perioperative outcomes of on- and off-pump coronary artery bypass graft (CABG) in US Veterans. Methods: We retrospectively reviewed 44,960 Veteran Health Administration (VHA) patients who underwent isolated CABG between 2008–2021. Multivariable logistic regression was used to analyze associations between surgical technique and outcomes. Adjusted hazard ratios (aHR) are reported. p < 0.05 using two sided tests was considered significant. Results: 6169/44,960 (13.7%) patients underwent isolated off-pump CABG and 38,791/44,960 (86.3%) patients underwent on-pump CABG. Between 2008 and 2021, the proportion of off-pump procedures decreased: 18.8% between 2008–2012, 11.6% between 2013–2017, and 8.6% between 2018–2021 (χ2 = 712.78, df = 2, p < 0.001). Groups were found to be well balanced with respect to age, history of chronic obstructive pulmonary disease (COPD), history of diabetes, history of prior cardiac surgery, as well as left ventricular ejection fraction and history of smoking, and thus an analysis was conducted using the entire cohort. After covariate adjustment, group status was found to not be a predictor of death (aHR = 0.92, 95% confidence interval (95% CI) = 0.66–1.28, p = 0.62), stroke (aHR = 1.33, 95% CI = 0.83–2.12, p = 0.23), myocardial infarction (MI) (aHR = 0.86, 95% CI = 0.51–1.46, p = 0.58). However, given the large imbalance between group size, the groups were then propensity matched on age, history of chronic obstructive pulmonary disease (COPD), diabetes hypertension, smoking, prior cardiac surgery, and left ventricular ejection fraction, resulting in a smaller cohort of 12,130 patients: 5961 (49.1%) on pump and 6169 (50.9%) off pump. After covariate adjustment, the on-pump group in the matched cohort had increased risk of the following within 30 days: death (aHR = 2.60, 95% CI = 1.50–4.51, p < 0.001), stroke (aHR = 1.61, 95% CI = 1.09–2.38, p = 0.016), acute renal failure (aHR = 2.31, 95% CI = 1.46–3.66, p < 0.001), atrial fibrillation (aHR = 1.39, 95% CI = 1.23–1.57, p < 0.001), intraoperative death (aHR = 1.67, 95% CI = 1.07–2.59, p = 0.023), and prolonged intubation (aHR = 1.53, 95% CI = 1.27–1.85, p < 0.001). They also experienced increased length of stay (Beta = 0.05, p < 0.001). Group did not predict risk of reintubation, perioperative myocardial infarction, or postoperative cardiac arrest requiring cardiopulmonary resuscitation (CPR). Conclusions: In a propensity matched cohort of veterans undergoing isolated CABG, off-pump technique was associated with decreased risk of multiple perioperative outcomes measures. However, the proportion of off-pump procedures within the VHA decreased between 2008–2021. This may be secondary to more selective use as overall volume has decreased, though additional study is needed to evaluate these trends.