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Impact of preoperative renal dysfunction in patients undergoing off-pump versus on-pump coronary artery bypass
Bryon J Boulton1, Patrick Kilgo, Robert A Guyton
1Clinical Research Unit, Division of Cardiothoracic Surgery, Rollins School of Public Health, Emory University School of Medicine, Atlanta, Georgia 30308, USA.
Insights
Renal dysfunction (RD) significantly impacts survival after coronary artery bypass grafting (CABG). Even mild RD increases mortality risk, with severe RD and dialysis dependence drastically worsening outcomes and long-term survival.
Area of Science:
- Cardiology
- Nephrology
- Surgical Outcomes
Background:
- The influence of varying degrees of renal dysfunction (RD) on outcomes following coronary artery bypass grafting (CABG) remains incompletely understood.
- Patients undergoing CABG present with a spectrum of renal function, from normal to end-stage renal disease requiring dialysis.
Purpose of the Study:
- To investigate the association between preoperative renal dysfunction and both in-hospital and long-term mortality in patients undergoing isolated, primary CABG.
- To compare outcomes between on-pump and off-pump CABG in patients with different levels of renal dysfunction.
Main Methods:
- A retrospective analysis of 14,199 patients undergoing primary CABG between 1996 and 2009.
- Renal function was categorized by estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease formula: normal, mild (60-90 mL/min/1.73 m²), moderate (30-59 mL/min/1.73 m²), and severe (<30 mL/min/1.73 m²), plus dialysis dependence.
- Propensity scoring and multivariable regression analyses were employed to adjust for preoperative covariates and assess the independent impact of eGFR on mortality and survival.
Main Results:
- Preoperative renal dysfunction was prevalent, affecting over 75% of the CABG population (mild RD: 51.0%, moderate RD: 20.1%, severe RD: 2.0%, dialysis: 2.2%).
- Moderate to severe RD and dialysis dependence were independently associated with significantly worse adjusted in-hospital mortality (ORs ranging from 3.55 to 9.64, p<0.05).
- Adjusted long-term survival was progressively worse across all levels of renal dysfunction compared to patients with normal eGFR. Off-pump CABG showed worse long-term survival in moderate-to-severe RD patients compared to on-pump CABG.
Conclusions:
- Preoperative renal dysfunction is a common and significant independent predictor of diminished long-term survival following CABG.
- While off-pump CABG may offer early benefits in patients with RD, this advantage diminishes with increasing severity of renal dysfunction, highlighting the critical impact of kidney function on surgical outcomes.
Background:
The impact of the degree of renal dysfunction (RD) in patients undergoing coronary artery bypass grafting (CABG) ranging from normal to dialysis-dependence is not well defined.
Methods:
A retrospective review of 14,199 patients undergoing isolated, primary CABG from January 1996 to May 2009 at Emory Healthcare was performed. The estimated glomerular filtration rate (eGFR) was estimated by the Modification of Diet in Renal Disease formula: mild RD (eGFR 60 to 90 mL/min/1.73 m2), moderate RD (eGFR 30 to 59), severe RD (eGFR<30). A propensity scoring was used to balance the groups with 46 preoperative covariates. Multivariable logistic and Cox regression methods were used to determine the independent association of eGFR with mortality. Adjusted odds ratios were calculated for outcomes using the normal eGFR group as the reference. Kaplan-Meier curves were created to estimate long-term survival.
Results:
A total of 8,086 patients (57.0%) underwent off-pump coronary artery bypass (OPCAB) while 6,113 (43.0%) underwent on-pump CAB. Preoperative RD was common: Normal eGFR (n=3,503/14,199 [24.7%]); mild RD (7,236/14199 [51.0%]); moderate RD (2,860/14,199 [20.1%]); severe RD (283/14,199 [2.0%]); and preoperative dialysis (317/14,199 [2.2%]). Moderate to severe RD or preoperative dialysis was associated with worse adjusted in-hospital mortality: mild RD (odds ratio [OR] 1.42; 95% confidence interval [CI] 0.93 to 2.16; p=not significant); moderate RD (OR 3.55; 95% CI 2.32 to 5.43; p<0.05]; severe RD (OR 8.84; 95% CI 4.92 to 15.9; p<0.05); and dialysis-dependent (OR 9.64; 95% CI 5.45 to 17.0; p<0.05). Adjusted long-term survival was worse across levels of RD. The OPCAB patients with moderate to severe RD had worse long-term survival than on-pump CAB patients; however, the surgery types were similar among normal, mild, and dialysis patients.
Conclusions:
Preoperative RD is common in the CABG population and is associated with diminished long-term survival. Improved early outcomes in patients with RD undergoing OPCAB diminished with worsening RD.
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