Acute kidney injury and outcome following aortic valve replacement for aortic stenosis

Objectives: Most studies on acute kidney injury (AKI) following open-heart surgery have focused on short-term outcome following coronary artery bypass grafting. We reviewed the incidence, risk factors and outcome, including long-term survival, of AKI after aortic valve replacement (AVR) in a population-based cohort.

Methods: A retrospective review of 365 patients who underwent AVR for aortic stenosis during 2002-2011 was made. AKI was defined according to the RIFLE criteria. All patients requiring dialysis were followed up in a centralized registry. Risk factors for AKI were analysed with univariable and multivariable analysis, and survival was graphically presented with the Kaplan-Meier method.

Results: The rate of AKI was 82/365 (22.5%); 40, 28 and 14 patients belonging to the Risk, Injury and Failure groups, respectively. Preoperatively, 37 (45.1%) AKI patients had reduced kidney function. Transfusion of red blood cells, obesity and prolonged cardiopulmonary bypass time were independent risk factors for AKI. Acute postoperative dialysis was required in 15 patients (4.1%), and 1 patient developed dialysis-dependent end-stage renal disease. Major postoperative complications were more common in the AKI group (65 vs 22%, P < 0.001). The 30-day mortality rate in the AKI group was 18%, as opposed to 2% in the non-AKI group (P < 0.001), with a 5-year survival rate of 66 vs 87%, respectively (P < 0.001). In multivariable analysis AKI was an independent predictor of operative mortality [odds ratio = 5.89, 95% confidence interval (CI) = 1.99-18.91] but not of long-term survival (hazard ratio = 1.44, 95% CI = 0.86-2.42).

Conclusions: More than 1 in 5 patients (22.5%) who underwent AVR developed AKI postoperatively. AKI was associated with higher morbidity and was an independent predictor of operative mortality. However, AKI was not a determinant of long-term survival.