Acute kidney injury is not only common after implantation of a left ventricular assist device, it is also an independent predictor of 30-day and 1-year all-cause mortality, according to a retrospective, single-institution study.
In addition, multivariate analysis showed that only diabetes was a significant predictor of post-LVAD implantation acute kidney injury (AKI), the investigators stated in the report published online Feb. 15 in the American Journal of Nephrology.
Dr. Abhijit Naik and Dr. Jay L. Koyner of the section of nephrology at the University of Chicago and their colleagues identified 168 patients who underwent LVAD implantation at the university. They excluded 11 patients because of previous end-stage renal disease and intraoperative mortality. The remaining cohort of 157 patients served as their study population, which was 78% men and 58% white and had a mean age of around 57 years (Am. J. Nephrol. 2014 Feb. 15 [doi:10.1159/000358495]).
Dr. Jay Koyner
The obtained demographic, biochemical, and clinical profiles from the national Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS), the Society of Thoracic Surgeons (STS) database, and the University of Chicago medical record (EMR). Baseline creatinine was defined as the listing of creatinine data obtained from the INTERMACS registry, or failing that, the last serum creatinine in the EMR prior to device implantation.
They defined the primary outcome of AKI as a 50% rise in serum creatinine over the preoperative baseline during the first 7 postoperative days. All-cause mortality was monitored over 1 year after implantation, with data reported at 30 and 365 days.
A total of 44 of 157 (28%) of patients developed AKI based on the study criteria. The only significant baseline differences between the patients with and without AKI were the presence of diabetes and cerebrovascular disease (CVD), each significantly higher in the patients who developed AKI.
Univariate analysis showed CVD and diabetes as significant predictors of developing AKI, but upon multivariate analysis, only diabetes retained significance (odds ratio, 2.27; P = .04).
As for mortality, only AKI (hazard ratio, 3.01; P = .03) and cardiopulmonary bypass time (HR, 1.01; P = .02) were significant predictors of 30-day mortality. Preoperative diabetes mellitus (HR, 1.9; P = .03) or postimplantation AKI (HR, 1.85; P = .03) were significant independent predictors of 1-year mortality. Higher preoperative body mass index was significantly and slightly protective (HR, 0.95; P = .03).
The authors stated that the strength of their study was that it is the largest cohort study of LVAD patients to employ a consensus definition of AKI; limitations were its single-center and retrospective nature and the use of database reviews.
As AKI is a common adverse outcome following traditional cardiac surgery, including coronary artery bypass grafting and/or valve replacement, more research is needed to tease out any differences unique to LVAD implantation, the investigators said.
"Given the high AKI rates and the mounting evidence linking AKI to mortality following VAD implantation, the use of biomarkers to identify patients at risk may have a role. Large prospective multicenter trials are needed to develop a risk stratification system to identify patients at risk for developing post-VAD implantation AKI," the researchers concluded.
Dr. Koyner was supported by a K23 grant from the National Institutes of Health. One of the coauthors reported research funding from Thoratec and another reported consulting fees from Thoratec and HeartWare. The other authors reported no disclosures.