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Impact of Preoperative Renal Dysfunction on Mortality and Postoperative Outcomes in Mitral Valve Surgery
Xiaoying Lou, Jessica Forcillo, Michael Halkos, Jose Condado-Contreras, Jose Binongo, Yi Lasanajak, Douglas Murphy, Robert Guyton, Jeffrey Miller, Edward Chen, Omar Lattouf, Bradley Leshnower, Brent Keeling, Vinod Thourani.
Emory University, Atlanta, GA, USA.

Background.
The impact on morbidity and mortality of the level of renal dysfunction (RD) prior to mitral valve (MV) surgery has not been well-described. We compared outcomes in patients undergoing MV surgery with preoperative renal function ranging from normal to dialysis-dependent.
Methods.
A retrospective review of 2,658 patients undergoing MV surgery (repair and replacement) from 1/2005-12/2015 was performed. Glomerular filtration rate (GFR) was estimated using the MDRD formula: mild RD (GFR 60-90 mL/min/1.73 m2), moderate RD (GFR 30-59 mL/min/1.73 m2), severe RD (GFR 15-29 mL/min/1.73 m2), and dialysis-dependent (GFR <15 mL/min/1.73 m2). Multivariable logistic regression was used to determine the association of GFR with outcomes. Adjusted odds ratios were calculated for in-hospital outcomes, and Kaplan-Meier curves were generated to estimate survival.
Results.
Preoperative RD was common among all patients: 1,221 (45.9%) with mild RD, 524 (19.7%) moderate RD, 63 (2.4%) severe RD, and 86 (3.2%) on dialysis. In-hospital mortality rose with worsening RD, from 1.1% for patients without RD to 10.5% for those on dialysis (p<0.01). Adjusted five-year survival was worse across all levels of RD (p<0.01): 89.6%, 77.8%, 65.1%, and 42.5%, for patients with mild RD, moderate RD, severe RD, and on dialysis, respectively (FIGURE). Worsening levels of RD, older age at presentation (OR 1.06, 95% CI:1.03-1.08, p<0.01), and presence of diabetes mellitus (OR 2.06, 95% CI:1.22-3.48, p<0.01), angina (OR 2.45, 95% CI:1.21-4.97, p=0.01), and prior myocardial infarction (OR 1.97, 95% CI:1.08-4.97, p=0.03) predicted operative mortality. When evaluating outcomes based on operative technique, 1,945 patients (73.2%) underwent MV repair and 713 (26.8%) underwent replacement. After adjustment for baseline variables, worsening preoperative RD was associated with increased in-hospital and mid-term mortality as well as morbidity in patients undergoing repair but not replacement.
Conclusions.
Preoperative RD is common among patients undergoing MV surgery and is an independent predictor of in-hospital mortality. Interestingly, worsening levels of RD is associated with increased mid-term mortality in patients undergoing MV repair but not replacement, highlighting an area warranting further investigation.


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