Impact of Varying Degrees of Renal Dysfunction on Transcatheter and Surgical Aortic Valve Replacement

Study Questions:

Does pre-existing renal impairment affect hospital mortality or length of stay among patients undergoing transcatheter (TAVR) compared to surgical aortic valve replacement (SAVR)?

Methods:

A retrospective review was performed of 1,336 patients undergoing SAVR (2002-2012) and 321 patients undergoing TAVR (2007-2012). Patients were divided into three groups based on glomerular filtration rate (GFR): GFR >60 ml/min, GFR 31–60 ml/min, and GFR ≤30 ml/min. Logistic and linear regression analyses were performed to estimate the TAVR effect on outcomes. Risk adjustments were made using the Society for Thoracic Surgeons (STS) predicted risk of mortality (PROM) calculator.

Results:

Compared to patients who underwent SAVR, patients who underwent TAVR were older (82 vs. 65 years; p < 0.001), had a lower ejection fraction (48% vs. 53%; p < 0.001), and had a higher STS PROM (11.9% vs. 4.6%; p < 0.001). In-hospital mortality rates for TAVR and SAVR were 3.5% and 4.1%, respectively (p = 0.60), a result that marginally favors (sic) TAVR after risk adjustment (adjusted odds ratio, 0.52; p = 0.06). In SAVR patients, worse preoperative renal function was associated with increased in-hospital mortality (p = 0.004), and with both hospital (p < 0.001) and intensive care unit (ICU) lengths of stay (p < 0.001). In contrast, worse renal function in TAVR patients was not associated with in-hospital mortality (p = 0.78), or with either hospital (p < 0.23) or ICU lengths of stay (p = 0.88).

Conclusions:

The authors concluded that worse renal function was associated with increased in-hospital mortality, hospital length of stay, and ICU length of stay in SAVR patients; but not in TAVR patients. They suggested that this unexpected finding might have clinical implications among patients with aortic stenosis and preoperative renal dysfunction.

Perspective:

This is a problematic paper, in part based on how it is written (data appear in the abstract but not the manuscript text, dynamic worsening of renal function is used instead of what was really worse renal function, and ‘p’ values >0.05 are taken to be representative of significant differences between groups). The clinical message also might be limited. Dramatically different, unmatched groups were compared in a retrospective review, and only acute outcomes were assessed. Implications of pre-existing renal dysfunction on decisions regarding TAVR and SAVR probably are best made using longer-term outcomes.

Keywords: Odds Ratio, Intensive Care Units, Renal Insufficiency, Hospital Mortality, Glomerular Filtration Rate, Regression Analysis, Length of Stay, Risk Adjustment


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