Prior Renal Impairment, Low Body Weight Predispose to Acute Kidney Injury After TAVR

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Besides baseline renal impairment, the strongest predictor of postprocedural acute kidney injury (AKI) in elderly, comorbid patients undergoing transcatheter aortic valve replacement (TAVR) is low body mass index (BMI), according to an observational study published online July 14, 2014, ahead of print in Catheterization and Cardiovascular Interventions. Patients who experience AKI after TAVR have increased risk of short- and long-term mortality and cardiovascular events. 

Clinicians should factor individual risk of AKI into evaluation for TAVR and potentially optimize the procedure and closely monitor those who experience deterioration in renal function, the authors suggest. 

Methods
Renate B. Schnabel, MD, MSc, and colleagues at University Heart Center (Hamburg, Germany), prospectively gathered data from 458 consecutive patients who underwent TAVR for severe aortic stenosis at their institution beginning in 2008. Mean age was 80.6 years, and 52.5% were women. Bioprosthetic devices included the Edwards Sapien (Edwards Lifesciences; Irvine, CA; n = 338), CoreValve (Medtronic; Minneapolis, MN; n = 63), Acurate TA (Symetis; Lausanne, Switzerland; n = 19), and JenaValve (JenaValve; Munich, Germany; n = 38). The procedure was performed via transapical access in 57.2% of patients.
Estimated glomerular filtration rate (eGFR) was assessed at baseline (mean 56.7 mL/min/1.73m2), during the 72 hours after TAVR, and at discharge. Patients with impaired baseline renal function (eGFR < 60 mL/min/m2) or otherwise at increased risk of AKI received balanced IV volume expansion with isotonic sodium chloride. 


The 30-day rate of MACE (MI and stroke) was 7.4%. Over a median follow-up of 350 days, 142 patients (31%) died. These individuals tended to be older and have more cardiovascular comorbidities; they also had a lower baseline eGFR. 

Acute renal failure occurred in 29.8% patients who died compared with 11.7% of survivors. Those with acute failure also spent more days in the hospital than those without the condition (10 vs 8 days). 

Baseline eGFR, Low BMI Emerge as Predictors  

Overall, 55.2% of patients showed a decrease in eGFR within 72 hours of TAVR. In multivariable regression analysis, the strongest predictors of renal deterioration were lower baseline eGFR (P < .0001) and lower BMI (P = .033).  

Other contributors were:

  • Procedure time (P = .012)
  • Major and life-threatening bleeding (P < .0001)
  • Number of erythrocyte concentrates administered within 24 hours after the procedure (P < .0001)
  • Major access site complications (P < .0001)

Predictors of change in eGFR from baseline to hospital discharge were similar. 

In multivariable models adjusted for age and sex and for clinical factors, nadir eGFR within 72 hours, decline in eGFR from baseline at 72 hours, and acute kidney failure were associated with 1-year mortality (table 1). The same predictors held true for 30-day mortality.

Table 1. Renal Predictors of 1-Year Mortality

 

Adjusted OR

95% CIa

Nadir eGFR ≤ 72 Hrs

    Adjusted for Age and Sex

    Adjusted for Clinical Factors

 

0.98

0.98

 

0.97-0.98

0.97-0.99

Change in eGFR from Baseline at 72 Hrs

     Adjusted for Age and Sex

     Adjusted for Clinical Factors

 

0.97

0.97

 

0.95-0.98

0.96-0.98

Acute Kidney Failure

     Adjusted for Age and Sex

     Adjusted for Clinical Factors

 

3.69

3.73

 

2.12-6.39

1.93-7.16

a All P < .0001. 

In addition, both eGFR at 72 hours and change in eGFR within 72 hours increased the predictive power of the EuroScore, with the C-statistic rising from 0.60 to 0.68 (P = .0048) and 0.66 (P = .021), respectively). 

There was no clear difference in long-term outcome between individuals whose deterioration in acute renal function at 72 hours persisted and those whose decline recovered by discharge. Patients with eGFR close to baseline values at discharge tended to have better survival at 30 days, but any advantage was lost at 1 year. 

No difference by prosthetic valve type was observed. 

Potential Measures to Reduce Risk

As in previous series, deterioration in renal function after TAVR was common, with 16% of patients in the current study experiencing acute kidney failure, the authors observe.

Since the need for red blood cell transfusion is known to correlate with renal impairment in both surgical and percutaneous aortic valve replacement, “all precautions should be taken to avoid unnecessary blood loss,” they advise. 

The study also demonstrated that the degree of change in postprocedural eGFR matters, underscoring the need for serial eGFR measurement to identify the nadir of renal function, which usually occurs more than 24 hours after the procedure, Dr. Schnabel and colleagues say. Similarly, the fact that change in eGFR from baseline and lowest eGFR at 72 hours increase the predictive accuracy of the EuroScore emphasizes the importance of renal function monitoring, they add. 

Renal impairment and AKI “need to be taken into account when evaluating patients who are planned for [TAVR],” the authors conclude, acknowledging that their study was hindered by few events and lack of information on concomitant medication use. “Future research needs to show whether close monitoring of renal function and targeted intervention can improve outcome.”

 


Source: 
Schnabel RB, Seiffert M, Wilde S, et al. Kidney injury and mortality after transcatheter aortic valve implantation in a routine clinical cohort. Catheter Cardiovasc Interv. 2014;Epub ahead of print.

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Disclosures
  • Dr. Schnabel reports no relevant conflicts of interest.

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