Original ArticleFactors Contributing to Acute Kidney Injury and the Impact on Mortality in Patients Undergoing Transcatheter Aortic Valve Replacement
Introduction
Elderly patients with significant aortic stenosis have a poor prognosis without surgery to replace the valve [1]. However, they are often deemed too high risk for an operation because of frailty or significant comorbidities [1], [2], [3]. Transcatheter aortic valve replacement (TAVR) is an alternative to conventional open heart surgery in the treatment of severe symptomatic aortic stenosis in this patient group [4], [5], [6]. These patients are at an increased risk of complications, particularly acute kidney injury (AKI). The incidence of AKI in patients undergoing TAVR is reported to be as high as 41.7% [7] and post TAVR renal failure was listed as the most common complication at 30 days in the local SOURCE ANZ registry [8]. Acute kidney injury has been associated with increased length of hospital stay [9], [10], 30-day [11] and one-year mortality [12].
Iodinated contrast media (ICM) may adversely affect renal function, termed contrast-induced nephropathy (CIN) [13]. Iodinated contrast media causes cellular injury and death to renal tubular cells [14]. In patients undergoing TAVR, the relationship between AKI and ICM is not conclusive, with some studies indicating that ICM use impacts on AKI [15] and others reporting that there is no relationship [11], [12], [16], [17], [18], [19], [20]. It is suggested that the high incidence of AKI in this elderly group of patients is multi-factorial, with comorbidities such as age, hypertension [17], peripheral vascular disease (PVD) [7], [12] and chronic obstructive pulmonary disease (COPD) [11] being associated with a higher incidence of AKI. To date there are limited local data for AKI incidence and outcomes in patients undergoing TAVR in Australia. This study aimed to investigate AKI in an Australian TAVR centre and investigate how AKI is related to ICM usage, baseline patient characteristics and TAVR procedural data. This study had four aims:
- 1.
Determine the relationship between ICM volume and AKI in this cohort.
- 2.
Determine what risk factors or baseline characteristics are related to patients that suffer AKI during TAVR in this cohort.
- 3.
Determine any procedural factors that have not been previously reported that may predict AKI.
- 4.
Investigate the impact of AKI on hospital length of stay and early, mid and long term-mortality in this cohort.
Section snippets
Materials and Method
209 consecutive patients who underwent TAVR procedures between August 2008 and July 2013 were included. The study encompassed TAVR patients in whom either the CoreValve (Medtronic), Edwards Sapien valve (Edwards Lifesciences) or the Lotus Valve (Boston Scientific) were implanted. It excluded those who had a TAVR device implanted in pre-existing prosthetic aortic valves and those who had presented for repeat TAVR. It included patients who had TAVR devices implanted from the femoral artery, via
Results
Of the 209 patients in this cohort, 82 developed AKI (39%). Of these 82 patients, 65 had stage 1, nine had stage 2 and eight had stage 3 AKI (Figure 1).
Discussion
The 39% overall incidence of AKI in this cohort was higher than some of the literature, [16], [17], [18] but similar to the 41.7% seen in others [7]. This high incidence may be due to AKI being defined in this study with all three stages of the VARC 2 criteria included [21]. Only 17 (8%) of the 209 patient cohort suffered either stage 2 or 3 AKI and is consistent with the 8.3% occurrence quoted in another study observing AKI stages 2 and 3 [18]. The reason for the high overall incidence is
Conclusion
This study demonstrated that AKI is a common complication of TAVR and that the severity of AKI is important in determining mortality. Acute kidney injury does not appear to be dependent on ICM volume. Pre-existing chronic kidney disease, respiratory failure, previous stroke and blood tranfusion were highlighted as important predictors for AKI. Transcatheter aortic valve replacement device repositioning or retrieval was also identified as a new risk factor impacting on AKI.
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