The prognostic relevance of direct contrast toxicity in patients treated with transcatheter aortic valve implantation (TAVI) remains unclear because of the confounding hemodynamic effect of acute left ventricular ejection fraction (LVEF) impairment on kidney function estimation. In addition, different definitions of contrast-induced acute kidney injury (CI-AKI) may have different prognostic stratification potential. In the present study, 240 consecutive patients who underwent TAVI were prospectively enrolled. CI-AKI was defined (1) according to the postprocedural creatinine increase of ≥0.3 mg/dl or (2) according to the postprocedural decrease of the creatinine clearance of at least 25%. Primary end point of the study was 1-year all-cause mortality. At a mean follow-up of 1.7 ± 1.4 years, all-cause mortality was significantly higher in the CI-AKI patient group, using both CI-AKI definitions (for (1) and (2) p = 0.025 and p <0.001, respectively). In the Cox regression multivariate analysis, CI-AKI was an independent predictor of mortality (hazard ratio 2.244, 95% CI 1.064 to 4.732, p = 0.034), along with LVEF (hazard ratio 0.974, 95% CI 0.946 to 0.993, p = 0.012). Although LVEF and creatinine values at admission were not significantly associated with CI-AKI, their interaction term significantly defined CI-AKI (p = 0.033). The prognostic accuracy of definition (2) was higher (area under the curve 0.704; p <0.001) as with respect to definition (1) (area under the curve 0.602; p = 0.037) for the primary end point of 1-year mortality. In conclusion, in a nonselected patient population who underwent TAVI, CI-AKI was confirmed as an independent predictor of clinical outcome. Only the interaction between LVEF and baseline creatinine values was found to determine CI-AKI. Definition of CI-AKI based to creatinine clearance values had higher prognostic accuracy in comparison with the CI-AKI definition based on creatinine absolute value changes.
Contrast-induced acute kidney injury (CI-AKI) is associated with worse outcome in patients who underwent transcatheter aortic valve implantation (TAVI). However, recent data suggested that an increase in values of creatinine could be the result of hemodynamic compromise because of an acute impairment of cardiac pump function after an extended myocardial infarction, rather than the direct impact of contrast-induced kidney injury. The Valve Academic Research Consortium (VARC) defines CI-AKI in patients who underwent TAVI as (1) a postprocedural increase in absolute creatinine values of ≥0.3 mg/dl or (2) a postprocedural decrease of the creatinine clearance of at least 25%. The potential differences in prognostic accuracy between these 2 definitions have not been previously assessed. The present study (1) examines whether in patients who underwent TAVI and without acute systolic function decrease, CI-AKI maintains its negative prognostic stratification potential and (2) assesses the potential differences in prognostic accuracy between the 2 earlier mentioned definitions of CI-AKI in a real-world retrospective population of patients who underwent TAVI.
Methods
From December 2009 to January 2014, 240 consecutive patients with severe aortic stenosis who underwent TAVI were enrolled at the Contilia Heart and Vascular Center, Essen, Germany. Baseline demographics, procedural data, and clinical outcomes were prospectively collected, whereas the analysis was performed retrospectively.
All potential TAVI candidates were assessed by a local heart team composed by interventional cardiologists and cardiac surgeons who determined the indication of the patient for TAVI. All candidates underwent a pre-interventional screening process to determine eligibility. The latter included transthoracic and transesophageal echocardiography to confirm diagnosis, multislice computer tomography to assess aortic and aortic valve dimensions and morphology, grade and distribution of calcifications, annulus dimension in a multiplanar reconstruction measuring from hinge point to hinge point and the access, and invasive cardiac evaluation with coronary angiogram, supra-aortic angiogram, and left ventriculography. Baseline surgical risk was estimated using logistic EuroSCORE. Vascular access was evaluated using multislice computer tomography of the abdominal aorta and the iliac and femoral vessels. Severe aortic valve stenoses were defined by echocardiographic criteria including a mean gradient >40 mm Hg or peak jet velocity >4.0 m/s and aortic valve area ≤0.8 cm 2 or aortic valve area index ≤0.5 cm 2 /m 2 .
The choice of the valve type was based on operator preference in all cases. Overall patients were analyzed for potential interaction between left ventricular ejection fraction (LVEF) and renal function. All patients provided written informed consent for the TAVI procedure and data collection. This study was performed in accordance with the guidelines set by the Declaration of Helsinki and with the local legal requirements. No extramural funding was used to support the study. The authors wrote the manuscript and are responsible for the completeness and accuracy of data gathering and analysis.
For the primary end point analyses, 2 different definitions of CI-AKI have been used: definition (1)—postprocedural creatinine increase of ≥0.3 mg/dl, and definition (2)—postprocedural decrease of the creatinine clearance of at least 25% (calculated using the Cockcroft-Gault formula). Serum creatinine concentration was measured at the time of admission (just before TAVI), every day for the following 3 days, and at hospital discharge. Chronic kidney disease (CKD) was defined as a baseline serum creatinine of >1.5 mg/dl or an estimated glomerular filtration rate of 60 ml/min/1.73 m 2 (Levey-modified MDRD formula). Patients with CKD were not excluded from the present study, regardless of the CKD degree. Clinical follow-up was performed using hospital records and telephone interviews. The primary end point of our study was all-cause mortality at 1 year of clinical follow-up.
Continuous variables are expressed as mean ± SD or median (interquartile range). Categorical variables are reported as frequencies and percentages. Normal distribution was assessed by the Kolmogorov-Smirnov test. Student’s t test or Mann-Whitney test were used to compare continuous variables, as appropriate. Comparisons between categorical variables were evaluated using 2-tailed Fisher’s exact test or Pearson’s chi-square test, as appropriate. In the global population of 240 patients, a binary logistic regression analysis was performed with respect to the end point CI-AKI. An interaction term was constructed, using the centered values of 2 continuous variables, LVEF and eGFR, respectively, and adjusted linear regression analysis was performed to assess statistical significance. Survival curves were constructed using the Kaplan-Meier method. The Cox multivariate regression analysis was performed twice, in a stepwise manner, and using each time a different definition of CI-AKI, adjusted for all variables with p <0.05 at the univariate Cox regression analysis. Comparative analysis between the 2 CI-AKI definitions for the accuracy on predicting 1-year mortality were performed with estimations of under the receiver-operating characteristic curve areas. The results expressed as hazard ratios (HRs) and 95% confidence intervals (95% CIs). All p values were 2 tailed. Analyses were done with SPSS software, version 17.0 (SPSS, Chicago, Illinois).
Results
Baseline clinical and procedural characteristics of the global population (n = 240) are listed in Tables 1 and 2 , respectively. The logistic EuroSCORE values were high at 23.8 ± 11.3%, confirming that our patient population reflects routine clinical practice performed on elderly, high-risk patients. The transfemoral approach was almost systematically used (91.3% of cases).
| Variable | Overall (n = 240) |
|---|---|
| Age (years) | 82.6 ± 6.0 |
| Man | 93 (38.8%) |
| Body-mass index (kg/m 2 ) | 26.3 ± 4.6 |
| Hypertension | 235 (97.9%) |
| Diabetes mellitus | 86 (35.8%) |
| Hypercholesterolemia | 204 (85.0%) |
| Coronary artery disease | 122 (50.8%) |
| Prior percutaneous coronary intervention | 82 (34.2%) |
| Prior coronary artery bypass graft | 42 (17.5%) |
| Cerebrovascular disease | 25 (10.4%) |
| Chronic obstructive pulmonary disease | 45 (18.8%) |
| Peripheral vascular disease | 26 (10.8%) |
| New York Heart Association functional class III-IV | 39 (16.3%) |
| Prior pacemaker | 22 (9.2%) |
| Atrial fibrillation | 79 (32.9%) |
| Logistic EuroSCORE | 23.8 ± 11.3 |
| Left ventricular ejection fraction (%) | 49.3 ± 13.5 |
| Left ventricular ejection fraction ≤ 30% | 35 (14.6%) |
| Chronic renal insufficiency ∗ | 65 (27.1%) |
| Plasma creatinine (mg/dl) | 1.31 ± 1.07 |
| Glomerular filtration rate (mL/min/1.73 m 2 ) | 55.8 ± 21.8 |
| Mean transvalvular gradient (mmHg) | 45.2 ± 14.0 |
| Aortic valve area (cm 2 ) | 0.72 ± 0.19 |
| Aortic annulus mean diameter by multi-slice computed tomography (mm) | 23.0 ± 2.2 |
∗ Defined as a pre-procedural glomerular filtration rate < 60 mL/min/1.73 m 2 .
| Variable | Overall (n=240) |
|---|---|
| Bioprosthesis size (mm) | 27.5 ± 1.9 |
| Bioprosthesis type | |
| • Edwards Sapien XT | 173 (72.1%) |
| • Medtronic Corevalve | 47 (19.6%) |
| • Direct Flow Medical | 20 (8.3%) |
| Access | |
| • Transfemoral | 219 (91.3%) |
| • Transapical | 31 (8.7%) |
| Contrast dose (ml) | 189.4 ± 75.3 |
| Peak-to-peak gradient pre-procedural (mmHg) | 75.5 ± 28.6 |
| Peak-to-peak gradient post-procedural (mmHg) | 6.1 ± 6.0 |
| Reduction of peak-to-peak gradient (mmHg) | 66.4 ± 11.2 |
| Aortic regurgitation after initial implantation | |
| • Mild/trace | 214 (89.2%) |
| • Moderate | 23 (9.5%) |
| • Severe | 3 (1.3%) |
Short-term (30 days) clinical outcome is listed in Table 3 . Overall mortality rate was 1.7%. Five patients had a stroke (2.0%), whereas 67 patients underwent a new pacemaker implantation (27.9%) because of persistent advanced atrioventricular block after valve implantation.
| Variable | Overall (n = 240) |
|---|---|
| All-cause mortality | 14 (1.7%) |
| Stroke | 5 (2.0%) |
| Pacemaker implantation | 67 (27.9%) |
| Major bleeding | 25 (10.4%) |
| Major vascular complications | 77 (32.1%) |
| Sepsis | 37 (15.4%) |
| Coronary obstruction | 1 (0.4%) |
| Contrast-induced acute kidney injury | |
| • Definition (1) ∗ | 44 (18.3%) |
| • Definition (2) † | 47 (19.6%) |
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