ABC | Volume 113, Nº6, December 2019

Original Article Calça et al. Aortic valve repair and kidney function Arq Bras Cardiol. 2019; 113(6):1104-1111 Table 5 – Repeated Measures ANOVA: pairwise comparisons (Group 2) (I) eGFR (J) eGFR Mean Difference (I-J) Std. Error Sig. † 95% Confidence Interval for Difference † Lower Bound Upper Bound eGFR pre-TAVI eGFR 1 month after TAVI -4.716 2.019 0.079 -9.728 0.295 eGFR 1 year after TAVI -7.201* 2.007 0.002 -12.184 -2.219 eGFR 1 month after TAVI eGFR pre-TAVI 4.716 2.019 0.071 -0.295 9.728 eGFR 1 year after TAVI -2.485 2.178 0.779 -7.893 2.923 eGFR 1 year after TAVI eGFR pre-TAVI 7.201* 2.007 0.002 2.219 12.184 eGFR 1 month after TAVI 2.485 2.178 0.779 -2.923 7.893 *The mean difference is significant at the 0.05 level. † Adjusted for multiple comparisons: Bonferroni. eGFR: estimated glomerular filtration rate; TAVI: transcatheter aortic valve implantation. Table 6 – Repeated Measures ANOVA: pairwise comparisons (Group 3) (I) eGFR (J) eGFR Mean Difference (I-J) Std. Error Sig. † 95% Confidence Interval for Difference † Lower Bound Upper Bound eGFR pre-TAVI eGFR 1 month after TAVI -10.453 4.670 0.119 -22.938 2.031 eGFR 1 year after TAVI -13.923* 4.944 0.037 -27.138 -0.708 eGFR 1 month after TAVI eGFR pre-TAVI 10.453 4.670 0.119 -2.031 22.938 eGFR 1 year after TAVI -3.470 2.658 0.631 -10.576 3.636 eGFR 1 year after TAVI eGFR pre-TAVI 13.923* 4.944 0.037 0.708 27.138 eGFR 1 month after TAVI 3.470 2.658 0.631 -3.636 10.576 *The mean difference is significant at the 0.05 level. † Adjusted for multiple comparisons: Bonferroni. eGFR: estimated glomerular filtration rate; TAVI: transcatheter aortic valve implantation. and dimeric structure opposed to monomeric low-osmolar contrast media. 25 Despite the many years of experience in the use of iodine contrast, the exact pathogenesis of contrast‑induced nephropathy (CIN) remains unknown. The causes might include the osmotic effect of contrast media on the kidneys, the increased levels of vasoconstrictive factors, such as adenosine or endothelin, the reduced levels of vasodilators, such as nitric oxide or prostacyclin, and the toxic effect of contrast molecules on renal tubules. 25 According to the American College of Radiology guidelines, iso-osmolar iodixanol has no evident superiority over low‑osmolar contrast with respect to the incidence of CIN. 26 Regardless, the difference in the contrast administrated may be one of the factors contributing to the poorer results in patients from Group 1 , although there are not enough data to prove this supposition, namely whether these patients had AKI after the procedure. Another hypothesis that could explain the kidney function variation in patients with CKD G1-2 is that, prior to the aortic valve repair, they could not tolerate the angiotensin-converting enzyme inhibitor (ACEi) or angiotensin II receptor antagonists (ARA-II), and as such, the therapeutic could be optimized after the procedure, thus explaining the GFR variation. We found an incidence of new dialyses of 2.4% (five patients) after a year of follow-up in all categories of CKD without statistical difference between them. A recent study in this field showed a difference in new-dialysis patients according to their CKD stage, with an incidence of 1.2%, 3.74%, 14.6%, and 60.1% in CKD 1-2, CKD 3, CKD 4, and CKD 5, respectively. 18 Given the low incidence of patients who started dialysis in the follow-up period after TAVI, drawing statistically relevant conclusions would not be accurate; nevertheless, we believe that some of these results stand out: (i) the mean age of these patients was 80 ± 5.96 years, similar to the mean age of all the analyzed population (81.8 ± 7.5 years); (ii) almost all patients died (4 out of 5); (iii) all patients had chronic heart failure, which probably contributed to the outcome. The main limitations of this study concern its retrospective and observational nature. The use of patient charts for data collection is also a limitation, as some data might be missing or incorrectly coded. In addition, a significant number of patients were excluded, which could introduce a systematic bias toward the patients included in the study. Also, sCreat fluctuates often day-to-day, as it is influenced by numerous factors, such as hydration state, medication, or comorbidities. These variations in sCreat significantly affect the estimated kidney function. The present study also has some limitations regarding the patients’ follow-up: short follow-up period (one year); the decline in kidney function with age may be a confounding factor for the true benefit of aortic valve 1109