Study population

This single center, observational study was performed in patients who underwent PCI between September 2020 and December 2022 with the DyeVert Power XT system (case group) and in patients who underwent PCI during a similar period without the use of the device (control group).

Inclusion criteria for both groups were as follows: chronic kidney disease (CKD) [estimated glomerular filtration rate (eGFR) < 60 mL/min/m²] and/or need for a complex PCI with the likelihood of receiving a large amount of CM; previous coronary artery bypass graft (CABG); chronic total occlusion (CTO) (complete blockage of a coronary artery lasting at least 3 months); bifurcation; and left main and/or multivessel disease (at least 2 vessels involved).

The exclusion criterion for both groups was the presence of end-stage kidney failure on dialysis treatment. We collected laboratory, instrumental, clinical, and procedural variables in the case and control groups. Definitions of all these variables are reported in table 1, table 2, table 3, and table 4. For the variables included in the Mehran score, we used the same descriptions as those used in the score. eGFR was calculated by the Modification of Diet in Renal Disease (MDRD) 4-variable equation, left ventricular EF by 2-dimensional echocardiography during hospitalization and before arrival in the catheterization laboratory, and the risk of any post-PCI CIN by the Mehran score. Bifurcation/left main treatment (with single/double stent) consisted of the proximal optimization technique (POT) with kissing balloon inflation and eventually re-POT in all cases. Total CMV represents the volume that would have been delivered if DyeVert had not been used, ie, the sum of CMV delivered to patients and the CMV saved by DyeVert. CM injection flow was 4 and 3 mL/sec for the left and right coronary artery, respectively.

Image quality was evaluated by operators during the procedures. When quality was inadequate, exclusion of the device from the CM line was allowed for the shortest possible time.

AKI was defined as a rise in the concentration of serum creatinine ≥ 0.3 mg/dL within 48 hours after CM administration from the baseline value obtained before CM injection; further measurements after 48 hours were collected in patients with worsening kidney function; for its prevention, all patients received hydration with sodium chloride 0.9% intravenous solution at a rate of 1 or 0.5 mL/kg/h, as appropriate. The severity of AKI was defined according to Kidney Disease Improving Global Outcome (KDIGO) stages.

The research reported was performed in accordance with recommendations for clinical investigation (Declaration of Helsinki of the World Medical Association, October 2013) and was approved by an ethics committee. We declare that relevant informed consent was obtained from all participants and is available.

Objectives

In the case group, we evaluated the following: a) the amount of CMV saved using DyeVert and image quality; b) the rate and severity of CI-AKI and the rate of in-hospital all-cause death; c) laboratory, instrumental, clinical, and procedural differences in the 2 subgroups defined on the basis of the incidence of AKI; and d) independent predictors of CI-AKI.

In the overall population of the case and control groups, we performed propensity score matching (PSM) to obtain a group of patients with a sufficiently good balance (matched group), in which we evaluated the following: a) differences in CMV, and b) rate and severity of CI-AKI.

Statistical analysis

Categorical variables are expressed as the number and percentage of patients. Continuous parametric data are reported as the mean ± standard deviation and continuous nonparametric data as the median [lower and upper quartile]; for assessment of normality, the Kolmogorov test was used. Patients' categorical variables were compared using the chi-squared test (with Yates' correction for continuity in the case of variables with only 2 categories) or the Fisher exact test, as appropriate. The unpaired t-test was used for continuous parametric variables and the Mann-Whitney U-test for continuous nonparametric variables; the same tests were used in the matched group. On univariate analysis, significance was defined as P < .05. To establish the independent predictors of AKI, we performed multivariable logistic regression analysis. Variables were selected according to significance in the univariate analysis. The chosen method was stepwise backward regression with a maximum of 20 iterations. Multicollinearity was assessed with tolerance and variance inflation factor (VIF) values. Receiver operating characteristic (ROC) curves were used to establish the optimal cutoffs of independent predictors for the diagnosis of AKI. To perform PSM, the algorithm used was nearest neighbor matching 1:1 with a caliper size of ± 0.2. Statistical analyses were performed using SPSS for Windows, release 29, with R 4.2 implementation to perform PSM.

Analysis in the case group

A total of 101 patients (median age 74 [68-80] years, male sex 79.2%, CKD 72.3%) underwent PCI with the use of the DyeVert Power XT system.

In the overall population of the case group, mean hematocrit (HCT) was 38.6 ± 4.9 %, median EF was 50% [35%-55%], and mean Mehran score was 11 ± 5 points.

Congestive heart failure (CHF) was present in 37 patients (36.6%), Mehran CI-AKI very high-risk class was present in 17 patients (16.8%) and Mehran CI-AKI low-risk class was present in 24 patients (23.8%) (table 1).

We enrolled 20 patients (19.8%) with previous CABG, 12 (11.9%) with CTO, 34 (33.7%) with bifurcations, 25 (24.8%) with left main coronary artery disease, and 44 (43.6%) with multivessel disease. Delivered CM was 242 (189-300) mL, total CM was 355 ± 110 mL, and saved CM was 114 ± 42 mL, with an average of 32% of the total CMV (table 2). In almost all patients (n = 96, 95% of patients), image quality was adequate, while the device was excluded to make it adequate for the shortest possible time in 5 patients. Without these exclusions, saved CMV would have been slightly higher and with trivial changes with regard to the comparison with controls: 33% of the total, a value derived from patients without exclusions (n = 96).

A total of 14 (13.9%) patients developed CI-AKI (AKI-KDIGO 1, 2, 3: 6.9%, 3%, and 4%, respectively). The results of the univariate analysis for the overall population and according to the incidence of CI-AKI in the case group are reported in table 1, table 2, and figure 1.

Figure 1. In-hospital all-cause mortality rate according to onset of CI-AKI in the case group. CI-AKI, contrast induced-acute kidney injury. 

Compared with patients not developing CI-AKI, those in the CI-AKI subgroup had lower HCT values (35.5 ± 4.8 vs 39.1 ± 4.8; P = .01), lower EF values (30 [28-36] vs 50 [40-55]; P < .001) and higher Mehran score values (15 ± 4 vs 10 ± 5; P < .001).

In addition, the first patients more frequently had CHF [12 (85.7%) vs 25 (28.7%); P <.001] and Mehran CI-AKI very high-risk class (7 [50%] vs 10 [11.5%]; P =.002) and less frequently had Mehran CI-AKI low-risk class (0 [0%] vs 24 [27.6%]; P = .04).

No significant differences were found in the remaining laboratory, instrumental, or clinical features or the procedural variables between the 2 subgroups; in particular, CM was slightly higher in CI-AKI patients: 258 [195-277] vs 240 [188-306] mL, total 356 ± 106 vs 354 ± 79 mL; P = .95 for both variables delivered. In the multivariate analyses, independent predictors of CI-AKI were HCT (OR, 0.86, 95%CI, 0.74-0.99; P = .04) and EF (OR, 0.88, 95%CI, 0.82-0.95; P = .001); the percentage accuracy in classification of the model was 88%, while tolerance and VIF values (0.99 and 1.01, respectively) showed no multicollinearity. The HCT ROC curve showed the following values: area under curve (AUC) 0.71 with 95%CI 0.56-0.87; P = .01; a cutoff of 36.3% had the best sensitivity (72%) and specificity (71%) for the outcome (figure 2). The EF ROC curve showed the following values: AUC 0.83 with 95%CI 0.72-0.94; P = .001; a cutoff of 37% had the best sensitivity (82%) and specificity (79%) (figure 2); therefore, our best predictor was EF < 40%.

Figure 2. Receiver operating characteristic curves showing the diagnostic ability of HCT and EF for the diagnosis of CI-AKI in the case group. 

There were 4 in-hospital all-cause deaths overall, 2 deaths in each subgroup (CI-AKI and no-CI-AKI subgroups), as shown in figure 1.

Analysis in the matched group

After the matching process, 49 patients remained in the control (no DyeVert) and case (DyeVert) groups with no significant imbalance (ie, standardized mean differences < ± 0.25), as reported in table 3 and table 4. As shown in figure 3, delivered CM was slightly lower in the DyeVert group than in the no-DyeVert group, with no significant difference (252 ± 80 vs 267 ± 101 mL; P = .42), while total CM was significantly higher in the DyeVert group (354 ± 110 vs 267 ± 101 mL; P < .001). The CI-AKI rate was slightly lower in the case group than in the control group (14.3% vs 16.3%; P = .99) with slightly more advanced stages of AKI in controls (table 1 of the supplementary data), without significance.

Figure 3. Contrast medium in cases and controls in the matched group. 

Study limitations

Our study has some limitations. First, the sample size was relatively small. Second, the study design was single center, observational and retrospective, although we performed PSM to reduce potential confounding bias. Third, we excluded patients not meeting the inclusion criteria, as they were usually at low risk of CI-AKI. Therefore, our results should be generalized with caution, since the analyzed patients may be not representative of the general population. In this work the variable of sex has not been taken into account in accordance with the SAGER guidelines.