AKI and Cardiovascular Events After PCI by Race, Diabetes, and Kidney Function

Patients undergoing percutaneous coronary intervention (PCI) may experience acute kidney injury (AKI) and face increased cardiovascular risk following the procedure. Compared with White patients, there is a disproportionate rate of AKI among Black patients. Black patients also have an increased overall risk of cardiovascular events compared with the general population. Further, diabetes and reduced kidney function are risk factors for AKI and are independently associated with increased cardiovascular risk in both PCI and non-PCI populations.

According to Joseph Lunyera, MBChB, MSc, and colleagues, there are few data available on the synergistic impact of AKI and AKI predisposition by race, diabetes, or reduced kidney function on the cardiovascular risk after PCI. The researchers conducted an observational cohort study to test the hypothesis that there would be a differential association between AKI and increased cardiovascular risk at 1 year after PCI, with a more pronounced association in Black patients than in White patients or those of other racial groups, and among patients with diabetes or reduced kidney function than in patients without those AKI risk factors.

The study utilized detailed clinical data in the Duke Databank for Cardiovascular Disease. The database includes all patients who underwent cardiac catheterization at Duke University Medical Center in Durham, North Carolina, between 1974 and 2014. Patients who underwent PCI at Duke between January 1, 2003, and December 31, 2013, were included in the study.

The study exposure was AKI, defined as a ≥1.5-fold relative elevation in serum creatinine within 7 days from a reference value ascertained 30 days prior to PCI, or a 0.3 mg/dL increase from the reference value within 48 hours. The primary study outcome of interest was a composite of all-cause death, myocardial infarction, stroke, or revascularization during the first year after PCI. Secondary outcomes were each individual component of the composite cardiovascular outcome.

Cox regression models adjusted for potential confounders and with interaction terms between AKI and race, diabetes, or baseline estimated glomerular filtration rate (eGFR) were used to examine the association between AKI and increased cardiovascular risk at 1 year after PCI.

The analytic cohort included 9422 unique patients who underwent an index PCI procedure during the study period. Most patients self-identified as White (75%, n=7084), 20% self-identified as Black (n=1864), and 5% self-identified as Native American or other (n=484). Median age was 63 years, and median household income was $44,612.

Overall, 32% of PCI procedures (n=3027) were urgent/emergent. Among patients with AKI, 43% of the procedures were urgent/emergent, and among patients without AKI, 31% were urgent/emergent. Most patients had a previous diagnosis of hypertension (70% overall, n=6607). Median baseline eGFR was 74 mL/min/1.73 m², and 30% of the cohort (n=2804) had diabetes. Only 1.7% (n=179) had diabetes with end organ damage.

Nine percent of the cohort (n=865) developed AKI within 7 days after PCI. The incidence of AKI was highest among Black patients (14%, n=258) relative to White patients (8%, n=561) and Native American/other patients (10%, n=46).

Overall, 21% of patients (n=2017) met the definition of the primary composite outcome at 1 year after PCI. For secondary outcomes, the rates were 6% (n=579) for death, 8% (n=719) for myocardial infarction, 3% (n=26) for stroke, and 11% (n=1031) for revascularization. The event rate for the composite outcome was 2-fold higher for patients with AKI compared with those without AKI (41% vs 20%), which was driven by death (21% vs 5%) and myocardial infarction (17% vs 7%).

AKI, compared with no AKI, was associated with greater risk for the primary composite outcome (adjusted hazard ratio [aHR], 1.94; 95% CI, 1.71-2.20). There was also an association between AKI and greater risks for death, myocardial infarction, and stroke. There was no association between AKI and revascularization.

There were significant differences by race in risks for the primary composite outcome (P=.04): compared with White patients, risk was greater in Black patients (aHR, 1.09; 95% CI, 0.97-1.22) but lower in Native American/other patients (aHR, 0.81; 95% CI, 0.65-1.01). The difference in risk between White and Black patients was driven by greater myocardial infarction risk in Black versus White patients (aHR, 1.43; 95% CI, 1.19-1.71; P<.001). There were no significant differences by race in risks for the other individual components of the composite outcome.

There was an association between diabetes without reported end organ dysfunction compared with no diabetes, and a greater risk for the primary composite outcome (aHR, 1.18; 95% CI, 1.07-1.31). For diabetes with reported end organ dysfunction, the risk was even greater, although the subgroup was small. Reduced baseline eGFR was also associated with graded, higher risk for the primary outcome (P for trend <.001). With the exception of vascularization, the risks were evident for all secondary outcomes.

There was no significant modification to the association between AKI and risk for the composite outcome based on baseline eGFR. However, the associations of AKI versus no AKI with increased risk for all-cause death were significantly greater in the higher eGFR categories.

With White patients with no AKI as the reference, the risk for the composite outcome was highest in Black patients with AKI (HR, 2.27; 95% CI, 1.83-2.82), followed by White patients with AKI (HR, 1.87; 95% CI, 1.58-2.21). The risk was least in patients of other races with AKI (HR, 1.48; 95% CI, 0.88-2.48). The results were similar with individual components of the composite outcome, with the exception of revascularization.

Study limitations cited by  the authors included the observational nature of the study, the single-center design, and the possibility that the study was underpowered.

In conclusion, the researchers said, “AKI compared with no AKI conferred greater risks for a composite cardiovascualr outcome comprising, death, myocardial infarction, stroke, and revascularization at 1 year after PCI, but this AKI-associated risk did not differ significantly by race, diabetes, or baseline kidney function. Despite the lack of differential AKI-associated risk by race, Black patients with AKI had qualitatively greater cardiovascular risk at 1 year after PCI than White patients with AKI. Thus, AKI prevention interventions to offset cardiovascualr risk after PCI should be prioritized in all patients undergoing the procedure.”

Takeaway Points

1. Researchers conducted an observational cohort study to test the hypothesis that acute kidney injury (AKI) would be differently associated with increased cardiovascular risk at 1 year after percutaneous coronary intervention(PCI), with a more pronounced association in Black patients than in White patients.
2. AKI was associated with a nearly 2-fold higher risk of a composite outcome of all-cause death, myocardial infarction, stroke, or revascularization, compared with no AKI.
3. Black race and severely reduced estimated glomerular filtration rate, but not diabetes, had a cumulative impact with AKI on the risk for the composite outcome.

Source: American Journal of Kidney Diseases