Does Impella Affect Predicted AKI Risk?

Study Shows a 78% Risk Decrease in Overall Incidence of Post-procedural AKI

Dr. Michael Flaherty presents a more contemporary analysis of acute kidney injury (AKI) in patients undergoing high-risk PCI with Impella® support. As interviewer Dr. Shon Chakrabarti notes, data from the PROTECT II randomized, controlled clinical trial revealed that the Impella arm of the study had more lesions treated and more atherectomy, and as a result, received more contrast than the IABP arm of the study. Yet patients in the Impella arm did not experience more AKI.

“We looked at the PROTECT II data and we saw that the prevalence of CKD was around 30%,” Dr. Flaherty explains, “however only 4% of those patients developed AKI.” Intrigued by these findings, Dr. Flaherty began looking deeper into acute kidney injury in patients undergoing high-risk PCI who had Impella support and those who were not supported with Impella, and in 2017 published a paper in Circulation Research in which he describes a significant reduction in the incidence AKI in patients supported with Impella (~5.2%) compared with unsupported patients (~28%).

Dr. Flaherty explains that these results led him to want to develop a renal protection risk stratification strategy that could answer the question, “Does Impella affect predicted AKI risk?” He describes how he applied the Mehran AKI risk-predicting scheme to a similar group of patients and compared their predicted risk for AKI with those that developed AKI. In 2019 he published his results of the Global cVAD Renal Protection Study in Catheterization and Cardiovascular Interventions.

“What we found,” Dr. Flaherty reports, “was that the AKI incidence relative to the Mehran risk score predicted AKI rates was significantly lower in those patients who underwent Impella assisted high-risk PCI.” The overall incidence of post-procedural AKI was 4.9% in patients supported with Impella compared with 21.9% predicted AKI incidence—a 78% risk decrease, despite severely reduced EF, anemia, diabetes, prolonged procedure time, and contrast volume. Dr. Flaherty explains that the AKI incidence did not correlate with baseline CKD severity. “As CKD severity increased, the risk of AKI also increased, but we didn’t see a significant increase in the development of acute kidney injury in those patients.” However, when controlling for clinical and procedural variables, worsening renal function was a predictor for AKI.

At the conclusion of the interview, Dr. Flaherty offers his expert opinion on the most likely mechanistic underpinning of the results indicating that Impella hemodynamic support protects the kidney. “We feel that probably it’s a reduction in stagnation of the contrast in the renal tubules,” he explains, with increasing cardiac output allowing for washout of the contrast and improved renal perfusion throughout the case. He notes that Dr. Navin Kapur is further investigating this mechanism.

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