A role for preventive measures
Preventive strategies to consider for higher-risk patients include limiting the administered volume of iodinated contrast media, increasing hydration, and avoiding nephrotoxic agents, Dr. Mehran said. The two new risk-assessment tools will “allow for better evaluation of PCI patients” when testing “innovative strategies and treatments” designed to help avoid contrast-associated AKI.
“The focus to date has been on measures to protect renal function from contrast media, based on indirect data,” Estelle C. Nijssen, MSc, and Joachim E. Wildberger, MD, wrote in an editorial that accompanied the published report. “The effect of prophylactic measures on longer-term averse outcomes is still unclear,” they noted. “Perhaps our focus should shift from contrast and renal function to the heart, the role of which has probably been undervalued in this setting,” wrote Ms. Nijssen, a researcher at Maastricht (The Netherlands) University, and Dr. Wildberger, professor and chairman of the department of radiology at Maastricht University.
The editorial’s authors noted that the two new risk scores have the advantage of relying on variables that are “readily available in clinical practice.” But they also noted several limitations, such as the model’s development from largely low-risk patients who had a low, roughly 30% prevalence of chronic kidney disease. During 9 full years studied, 2012-2020, the annual incidence of AKI showed a downward trend, with an incidence of just over 3% in 2020.
Dr. Mehran attributed this decline in AKI to “great work identifying high-risk patients” and using the prophylactic measures she cited. But even when occurring at relatively low incidence, “AKI is still an important complication that is associated with mortality post PCI,” she stressed.
Establishing a safe contrast dose
“The study is great, and helps reinforce the risk factors that are most important to consider when risk stratifying patients prior to PCI,” said Neal Yuan, MD, a cardiologist at the University of California, San Francisco, who has studied contrast-associated AKI in patients who undergo PCI. The report from Dr. Mehran also “confirms in a large cohort the association between contrast-associated AKI and death,” and describes “an easy method for calculating risk,” he said in an interview.
Dr. Yuan agreed on the need for external validation, and once adequately validated he called for incorporation of the risk score into EHRs. Another important issue for future study is “how much [AKI] risk is too much risk,” he said.
The risk factors identified in Dr. Mehran’s report “are some of the same ones identified in previous studies. Even though this was a more contemporary dataset, there is not a ton of new [findings]; it mainly strengthens findings from prior studies.”
Results published by Dr. Yuan and his associates in 2020 used data from more than 20,000 U.S. patients who underwent PCI to try to identify a generally safe upper limit for the dose of iodinated contrast.
The main purpose for performing AKI risk stratification on PCI patients is to “identify high-risk patients and use preventive strategies when treating these patients.” Current AKI preventive strategies “mainly fall into intravascular volume expansion, and reduced contrast.” What’s less clear is “how to operationalize reduced contrast,” he said.
The report by Dr. Yuan showed that “about 10% of PCI patients were at very high risk” for contrast-associated AKI “no matter what is done.” In contrast, about two-thirds of PCI patients “could receive lots of contrast and still be very unlikely to develop AKI,” Dr. Yuan said.
He voiced some skepticism about the willingness of many clinicians to routinely use a formal risk score to assess their patients scheduled for PCI.
Most operators “approximate AKI risk based on variables such as age and creatinine level, but few take time to put the variables into a calculator to get an exact risk number.” In a “small survey” he ran, he found that these rough approximations often ignore important risk factors like hemoglobin level. This inertia by clinicians against routinely using a risk score could be addressed, at least in part, by integrating the risk score into an EHR for automatic calculation, Dr. Yuan suggested.
Dr. Mehran noted that the risk score that she introduced in 2004 is used “in many EHRs to identify high-risk patients.”
The current study received no commercial or external funding. Dr. Mehran has been a consultant to Boston Scientific, Cine-Med Research, CIRM, and Janssen, and she holds equity in Applied Therapeutics, Elixir Medical, and STEL. Dr. Wildberger had no relevant disclosures. Ms. Nijssen and Dr. Yuan had no disclosures.