Registry Suggests Link Between PCI Access Route, Kidney Damage

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Percutaneous coronary intervention (PCI) is associated with lower risk of acute kidney injury (AKI) when performed via radial rather than femoral access, according to a study published online February 25, 2014, ahead of print in Circulation: Cardiovascular Interventions. However, researchers caution that the observational findings, from a Michigan registry, should be considered hypothesis-generating only.

A team led by Hitinder S. Gurm, MD, of the University of Michigan (Ann Arbor, MI), analyzed data from 82,225 emergent and elective PCI procedures performed at 47 centers participating in the Blue Cross Blue Shield of Michigan Cardiovascular Consortium (BMC2) between 2010 and 2012. In all 8,915 of the cases were transradial (10.8%) and 73,310 transfemoral (89.2%).

AKI, Bleeding Both Lower with Radial

AKI (primary endpoint; defined as an absolute increase in serum creatinine of at least 0.5 mg/dL) occurred at a rate of 1.40% in the radial group and 2.74% in the femoral group (P < 0.001).

Multivariate analysis, adjusting for baseline risk, time of treatment, estimated glomerular filtration rate (eGFR), and other factors, found that the radial approach appeared to reduce risk of AKI and postprocedural bleeding within 72 hours in the entire study population, with a trend toward lower risk of nephropathy requiring dialysis. There was no difference between groups for in-hospital mortality.

In a propensity-matched cohort of 8,857 pairs, the adjusted odds of AKI and bleeding remained lower with transradial PCI. Nephropathy requiring dialysis was similar for both access routes (table 1).

Table 1. Propensity-Matched Cohort: Radial vs Femoral Access

 
On logistic regression analysis, the lower risk of AKI with transradial access did not appear to be mediated by reduced risk of bleeding.

 Sensitivity analyses adjusting for hospital-level variability and bleeding events confirmed the relationship between AKI and access route, and also “demonstrated that the observed association . . . could potentially be explained by a moderately strong unknown confounder,” the authors note. They add, “AKI after PCI is a multicausal phenomenon induced by nephrotoxic effects of iodinated contrast media, changes in hemodynamics, and cholesterol embolization into the renal vasculature.”

Dr. Gurm and colleagues suggest several explanations for the apparent advantage of the radial approach in this context.

Transradial access “might minimize the risk of cholesterol embolization to the kidney,” they note. “Second, as has been demonstrated by other studies, contrast volumes used for PCI were lower for [radial vs femoral], although this difference was modest and probably not clinically relevant. Finally, it is possible that there was a reduction in episodes of hypotension because of hemodynamically significant bleeding or vasovagal responses in association with femoral sheath removal with resultant component of ischemic renal injury. Our study is unable to account for these differences.”

Results Hypothesis-Generating Only

Dr. Gurm told TCTMD in an email that the link between kidney damage and access route “is a novel finding and was a bit of a surprise. I would still like to consider our study as hypothesis generating and something that needs to be confirmed in a randomized trial.”

Of the various possible mechanisms, bleeding and its effect on acute renal stress seemed at the outset to be a likely culprit, he said, noting that the current analysis suggests this is not the case.

“I remain concerned that there may be other differences in the way radial patients are being treated that might explain some or all of this effect, although it is possible that there may be a true reduction in AKI with this approach,” Dr. Gurm cautioned. A major confounder may be the ‘healthy-patient effect’ as the radial approach is mostly used in healthier and younger patients, he added. Additional variables like frailty and proteinuria were not recorded in the registry and could potentially explain some of the observed differences, he said.

In the end, the reduction in bleeding and increase in patient comfort matter more when choosing radial access, Dr. Gurm emphasized. The reduction in AKI is the “icing on the cake,” he said. “It may well be an association.” 

In an email with TCTMD, Ian C. Gilchrist, MD, of Hershey Medical Center (Hershey, PA), proposed that the smaller catheters used in radial access and the technical skills possessed by radial operators may account for some of the benefit. “One of the weaknesses of this type of claims-based analysis is that the details of the procedures are difficult to determine,” he noted.

Any protective effect on the kidneys with radial should be considered a “bonus,” Dr. Gilchrist added. “As we still don’t fully understand renal failure after these procedures, cause and effect is not always clear,” he said. “Teasing apart the issue [by comparing the] 2 different access sites may in future analysis help to unravel or improve our understanding of this downside to cardiac catheterization.”

Many Unanswered Questions Remain

However, Somjot S. Brar, MD, MPH, of Kaiser Permanente (Los Angeles, CA), expressed skepticism. “I’m very suspect about whether there is a relationship,” he told TCTMD in a telephone interview. “There are still a lot of unanswered questions.”

The definition of AKI is “very broad,” no information was given about hydration, and the absolute difference in AKI rates is less than 1%, Dr. Brar pointed out. “Whether that is even meaningful is not entirely clear because so many patients in this study were at low risk of having kidney injury to begin with,” he said.

Furthermore, the fact that the reduction in AKI failed to be significant in the subgroup of patients whose eGFR would put them at highest risk of kidney damage is “concerning,” Dr. Brar commented, questioning the “biological plausibility” of the relationship between access site and AKI.

Study Details

Patients treated using transradial access were more likely to have hypertension, dyslipidemia, and diabetes but less likely to have previous MI and cerebrovascular or peripheral artery disease compared with those undergoing femoral access. They also were less likely to present with heart failure, cardiogenic shock, cardiac arrest, or STEMI. Mean contrast volumes were higher for femoral than for radial access (191.7 ml vs 189.4 ml; P < 0.001).

 

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Source:
Kooiman J, Seth M, Dixon S, et al. Risk of acute kidney injury after percutaneous coronary interventions using radial versus femoral vascular access: insight from the Blue Cross Blue Shield of Michigan Cardiovascular Consortium. Circ Cardiovasc Interv. 2014;Epub ahead of print.

 

 

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