Radial Access Ups Radiation Exposure for Patients, Physicians vs. Femoral Route

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Diagnostic cardiac catheterization performed via the radial route increases patient radiation exposure by almost one-fourth compared to femoral access, according to a large single-center study published in the March 2011 issue of JACC: Cardiovascular Interventions. The higher dose also exposes physicians to an additional 4 years’ worth of radiation over the course of their careers.

Researchers led by Mathew Mercuri, MSc, PhD, of Hamilton General Hospital (Hamilton, Canada), analyzed 5,954 diagnostic cardiac catheterizations performed at their institution between July 2006 and December 2008. They focused on differences in cumulative air kerma (AK), or the measure of radiation energy absorbed in a unit mass of air, between radial and femoral procedures. On the initial, unadjusted comparison, both fluoroscopy time and mean log AK readings were higher with radial access (table 1).

Table 1. Unadjusted Comparison

On multivariable regression analysis, radial access was independently associated with increased exposure (P < 0.0001) when compared with femoral access. On average, radial access would account for a 23% increase in measured AK for a typical patient (male, 65 years of age, BMI of 28.5 kg/m²). In terms of physician exposure, the researchers estimated that over a 20-year career, radial-access procedures would result in the equivalent of roughly 4 additional years’ worth of radiation exposure if the physician uses the radial route almost exclusively.

The exposure to the operator may be even higher due to the close proximity of the X-ray tube when performing a radial procedure, the authors note.

There were differences in mean log AK among operators (P = 0.0158), as well as a high level of variation in measured log AK among patients within each operator’s practice (P < 0.001), suggesting potential opportunities to reduce exposure, the researchers add.

There were 16 cardiologists who participated in the study, all of whom performed at least 250 diagnostic cases per year and have experience with both radial and femoral approaches.

The researchers conclude that “the study presented here may provide the best evidence to date regarding the relationship between radial access and increased radiation exposure to the patient during a diagnostic cardiac catheterization.” However, they cautioned against wholesale abandonment of radial access since “the measured AK was still far below the 2-Gy threshold for deterministic effects in the vast majority of patients in this study.”

In addition, they note, the increase in radiation exposure “would constitute a marginal increase in risk of stochastic effects, especially considering the age of most cardiology patients.”

Operators Should Take Precautions

“I think this is probably a real finding. The 23% is the key difference,” Steven Balter, PhD, of Columbia University Medical Center (New York, NY), told TCTMD in a telephone interview. “For the patient, it’s a minor factor, [but] for the staff, they need to be a little bit more prudent in protecting themselves.”

Dr. Balter noted that “99% of the operators have no idea how much radiation” they are exposed to.

“If you’re doing a radial, there is literature on how to protect yourself that is not used by enough operators,” Dr. Balter said. In particular, he recommended using arm shields to cut down on the increased radiation with radial procedures.

Timothy A. Sanborn, MD, of the University of Chicago School of Medicine (Chicago, IL), pointed to the increased fluoroscopy time as a key factor in the added radiation exposure with radial access. “I know from my experience and that of others, the radial can take more time because you have to manipulate catheters and different guides and sometimes it doesn’t seat very well,” he said in a telephone interview with TCTMD. “Even the radialists will admit to some technical issues. I think this study raises some concern.”

Learning Curve Debated

Dr. Sanborn, who described himself as a “99.9% femoral approach” practitioner, wondered if at least some of the cardiologists in the study had just adopted the radial approach and so were relatively early in the learning curve. “That information is not presented,” he said.

However, the study authors thought this unlikely. “If this were true,” they write, “the results observed in this study would suggest that each of the physicians observed is equally inexperienced with the radial technique. This seems improbable given the volume of cases per physician and the differing levels of training/experience within the group (eg, some physicians are not trained in interventional procedures, [and] when and where the physicians trained varies).”

Regardless, the study may not change the attitudes of those firmly in either the femoral or radial camp, Dr. Sanborn noted. “I would say an experienced radialist would say they can do it just as quick from the radial as the femoral. I don’t know if it’s going to change their practice,” he said. “For the femoralist, maybe he’s going to feel confident that he should stick with what he’s doing.”

But if the study is confirmed, then patients should be brought into the discussion, Dr. Sanborn stressed. “This does raise at least some concern that radials are a little more difficult, and patients should be informed of this,” he said. “If this is replicated in another study, [then when] a patient is offered radial vs. femoral, they should be told, ‘The radial might be a little simpler, you can get up and walk around quicker, but there may be a little bit more radiation.’”

 

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Source:
Mercuri M, Mehta S, Xie C, et al. Radial artery access as a predictor of increased radiation exposure during a diagnostic catheterization procedure. J Am Coll Cardiol Intv. 2011;4:347-352.

 

 

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