Access Site Used for Cardiac Cath Does Not Influence Radiation Exposure for Patients
Among operators with high proficiency in radial procedures, radiation exposure to patients during angiography is similar regardless of access site, according to a study published online July 22, 2015, ahead of print in JACC: Cardiovascular Interventions. However, operators are exposed to slightly higher levels of radiation while performing left- as opposed to right-radial procedures.
“Increasing operator experience continues to improve radiation use for all access sites, including [the femoral artery],” say Samir B. Pancholy, MD, of Commonwealth Health (Scranton, PA), and colleagues. “Operator radiation exposure is likely a function of the operator’s distance from the radiation source and shielding; hence, in a catheterization laboratory setup favoring right-sided procedures, it is higher with [left-radial procedures].”
For the REVERE trial, Dr. Pancholy and colleagues randomized 1,493 patients undergoing diagnostic cardiac catheterization at a single tertiary care center in India between August 2012 and November 2013 to femoral, left-radial, or right-radial access. All procedures were performed by 5 operators who were classified by level of career experience in radial procedures (both diagnostic and interventional) as:
- Low: 100 to 500 cases
- Medium: 501 to 999 cases
- High: More than 1,000 cases
Demographic variables were similar among the 3 patient groups. There were 20 instances of access-site crossover (6 from right to left radial, 8 from left to right radial, 3 from right radial to femoral, and 3 from left radial to femoral). Additionally, more catheters were used in the left-radial and femoral groups than in the right-radial group (P = .0001), and the median number of cineangiograms acquired was lower in the femoral vs left-radial group (P = .005) as well as in the left-radial vs right-radial group (P = .0001).
Cumulative air kerma (primary endpoint) was similar across access sites. Similarly, there were no differences in dose-area product or fluoroscopy time. Operator exposure did not differ between femoral and right-radial procedures, but it was higher for left radial compared with the other 2 access types (table 1).
Overall, operators with low experience had greater radiation exposures—including higher air kerma and dose-area product—and longer fluoroscopy times than those in with medium or high experience. Increasing operator experience was associated with decreasing median air kerma, with continuing reduction in dose seen across the low to medium to high groups (569 vs 418 vs 324 mGy; P = .0001). This pattern also held true for air kerma per cineangiographic run. Furthermore, when the femoral group was analyzed separately, the inverse relationship between air kerma and operator experience persisted.
According to the study authors, the trial “emphasizes that several other factors, including patient age, sex, weight, and procedural variables, such as number of cineangiographic acquisitions, number of catheters needed to complete the procedure, and, importantly, operator experience are the predominant drivers of radiation exposure.” These findings are in line, they add, with the radiation substudy of the RIVAL trial.
Notably, Dr. Pancholy and colleagues say, the findings “suggest that previously published data from observational studies showing higher radiation exposure with [radial procedures] are likely confounded” by these factors.
“I think that’s a fair comment,” Stephen Balter, PhD, of Columbia University Medical Center (New York, NY), told TCTMD in a telephone interview. “An important message that we see from this study is that experience counts, so possibly in some of the previous literature, one of the issues may have been that operators were relatively inexperienced in doing radial. What’s important is that [it seems patients] are not paying a radiation toll because their exposures are the same regardless of the access site. That is reassuring.”
As for the left- vs right-radial differences seen in operator exposure, Dr. Balter said the study “gives some clues as to what may be happening” but added that more work is needed to better understand whether the issue is related to the positioning of the operator (ie, working from the left side of the table or bending over the patient) and/or the positioning of radiation shields.
“It’s not clear from this study whether operators who were working on the left side of the patient also had the shielding on the left side of the patient,” Dr. Balter noted. “The discussion hints at the possibility that in some cases the shields may not have been moved, and the lesson there is to always be aware and move your shields to the left.”
Dr. Balter also observed that the study involved diagnostic procedures and therefore the results may vary with interventional procedures that last longer and are more involved.
Ian C. Gilchrist, MD, of Penn State Hershey Medical Center (Hershey, PA), took a slightly different point of view regarding experience and exposure.
“One thing that you wonder about with this paper is what kind of understanding each of these operators has of their personal radiation exposure,” he said in a telephone interview with TCTMD. “A guy who is on the high end of the experience spectrum may be more concerned than someone doing fewer cases and that may cause him to take his radiation exposure more seriously than the other guy. To me, this is not necessarily showing an association with the learning experience of doing radials but maybe more of the idea that I need to pay attention to how much I’m being exposed to.”
Dr. Gilchrist agreed with the assertion that prior studies may have involved operators not as facile with all approaches.
“But this paper has the same problem that many of the other papers have had, which is a very small number of operators being looked at,” he said. As such, “there is a lot of room for individual variation that has nothing at all to do with access site. The bottom line is you really need a larger study to look at this issue.
“Although the differences in this study are fairly small, the confidence intervals are large and that to me speaks to the variability between operators and their procedures,” he continued. “It’s not the difference in radiation between the different access sites that should be alarming, but the fact that there is so much difference in amount of radiation being used by different operators; we should be focusing on how to tighten that. The bigger picture is that there is still lots of room for improvement.”
Pancholy SB, Joshi P, Shah S, et al. Randomized evaluation of vascular entry site and radiation exposure: the REVERE trial. J Am Coll Cardiol Intv. 2015;Epub ahead of print.
- Dr. Pancholy reports serving as a consultant for Terumo.
- Drs. Balter and Gilchrist report no relevant conflicts of interest.