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The odds of successful transradial percutaneous coronary intervention (PCI) are highest when operators have performed at least 50 such procedures, according to a study published online August 2, 2011, ahead of print in Circulation: Cardiovascular Interventions.

Investigators led by Asim N. Cheema, MD, PhD, of Hamilton General Hospital (Hamilton, Canada), analyzed data from 1,672 patients who underwent nonurgent single-vessel PCI using transradial access at St. Michael’s Hospital in Toronto, Canada, from 1999 to 2008.

The procedures were performed by 28 operators, including interventional fellows and staff physicians with experience in transfemoral PCI but no prior transradial experience or training. The cases were stratified into groups of 50 based on operator career transradial PCI volume:

• 1 to 50 cases (655 patients): 22 operators
• 51 to 100 cases (344 patients): 14 operators
• 101 to 150 cases (213 patients): 7 operators
• 151 to 300 cases (141 patients): 5 operators

In addition, 319 cases performed by 12 operators with more than 300 career transradial procedures served as controls.

Baseline and angiographic characteristics of the study population were similar across the case volume groups.

Inexperience Apparent in Early Cases

Overall, transradial PCI failed in 4% of cases. The failure rate was higher in the lowest-volume group (1-50 cases) compared with the next highest group (51-100; P = 0.007) and the control group (P = 0.01). There was no difference among groups in the number of guide catheters used. However, contrast use was greater in the lowest-volume group compared with the 151-300-volume group (P = 0.02) and the control group (P = 0.05). And fluoroscopy time was higher in the lowest-volume group than in the 100-151-volume group (P = 0.04) and the control group (P = 0.02). Rates of all procedural metrics declined with increasing experience (table 1).

Table 1. Procedural Outcomes by Operator Experience

Transradial PCI failed due to a number of reasons including radial artery spasm (38% of patients), subclavian tortuosity (16%), poor guide catheter support (16%), inability to obtain arterial access (10%), and radial artery loop (7%). On logistic regression analysis, case volume was correlated with transradial PCI failure (P = 0.0028). The odds of failure decreased by 32% over each 50-case interval per operator, with the most dramatic decline coming with the first 50 cases. No interaction was seen between case volume and operator status (ie, trainee vs. staff member).

In the subgroup of operators who contributed to all 4 case volume groups, a similar pattern of declining failure rates with increasing experience was observed, with failure rates significantly higher for the 1-50 case group vs. the 51-100 case group.

Dr. Cheema and colleagues say that although the learning curve is steep, it appears to plateau somewhere around 50 cases. Moreover, identification of a minimum volume for optimal clinical outcome can serve as a guide for transfemoral operators seeking to incorporate a higher proportion of transradial procedures into their practice and for training courses and certification organizations trying to define minimum standards for proficiency.

The authors acknowledge that the study’s exclusion criteria significantly limited the types of cases treated via radial access. “A different learning curve may exist for complex coronary interventions, including multivessel, vein graft, primary, and ad hoc PCI, and for patients with comorbidities such as obesity and old age,” they say.

Data Solidify 50-Case Cutoff for Basic Competence

“This is one of the better looks at the actual learning curve for radial PCI,” said Ian C. Gilchrist, MD, of Hershey Medical Center (Hershey, PA), in a telephone interview with TCTMD. “Prior publications [have focused on] single experiences, and there is a lot of variation from doctor to doctor. Having 20-odd operators here helps smooth some of that out.”

In terms of the volume of radial procedures needed to achieve basic competence, “the number 50 has been bandied about for a while, and this paper helps solidify that with some science,” he said. But it is important to keep in mind that these were interventional procedures, Dr. Gilchrist observed. Diagnostic catheterizations do not count toward that total because they are simpler. Nonetheless, in the study the learning curve may have been eased since the operators in the low-volume group may have already gained considerable experience with radial access performing diagnostic catheterizations.

Dr. Gilchrist also pointed out that these procedures took place in the context of “a lot of collegial support.” In other words, learners had many experienced radialists in the institution to call on for guidance. “That is a very different situation from a doctor showing up in the cath lab and announcing that he is going to be the first one to learn the radial technique,” he noted.

On the other hand, if the operators had used shorter, hydrophilic sheaths and 5 Fr rather than 6 Fr catheters—practices that are more common today—the learning curve might have been lessened somewhat, Dr. Gilchrist commented.

Learning Curve Does Not Harm Patients

Overall, the findings underscore the fact that the learning curve was generally quite safe for patients, Dr. Gilchrist said. Though the early radial failure rate was fairly high, ‘failure’ simply meant that the operator had to switch from the radial to the femoral artery to complete PCI, he pointed out. And importantly, for experienced femoral operators learning the radial approach, once the catheter reaches the central aorta, the remainder of the procedure is very similar.

Furthermore, the differences in contrast volume and fluoroscopy time, though statistically significant, were minor and varied widely among operators, resulting in some overlap between the different volume groups, Dr. Gilchrist noted.

The 50-case cutoff likely is due to the fact that by that point, new radialists have encountered the routine variations and improvement starts to level off, Dr. Gilchrist said. But as they take on more and more challenging cases, and begin to use more complex technology like rotablators, they still need to exercise some forethought regarding how to proceed using the radial approach, he cautioned.

The bottom line is that the learning curve is quite reasonable, especially for experienced interventionalists, Dr. Gilchrist observed. “You have to recognize it, but you shouldn’t fear it,” he said, adding that the key is to commit to the technique rather than using it mainly as a fallback when the femoral approach becomes problematic.

Study Details

The indications for PCI were stable angina (55% of patients), unstable angina (7%), non-STEMI (30%), and STEMI (1%).

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