Transradial Access Gains Converts Among US Interventional Neurologists

Mitchel L. Zoler

March 06, 2020

LOS ANGELES — The safety advantage that has already coaxed U.S. interventional cardiologists to switch many of their routine catheterizations from femoral-artery entry in the groin to a radial-artery approach through a patient's wrist is now prompting a similar shift among U.S. interventional neurologists, who are increasingly pivoting to transradial access when performing many neurovascular procedures.

"It's growing dramatically in U.S. practice. It may be hype, but there is big excitement. We are still in an assessment mode, but the adoption rate has been high," Raul G. Nogueira, MD, said in an interview during the International Stroke Conference sponsored by the American Heart Association.

"The big advantage [of transradial catheterization entry] is elimination of groin complications, some of which can be pretty bad. Is it safe for the brain? It's probably okay, but that needs more study," said Dr. Nogueira, professor of neurology at Emory University and director of the Neurovascular Service at the Grady Marcus Stroke and Neuroscience Center in Atlanta.

His uncertainty stems from the more difficult route taken to advance a catheter from the wrist into brain vessels, a maneuver that requires significant manipulation of the catheter tip, unlike the path from the right radial artery into the heart's arteries, a "straight shot," he explained.

To reach the brain's vasculature, the tip must execute a spin "that may scrape small emboli from the arch or arteries, so we need to look at this a little more carefully," ideally in a prospective, randomized study, he said. "We need to see whether the burden of [magnetic resonance] lesions is any higher when you go through the radial [artery]."

Some of the first-reported, large-scale U.S. experiences using a radial-artery approach for various neurovascular procedures, including a few thrombectomy cases, came in a series of 1,272 patients treated at any of four U.S. centers during July 2018 to June 2019, a period when the neurovascular staffs at all four centers transitioned from primarily using femoral-artery access to using radial access as their default mode.

During the 12-month transition period, overall use of radial access at all four centers rose from roughly a quarter of all neurovascular interventions during July to September 2018 to closer to 80% by April to June 2019, Eyad Almallouhi, MD, reported at the conference.

During the entire 12 months, the operators ran up a 94% rate of successfully completed procedures using radial access, a rate that rose from about 88% during the first quarter to roughly 95% success during the fourth quarter tracked, said Dr. Almallouhi, a neurologist at the Medical University of South Carolina in Charleston.

The rate of crossover from what began as a transradial procedure but switched to transfemoral was just under 6% overall, with a nearly 14% crossover rate during the first quarter that then dropped to around 5% for the rest of the transition year. Crossovers for interventional procedures throughout the study year occurred at a 12% rate, while crossovers for diagnostic procedures occurred at a 5% clip throughout the entire year.

None of the transradial patients had a major access-site complication, and minor complications occurred in less than 2% of the patients, including 11 with a forearm hematoma, 6 with forearm pain, and 5 with oozing at their access site. The absence of any major access-site complications among the transradial-access patients in this series contrasts with a recent report of a 1.7% rate of major complications secondary to femoral-artery access for mechanical thrombectomy in a combined analysis of data from seven published studies that included 660 thrombectomy procedures (Am J Neuroradiol. 2019 Feb. doi: 10.3174/ajnr.A6423).

The other three centers that participated in the study Dr. Almallouhi presented were the University of Miami, Thomas Jefferson University in Philadelphia, and the University of Pittsburgh.

Of the 1,272 total procedures studied, 83% were diagnostic procedures, which had an overall 95% success rate, and 17% were interventional procedures, which had a success rate of 89%. The interventional transradial procedures included 62 primary coilings of aneurysms, 44 stent-assisted aneurysm coilings, 40 patients who underwent a flow diversion, 21 balloon-assisted aneurysm coilings, and 24 patients who underwent stroke thrombectomy.

The size of the devices commonly used for thrombectomy are often too large to allow for radial-artery access, noted Dr. Nogueira. For urgent interventions like thrombectomy "we use balloon-guided catheters that are large-bore and don't fit well in the radial," he said, although thrombectomy via the radial artery without a balloon-guided catheter is possible for clots located in the basilar artery. Last year, researchers in Germany reported using a balloon-guided catheter to perform mechanical thrombectomy via the radial artery (Interv Neuroradiol. 2019 Oct 1;25[5]:508-10).

But it's a different story for elective, diagnostic procedures. "I have moved most of these to transradial," Dr. Nogueira said. He and his coauthors summarized the case for transradial access for cerebral angiography in a recent review; in addition to enhanced safety they cited other advantages including improved patient satisfaction and reduced cost because of a shorter length of stay (Interv Cardiol Clin. 2020 Jan;9[1]:75-86).

Despite his enthusiasm and the enthusiasm of other neurointerventionalists for the transradial approach, other stroke neurologists have been more cautious and slower to shift away from the femoral approach.

"Our experience has been that for most cases it's a bit more challenging to access the cervical vessels from the radial artery than from the traditional femoral approach. For arches with complex anatomy, however, the transradial approach can be of benefit in some cases, depending on the angles that need to be traversed," commented Jeremy Payne, MD, director of the Banner Center for Neurovascular Medicine and medical director of the Banner–University Medical Center Phoenix Comprehensive Stroke Program. Dr. Payne highlighted that, while he is not an interventionalist himself, he and his interventional staff have regularly discussed the transradial option.

"In the cardiology literature the radial approach has been very successful, with better overall safety than the traditional femoral approach. Largely this seems to do with the anatomy of the aortic arch. It's simply a more direct approach to the coronaries via the right radial artery; getting the wire into the correct vessel is significantly more difficult the more acute the angle it has to traverse," such as when the target is an intracerebral vessel, Dr. Payne said in an interview.

"Our experience in the past 6 months has been about 25% transradial for some of our procedures, mainly diagnostic angiograms. We don't find any difference in safety, however, as our transfemoral procedures are already very safe. One of the benefits of a transradial approach has been that a closure device may not be needed, with fewer vascular complications at the access site, such as fistula formation. We use ultrasound for access, and have not seen a difference in those approaches at all so far. One might argue that using ultrasound to establish access would slow us down, but so far our fastest case start-to-recanalization time in an acute stroke this year was 6 minutes, so speed does not appear to be a limiting issue.

"Another concern overall for transradial access is the potential limitation in the tools we may be able to deploy, given the smaller size of the vessel. It is reassuring [in the report from Dr. Almallouhi] that a variety of cases were successfully completed via this approach. However, fewer than 2% of their cases [24 patients] were apparently emergent, acute strokes, lending no specific support to that context. I do not expect that to change based on this paper," Dr. Payne concluded.

"It is not clear to me that transradial neurointervention will change much. We have excellent safety data for the femoral approach, a proven track record of efficacy, and for most patients it seems to afford a somewhat wider range of tools that can be deployed, with simpler anatomy for accessing the cervical vessels in most arches. It is reassuring that the results reported by Dr. Almallouhi did not suggest negative outcomes, and as such I suspect the transradial approach at least gives us an additional option in a minority of patients. We have seen in the past 5-10 years an explosion of tools for the endovascular treatment of stroke; transradial access represents another potential strategy that appears so far to be safe," Dr. Payne said.

Drs. Nogueira, Almallouhi, and Payne had no relevant disclosures.

International Stroke Conference (ISC) 2020: Abstract 64. Presented February 19, 2020.

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