Sometime in August of 1992, the first known angioplasty via radial access was performed. News of the novel procedure was met with little fanfare, and in the years that followed, few interventional practitioners pioneered the new technique for gaining percutaneous access. The nascent era of transradial access is now long in the past, and today, performing diagnostic and interventional procedures through the radial artery is not just commonplace, it is actually preferred practice in many parts of the world. In the United States, adoption of transradial techniques has been on an exponential climb for over a decade and is now poised to overtake transfemoral approach for use in percutaneous coronary intervention (PCI) within the next few years.
Moreover, transradial procedures are no longer just the domain of interventional cardiology, as specialists in interventional radiology and neurointerventional radiology have also adopted the technique in their own cases. As more and more published literature demonstrates benefits for transradial access in reducing complications and helping patients ambulate faster compared to transfemoral access, the idea of using the radial artery as the default option has steadily gained in popularity.
Interestingly, though, there is now a new concept in arterial access that proffers to challenge commonly held beliefs in interventional practice once again. Distal radial access was introduced almost simultaneously in the previous decade by Avtandil Babunashvili, MD, PhD, an interventional cardiologist based in Moscow, Russia; Alexandr Kaledin, MD, PhD, of St. Petersburg, Russia; and Farshad Roghani Dehkordi, MD, PhD, in Isfahan, Iran. Because it is viewed as a further refinement of transradial access at the wrist, and is therefore not an entirely new paradigm, distal radial access might not fit the technical definition of a disruptive innovation. At the same time, if the new technique eventually proves to be safer or provide greater benefit for patients’ and operators’ comfort, it still may displace proximal radial access as the default procedural option.
Recently, four interventional practitioners, representing different endovascular subspecialties, gathered to discuss their thoughts on the state of distal radial access techniques, the history behind it, and where they think it might fit into practice today and tomorrow. The following has been edited for length.
Radial access was first introduced almost 30 years ago. What was your motivation behind using radial access as opposed to other access sites?
Ferdinand Kiemeneij, MD, PhD: The major motivation to investigate and explore radial access in 1992 was the high rate of major bleeding complications after interventional procedures using the femoral artery. At the time, we had about 1 in 5 patients experiencing major complications — predominantly due to using every reasonable measure at our disposal to counteract the coagulation process after coronary stenting through large-bore guide catheters. Based on the pioneering work of Professor Lucien Campeau, Montreal, Canada, who in 1989 published a series of 100 patients who underwent percutaneous transradial angiography, I began to explore the possibility of performing transradial coronary angioplasty and stenting with my colleagues in interventional cardiology at the OLVG hospital in Amsterdam, because I believed it would be safer for patients. History has proven our original hypothesis correct, and yet we have also realized many additional benefits with radial versus femoral, such as cost benefits to the institution, better hemostasis, faster time to ambulation and discharge allowing outpatient treatment, lower nursing and staff requirements, benefits for room set up and ergonomics, and potential for higher patient volume, just to name a few.
Sandeep Nathan, MD, MSc: The U.S. adoption rate at this time, about 40% to 45%, is much lower than in many parts of Europe and Asia. A lot of that has to do with the fact that radial was not taught to many of us during fellowship training. But as we see more progressive operators adopt the techniques, it has been introduced into more training programs. For many U.S. operators, myself included, the potential to reduce complications was certainly the key motivator in converting. Additionally, the aspects of lower cost, faster discharge, and patient comfort are given different weight in the U.S. healthcare system compared to the rest of the world. The bottom line is really that many of us have realized that radial is preferable to femoral for a number of reasons. As I look back, converting to a radial-first approach and mindset is one of the few things that I have done post-fellowship that has completely transformed my practice.
Darren Klass, MD, PhD: I started with radial access in April 2014, and it quickly became my default. There is not the same incidence of bleeding complications in interventional radiology procedures as in interventional cardiology, so the movement to radial has really been motivated by patient preference in the majority. Interventional radiology procedures do not require the same degree of anticoagulation as coronary intervention, hence the lower bleeding rates, but this risk is not negligible by any means. While patient comfort is a driver, so too is the need to make procedures safer. What is interesting to me is that while it was our patients that really got interventional radiology interested in radial access, there are definite benefits for the operator, in terms of the room set up, and for the procedures we perform, as it easier to access vessels in the pelvis and abdomen coming from the radial artery.
Ajit S. Puri, MD, DM: The neurointerventional radiology field has only very recently begun to adopt radial access. For myself and many of my colleagues, the outcomes data being compiled by the interventional cardiology field became almost impossible to ignore. Radial access is demonstrably safer for our patients than femoral access, while offering a more elegant approach to the delicate procedures we perform. Add to that the fact that patients are asking for radial access and it has become hard to justify using femoral as the primary site.
What motivated you to think about using distal radial access?
Dr. Puri: I actually started with distal radial access and only use proximal radial artery access for cases not done via distal radial access. Right now, 100% of my diagnostic and more than 95% of my intervention practice is performed using distal radial access. My sense is that distal is even safer than proximal radial access in terms of achieving hemostasis, and it is also very amenable for ultrasound-guided access.
Dr. Kiemeneij: This is very interesting to me for a couple of reasons. When radial was introduced, it took a long time to get people to convert. Almost all operators felt comfortable with femoral, and there was maybe some reluctance to abandon a technique that was very familiar. Distal radial access is a new technique, but comparatively, we are seeing a much more rapid adoption of distal compared to the changeover from femoral to radial. I would like to think that adopting radial encouraged a mindset to make incremental improvement to our procedures, and that is what is feeding a lot of the interest in distal. But this also raises an interesting paradigm. I think it may actually be easier for those in training to learn distal first and then learn proximal radial. If you are coming from a situation of having no experience with radial access, learning distal first may put you at an advantage.
For me personally, I am interested in distal radial access because it makes sense from an anatomic perspective. The distal aspect of the radial artery presents more superficially and runs over hard bone, which makes it easier to compress, suggesting the potential for faster and easier hemostasis. As well, puncturing distal to the superficial palmar branch theoretically maintains antegrade flow through the radial artery even if distal occlusion occurs, thereby likely preventing thrombosis over a long segment. Proximal radial artery occlusion is the Achilles’ heel of transradial, making more frequent future use of this vessel impossible, exposing the patient again to higher risk femoral puncture. In case the distal radial artery occludes, the patency of the proximal radial artery serves as a backup entry site. In addition, distal allows a more comfortable hand position for the patient during the procedure, increasing patient comfort and also operator comfort, especially for access via the left radial artery.
Where could distal access fit into practice? Is there enough evidence to suggest it should be the default option?
Dr. Nathan: I work in a busy training center, so from that perspective, teaching “distal first” works somewhat against the interest of having our fellows learn all of the techniques. When fellows leave our program, they need to be able to adapt to the needs of each particular patient. Our obligation is to be certain our trainees are proficient in all access site techniques, so we really cannot teach one particular technique to the exclusion of another. Related to that is the fact that many patients will need repeated access over time. The patient with a heart transplant is a good example. As he or she requires annual angiograms, there is a need to rotate the puncture site. In such a patient, it might be preferable to save the distal radial access site as a non-femoral option to use later on.
Dr. Kiemeneij: The science has established that radial should be preferred over femoral due to lower complication rates, but the issue of which radial site to use first is one of the important questions left to be answered. It has been suggested that distal radial access is associated with lower rates of radial artery occlusions. But it may also be the case that using distal access protects the radial artery at the wrist, but leaves the distal site at the puncture site vulnerable to closure. Does that mean we use distal as the default access site because we believe, and because the anatomy suggests, it will lead to even lower complication rates? Answering that question would require randomized clinical trials, but the complication rates are so low, it would mean enrolling very large numbers of patients and years of follow-up. Even if such a study were feasible, what do we do in the interim? And what do we do with negative data? Is that a reason to abandon distal or to improve the technique? Also, I think it is of equal importance to prove that distal access does not impair hand function.
Dr. Klass: There are some other unanswered questions with distal access, such as the loss of distance during some procedures. This is most relevant in peripheral intervention in the pelvis, distal vessels in the abdomen, and intervention below the inguinal ligament.
Dr. Puri: There is about a few centimeters you lose, but there are ways we can accommodate for the taller patient and patients with tortuous vascular anatomy. What I have done in my practice is to combine using the longer length guide catheter and use the check-flow Tuohy borst instead of the regular RHVs. This saves few centimeters to use for the intermediate microcatheter lengths.
Dr. Kiemeneij: I think this highlights something else that is different with how distal access techniques are developing: when we started radial, we had to work with tools used in femoral, and they were not always ideal to use, but now, device manufacturers are designing needles, wires, sheaths, catheters, and hemostasis devices specifically for distal access. There is also a very active community of operators from around the world discussing the pros and cons of distal on social media. That kind of information sharing has really helped spread the message on distal, and it has been paralleled by a growing body of published literature. All four of us are also involved as instructors for distal courses sponsored by Merit Medical; the support from industry, giving us a venue to not only lecture but to share information, cases, and techniques in an open format, has been very helpful. That is all to say there are a lot of things that will help increase our understanding of distal access techniques and where they fit in to practice. There are indeed many unanswered questions, but we have a lot more access to information this time around than in the pre-transradial era.
Dr. Nathan: This may fall into the category of playing devil’s advocate, but there is currently a lack of robust, randomized clinical trial data showing the clear benefits of defaulting to distal. Some of the issues with trial recruitment were acknowledged earlier, and they are relevant. But, while there is data to support radial over femoral, and there is data to support the continued development of distal radial as a non-femoral option, I am not sure there is truly convincing argument one way or the other on whether distal radial should be the default. The good news is that several groups have heeded this call and clinical trials in this space are now underway — we should have some answers within the next two years or so.
Dr. Kiemeneij: The very low complication rate with distal radial access, and actually with proximal radial access, is a confounding variable in this regard. You are correct in that it would likely take 10 years or more and tens of thousands of patients to accrue the necessary data to show any difference in complication rates between proximal and distal access. I know that there are clinical randomized trials underway in Russia, Europe, the U.S., and Asia. But in the end, it may not be ethical to wait the 10 or 15 years it might take to get a solid collection of data we need to answer these questions. What may be necessary for the continued development of distal radial access — and as you highlighted, there is scientific rationale to support continued development — is for each of us to look at outcomes in our own practices. Talk with staff, talk with patients, and look at our own outcomes. I am convinced that those sorts of experiences will continue to build enthusiasm for distal techniques. There may be some lessons we can learn from the transition to femoral to radial. At first, radial operators were the outliers, but as they discussed the technique with colleagues, a community started to form and grow, and in the end, femoral became the outlier. We will see if a similar trend will emerge with distal radial.
Dr. Klass: Another way to look at this may be to ask whether it always has to be patient safety that drives a new way of doing things? What happens if you look at things other than patient complications? At this point, it is fair to say that distal radial access is non-inferior to proximal radial access — there is no data to support it being in any way harmful. If that is the case, then we can look at patient preference, hemostasis efficacy and time, and potentially getting patients up and about quicker as differentiators. I am not 100% convinced that we will ever get to a point where we got to with femoral versus radial and the marked benefits of the latter, but I think maybe what distal radial might do is lead us to look at overall outcomes a little bit differently and say, “Yes, this is as safe as conventional radial is, but it is more comfortable for the patient, especially going from the left, hemostasis is faster, and occlusion rates are lower.”
Are there any unexpected benefits associated with distal radial access?
Dr. Klass: Something that gets overlooked, perhaps, is the advantages for room set up. In interventional radiology a lot of our procedures are performed from the left wrist. Arranging the room for left radial, especially if that room is used by multiple operators, can be difficult. At our institution, we have one room where there is no radiation protection on the left side of the bed, so we cannot work from the left, and therefore have to flip the patient 180 degrees. This is not possible in many rooms and remains a source of frustration with operators and, I feel, may hamper adoption. When using distal radial access, though, you simply set the room as though it were a femoral case and then position the left hand at the right groin — you are moving the access site to the operator rather than positioning the patient so that the operator can gain access. For operators for whom room set up is a hurdle for them to get started with proximal radial, distal radial seems to answer this problem.
Dr. Nathan: I mentioned the lack of data just before, but one of the interesting things that has occurred in the radial era is that we have seen different specialties adopt this technique and begin to discuss case parameters that intersect. Catheter-based vascular therapies have been historically very siloed, and I think there’s an interesting opportunity for different types of practitioners to pool their data, with the thinking that “It doesn’t matter what you do with the catheter once you’re in there, we’re just interested in the access and the closure and the challenges encountered with passing a catheter from a snuffbox approach.”
Dr. Klass: I think the four of us discussing this right now is a great example of that. We have neurointerventionists, cardiologists, and interventional radiologists sitting together discussing the exact same thing. When, ever, in medicine has that happened? I recently accessed the last 20 or 30 studies on distal radial and all three specialties were represented. And that’s what I think is so great about this, is that you have the three endovascular specialties all learning and discovering at the same time. And if this does nothing else, it has created this cross-pollination between the three specialties. I tell all the interventional radiologists that I train that the first thing you should do when you get back to your hospital is go and speak to your cardiology colleagues, because they have all the experience with this.
It has been suggested that distal techniques may be associated with a learning curve. Is this true, and are there strategies operators can employ to navigate early cases?
Dr. Kiemeneij: The transition from proximal to distal radial access is quite different than what we experienced in moving away from femoral. The move from femoral to radial represented a true paradigm shift, whereas distal access is more so a refinement of technique. That means there is a shorter learning curve learning distal if you are already familiar with proximal compared to moving from the groin to the wrist.
Dr. Puri: The biggest thing is you need buy-in from your entire team, from the technologists to the nurses to the staff, all the way from the short stay to the PICU to the ER. Because it is not only the people who are in the angio suite, but those before the angio suite and after the angio suite who are taking care of these patients, they need to have the buy-in. So, you need to have them educated.
Dr. Klass: Do you believe in selecting cases for learning the procedure?
Dr. Puri: No, jump right in. Every case is a good case.
Dr. Nathan: I think that is a great point, because I think if you don’t push yourself out of your comfort zone, you always stay in your comfort zone, and then radial becomes relegated to morbidly obese or anticoagulated patients or those with a hostile periphery. The issue of case selection bias aside, that is a setup for failure. Whereas, every case is a learning case. You learn something in terms of catheter manipulation, troubleshooting, spasm, perhaps even complication avoidance, and I think selecting cases, as opposed to trying to do this the majority of the time, is a frequently made mistake.
Dr. Klass: In my experience, there are two types of practitioners who run into problems with new access techniques. There’s the practitioner who was never trained, who thought, “Oh, it’s just like any other artery, I can stick it, I’m good.” That is a common mistake, where people don’t get trained properly, so they don’t have proper hemostasis techniques. I would say to that person, if you do not choose to attend one of the many courses at major meetings or industry sponsored programs like ThinkRadial, at least work with an experienced operator who is willing to proctor your early cases. The second is the dabbler, which may be a more common problem and is more detrimental to the learning process. This is the operator who does a few cases, sees longer fluoroscopy times, and then stops because that is more than what they are accustomed to. In these cases they would rather stop their radial practice instead of working through learning curve and then seeing the fluoroscopy times decrease, even more so than their times for the same case done transfemorally.
1Department of Cardiology, MC Zuiderzee Hospital, Lelystad, the Netherlands
2Vancouver General and UBC Hospitals, Vancouver, Canada
3Division of Neuroimaging and Intervention, Department of Radiology, University of Massachusetts, Worcester, Massachusetts
4University of Chicago Medical Center, Chicago, Illinois