Commentary: The Learning Curve in Transradial Access: One Time When a Novice Interventionist May Shine

The innovation of endovascular techniques to manage vascular pathology has been nothing short of a revolution in patient care. Given the central location of the arterial system, the technique of open surgery is a major undertaking, whether it is a median sternotomy, craniotomy, or abdominal incision. In addition to the risks of the actual arterial surgery, open surgical access alone is associated with significant risks and prolonged patient recovery. Endovascular techniques minimize many of the access risks, leaving us primarily with the dangers of arterial manipulation.

However, even with a lower risk profile, significant hazards remain when using the femoral artery as an access site. Interventional cardiologists were the pioneers in transitioning to transradial access (TRA) to prevent significant bleeding and vascular injury, as well as all-cause mortality just from transfemoral access (TFA) complications. The interventional cardiology literature has shown in over 20 prospective randomized controlled trials that using the radial artery rather than the femoral artery dramatically lowers the access-site risk of endovascular therapy.^1–10 The MATRIX trial of over 8000 patients not only documented a 3-fold increase in complications from the femoral approach over the radial approach but a significant mortality benefit—just from avoiding the femoral artery. ⁹ This has precipitated a major shift away from the femoral artery as an access site in favor of the radial artery, with over 40% of cardiology procedures in the United States now performed transradially and over 80% in some regions of Europe and Asia. ¹¹

Neurointervention is a younger field than interventional cardiology and has consistently lagged behind interventional cardiology by 5 to 10 years, owing to the more challenging anatomy of the cerebral vasculature: smaller, more tortuous, and riskier to navigate than the coronary vessels. The conversion to radial access has been no exception, and prior to 12 to 18 months ago, very few centers were using the radial approach to perform neurointerventions.

However, there have been a number of recent publications documenting the experience of large cerebrovascular centers as they have converted to TRA, despite the lack of dedicated catheters designed for accessing the cerebral artery from the radial approach.^12–22 We congratulate Liu et al ²³ on their randomized controlled series comparing the transradial and transfemoral approaches in the October 2019 of the JEVT. The study is a significant addition to this body of work wherein they found TRA to be feasible, safe, and effective for cerebral angiography. Additionally, they showed that the TRA learning curve for novice interventionists is steeper but shorter (21–30 cases) as compared with TFA (41–50 cases). Furthermore, once the angiographic skill was acquired, the procedure times using TRA were significantly shorter (27.7 vs 40 minutes, p=0.03), contrast volume significantly less (95.9 vs 112.4 mL, p=0.03), and catheter exchanges significantly fewer (1 vs 3, p<0.001); the complication rate was also lower in the TRA group (2% vs 7%), although this was not significant (p=0.37). ²³

These findings again highlight the additional benefits of TRA over TFA. As I have committed to a primary radial practice, I have also focused on ensuring my fellows are proficient in TRA. Interestingly, I have observed that the fellows who have not had any prior angiographic experience appear to acquire TRA skills the fastest. In fact, our junior fellow last year was by far the most proficient at TRA that I have seen. My standard teaching mantra to TFA-trained physicians has always been “get to 50 consecutive cases” to overcome the learning curve. However, the study by Liu et al, ²³ as well as my personal experience, suggests that the number is likely lower for junior fellows, which highlights the importance of exposing neurointerventional trainees to TRA training early on to maximize TRA benefits and perpetuate innovation that improves patient care.