The RADIAL-TAVI trial rationale and design paper by von Ehr et al. in The American Journal of Cardiology was fascinating. The study answers an important clinical question: whether using the radial artery as secondary access during transfemoral transcatheter aortic valve implantation (TAVI) can reduce vascular and bleeding complications after a successful procedure. Valid scientific foundations and the randomized design are ideal for this task. We think there are a few protocol details worth looking at since they may affect how the trial’s results are understood and utilized.
The rationale draws heavily from the well-established superiority of radial over femoral access in percutaneous coronary intervention (PCI). , While this analogy is appealing, TAVI patients represent a fundamentally different population. They tend to be older, carry higher rates of peripheral arterial disease, and often present with calcified, tortuous vessels throughout. The radial artery, although far smaller and more peripheral, may behave differently in this group compared to younger PCI populations. Radial artery spasm, for instance, is reported in up to 10% of transradial PCI cases even in experienced hands. In TAVI, procedural efficiency and hemodynamic stability are crucial; even small radial access delays can have serious effects. The trial protocol lists inaccessible radial arteries as an exclusion criterion but does not specify how the 7 participating facilities will assess or standardize “inaccessibility.” This is important. Who is excluded from the center may cause a selection bias that randomization cannot correct.
The sample size computation needs scrutiny. The authors estimate 8% femoral complications and 2% radial complications, requiring 412 individuals. The 8% estimate from retrospective registry data is a good start. However, the greatest comparison, the PULSE registry subanalysis, found a femoral complication rate of 3.2%, not 8%. The study may be underpowered to detect the hypothesized difference if the femoral arm event rate is lower than assumed. Not just a statistical issue. It means the trial could find “no significant difference,” not because radial and femoral access are equal, but because the study was underpowered for real-world events. A prespecified interim analysis after 200 patients is planned, which is the appropriate time to reassess event rate assumptions and alter sample size. We strongly recommend this adaptable aspect in the statistical analysis plan.
Regarding operator experience, the protocol states that procedures will follow each center’s standard techniques, which is both practical and appropriate for a multicenter design. Yet we know from the PCI literature that the learning curve for transradial access is real and can influence complication rates in the early adoption phase. , The RADIAL-TAVI trial includes 7 centers, and it is not clear whether all of them have equal experience with radial secondary access in TAVI specifically. Some centers may be relatively new to the technique, while others are well-practiced. Without reporting operator or center-level experience as a covariate, it will be difficult to know whether observed complications in the radial arm reflect a genuine property of radial access or simply a learning curve effect. Stratifying the analysis based on center experience, even as an exploratory endpoint, would add meaningful depth to the interpretation.
We also want to highlight a gap in the secondary endpoints. Quality of life is captured via the EQ-5D-5L at 30 days, which is appropriate. However, the trial does not appear to include a dedicated assessment of upper limb function or hand discomfort- outcomes that matter specifically when the radial artery is used. Radial artery occlusion, though rarely symptomatic in young PCI patients, may be more clinically relevant in older TAVI patients who depend on their grip strength for daily activities. Incorporating a simple functional assessment of the accessed arm at follow-up would cost little and add important patient-centered data.
None of these observations detracts from a well-designed and timely experiment. The field requires the randomized data from the RADIAL-TAVI study to fill a gap in evidence. We present these considerations to urge prospective consideration before the recruitment window expires, since after data are obtained, it will be too late to capture what was not measured. We eagerly await the outcomes.
CRediT authorship contribution statement
Fatih Aydin: Conceptualization, Formal analysis, Investigation, Methodology.
Declaration of Competing Interest
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