Could radiation exposure be the Achilles' heel of distal transradial artery access?

Distal transradial access for vascular interventions has gained ground recently. While the novel approach is associated with reduced radial artery occlusion and faster hemostasis, it could be related with prolonged procedural time, higher crossover rate and increased radiation, comparing to conventional transradial approach. Whether the radiation is increased in the procedures performed by the novel approach remains unambiguous. In the specific article, we aim to review the current literature and to propose possible explanations for this phenomenon. Could radiation be the Achilles' heel of distal transradial artery access?

In 2017, Kiemenej et al proposed a novel approach for vascular access through anatomical snuffbox. Distal transradial access (dTRA) has gained ground for both cerebral and coronary angiography and interventions., Notably, dTRA could be used for complex cases, such as the recanalization of chronic total occlusions, as a second access site for transcatheter aortic valve implantation, for coil embolization and carotid stenting.3, 4, 5 The first observational, non-randomized studies supported that dTRA could be used as an alternative approach for conventional transradial access (TRA), presenting it is as a safe and feasible method. Recently, the first large-scale randomized control trials comparing dTRA versus TRA for coronary angiography and interventions were published, confirming that radial artery occlusion and hemostasis time were decreased in dTRA arm; nevertheless, crossover rate, procedural time and radiation were increased.6, 7, 8

The radiation consists a major disadvantage of coronary angiography and interventions, as it has been associated with numerous serious diseases for the interventional cardiologists; glaucoma, brain tumors and skin cancer. Fluoroscopy time consists the total amount of time fluoroscopy used and it has been utilized as the simplest indicator for radiation. While FDA considers fluoroscopy time as a surrogate marker for periprocedural radiation exposure, recent study supports that Dose Area Product (DAP) and Air Kerma are more precise indicators. DAP and Air Kerma are two measurements commonly used to represent the dose patient receives, during such procedures. Generally, DAP provides more a general dose reference and acts as risk scale, while Air Kerma predicts more accurately the radiation dose received by the patient in a particular spot. DAP reflects the sum of fluoroscopy time, and the number of cine exposures during the procedure. Although fluoroscopy time contributes to DAP estimation, they are not affected equally (See Fig. 1).

Fig. 1

Parameters for estimating Radiation Dose during Interventional Procedures.

Recently, Tsigkas and his colleagues concluded that a higher DAP was found in dTRA group, comparing to TRA. The increase was small but statistically significant; absolute difference was 3.82 Gy/cm2 in DAP and 0.764 mSv in patients’ effective dose. Paradoxically, this trial did not detect any difference in fluoroscopy time between the two arms., The most recent DISCO RADIAL, the largest randomized trial in this topic, did not find any difference regarding radiation dose between the two arms., A numerically but not significantly increase in DAP in dTRA group was also noticed in another randomized trial. Fluoroscopy time was significantly increased in the dTRA comparing to TRA arm in a non-randomized study by Lu et al. A recent meta-analysis, including four randomized-control trials, supported that fluoroscopy time was elevated in dTRA group in a non-significant way, while another claimed that fluoroscopy time was significantly longer in dTRA arm., However, no difference was observed in DAP.

Moreover, studies investigating the role of dTRA in neurointerventions concluded in similar results. More specifically, Hoffman et al compared retrospectively dTRA versus TRA for performing cerebral angiography. A total of 244 patients were included and TRA was associated significantly with shorter fluoroscopy time and lower radiation dose.

It is clear that the existing literature cannot unambiguously answer to whether dTRA approach in vascular interventions increase the DAP and fluoroscopy time. It could be hypothesized that the lack of catheter support engagement during maneuvers or the extra distance from the puncture site to the target vessel with dTRA could attribute to this conclusion. These findings require validation from additional clinical trials; the results by the DOSE trial (NCT04023838) may shed the lights on this dilemma, as its primary endpoint is the radiation dose of operator.

In our opinion, dTRA approach could be related with higher fluoroscopy time and radiation exposure, due to the distal catheterization and the more catheters’ manipulation. The radiation exposure according to the learning curve of each operator has not been studied yet; nevertheless, we do not believe that the impact of learning curve could affect these parameters.

In conclusion, exposure to radiation after dTRA approach could be a major drawback of this novel technique. Current literature shows a notable trend, but more research is required to conclude whether these limited and preliminary data reflect the reality behind “snuffbox” approach.

Funding sources

None.

Declaration of competing interest

None.