Coronary Catheter Course Via the Left Radial Approach Is Diametrically Opposed to the Course Via the Femoral Approach: A Stroke Paradox

Novel Teaching Points.

• •The course taken by catheters along the arch of the aorta when it is accessed through the LRA may be diametrically opposed to that taken via the femoral approach.
• •Atherosclerotic plaque is differentially distributed along the arch of the aorta.
• •The relationship of the catheter course along the differentially distributed plaque in the arch of the aorta may explain the surprisingly comparable stroke rates that accompany procedures conducted via the TFA and the LRA.

The a priori assumption that the left radial approach (LRA) and the femoral approach are quite similar may be untenable. The course followed by catheters that are advanced from the left arm to the heart, vs to the femoral artery, may be different in the arch of the aorta. Given that the bulk of the atheroma is more likely to be situated along the area of lesser curvature of the aortic arch, we hypothesize that this difference in the course might explain the difference in stroke rate between the 2 approaches.

Overview

The transradial approach (TRA) is being employed more frequently for catheter-based coronary procedures, but the difference in the incidence of periprocedural stroke with the transfemoral approach (TFA) vs the TRA has been a matter of debate. Data from real-world registries have associated the TRA with a reduced risk of periprocedural stroke, but randomized controlled trials have failed to demonstrate this difference.^1,2 The risk of stroke occurring with either the TFA, the LRA, or the right radial approach, has been hypothesized to be due to catheter-related athero-embolic phenomena.³ Some studies suggest that catheters, during a right radial approach, while traversing the right brachiocephalic artery. theoretically may increase the risk of embolization into the right vertebral or the right carotid artery, in all patients, and the risk into the left carotid artery as well in patients with a bovine arch (25% of the population). The LRA has been postulated to not only offer an approach similar to the TFA but also, by bypassing the descending thoraco-abdominal aortic source of atherosclerotic plaque, lead to a decrease in descending aortic and iliofemoral embolization events.³ We hypothesized that, contrary to popular belief, based on the trajectories of catheter approach dictated by the 2 different anatomies, catheters being advanced to the heart via the TFA and the LRA take a widely diverging course along the arch of the aorta (Fig. 1). In the current paper, through real-life angiographic images, we describe the difference in the respective trajectories of these 2 catheter approaches and describe how these courses theoretically may impact stroke outcomes.

Figure 1.

An artist’s digital rendition of the arch of the aorta demonstrates the hypothesized approach dissonance between the left radial approach and the femoral artery approach. L-Radial, left radial; CFA, common femoral artery.

Description of Catheter Courses as They Relate to Aortic Arch Plaque Distribution

The divergent courses taken by the catheters with the LRA vs the TFA were seen during an intervention being undertaken for right coronary artery chronic total occlusion. A 7-Fr JR4 (Cordis, Miami Lakes, FL) catheter was used for the TFA, whereas a 6-Fr JL3.5 (Cordis) catheter was used for the LRA to engage the right and left coronary arteries, respectively, for simultaneous injections during chronic total occlusion percutaneous coronary intervention. A coronary angiogram was performed in the left anterior oblique 35' view at x17 magnification to allow a panoramic view of the aortic arch and a view of the course of the 2 catheters along the calcified arch outline. The TFA-mediated catheter, while it was being advanced to the heart, moved along the area of greater curvature of the aortic arch, whereas the LRA-mediated catheter was found to hug the area of lesser curvature of the aortic arch (Figs. 1 and 2). The widely diverging courses taken by these catheters may not have great impact on the technical aspect of the procedure, but their relationship to the distribution of atherosclerotic plaque in the arch of the aorta, at least theoretically, may impact the periprocedural stroke rates.

Figure 2.

Angiographic images of the arch of the aorta; the catheter advanced via left radial access (blue arrow) is hugging the area of lesser curvature, and the catheter advanced via femoral access (red arrow) is hugging the area of greater curvature.

Atheroma distribution in the arch has been shown to affect stroke risk. In a topographic analysis of the aorta, plaque located along the lesser curvature of the aortic arch when compared to other parts of the ascending aorta carried a 5-fold higher risk of stroke during coronary surgeries.⁴ The preponderance of atherosclerotic plaque deposition along the area of lesser curvature can be explained by the association between wall stress and plaque formation. The concept of shear stress being atheroprotective is not new and has been studied widely.⁵ To study this relationship between shear stress and the location of atherosclerotic plaque in the arch of the aorta, Soulis and colleagues measured the wall stress along the arch and found lower values along the area of lesser curvature of the aorta. In that study, they also found that the levels of low-density lipoprotein were elevated along the area of lesser curvature of the aorta.⁶ The combination of decreased wall stress and higher low-density lipoprotein clustering may explain the higher rate of atherosclerotic plaque formation along the area of lesser curvature of the aorta; this theoretically would contribute to an elevated stroke risk during manipulation along this part of the aortic arch.

Therefore, even though the major source of atherosclerotic plaque in the abdominal and descending thoracic aorta encountered during the TFA is obviously averted when the LRA is used, the course taken by catheters via an LRA may, however, tend to be more often along the area of lesser curvature of the aorta, which is the region of high atherosclerotic burden in the arch. Thus, this course may explain the counterintuitively comparable stroke rates occurring during coronary procedures performed via the TFA vs the TRA, as well as a surprisingly higher than expected stroke rate during percutaneous axillary access for transcatheter aortic valve replacement, which is preferentially undertaken from the left arm.^1,2,7

Conclusion

Our case demonstrates that catheters that are advanced via the LRA to the heart may move along the area of lesser aortic curvature, whereas catheters being advanced via the TFA to the heart may move along the area of greater aortic curvature. Given that the bulk of the aortic arch atheroma is more likely to reside along the area of lesser curvature of the aortic arch, this difference in the approaches might explain the counterintuitively comparable stroke rates with the 2 approaches, and the surprisingly higher stroke rate during percutaneous axillary access for transcatheter aortic valve replacement. Close observation, prior arch imaging, cautious tip control, and use of a guidewire to avoid catheter contact with the lesser aortic curve all may be applied while using an LRA approach, to prevent stroke. This observation is hypothesis-generating, and larger studies inclusive of patients with different arch types need to be undertaken to shed further light on this difference in approaches in a variety of clinical scenarios.