introducer sheath inserted over the guidewire. Alternatively, the modified Seldinger technique uses a short 21‐gauge bare needle with anterior‐only puncture technique. After puncture of the anterior wall of the radial artery, a 0.021" guidewire is advanced into the artery allowing removal of the needle and sheathing over the guidewire. A randomized trial showed the traditional Seldinger technique (through‐and‐through) to be a more reliable way to obtain radial artery access with greater success rates, shorter procedure time, and shorter time to gain access. Procedure related complications such as radial hematoma or radial artery obstruction were similar between the two approaches [24]. In the event of failed access, repeat procedures or attempts can be performed more proximally if required.
Table 3.1 Common diagnostic and guide catheter shapes for TRA.
| Universal diagnostic | Diagnostic | Universal guide | Guide (left) | Guide (right) |
|---|---|---|---|---|
| Tiger II (Tig) | Judkins left 3.5 | IKARI left | EBU/XB 3.5 | Judkins right 4.0 |
| Kimny | Judkins right 4.0 | MAC 30/30 | Judkins left | Amplatz right |
| Jacky | Kimny | Amplatz left | Amplatz left | |
| IKARI left | IKARI right |
Navigating common anatomical problems
Whilst various anomalies in radial, brachial, and axillary arterial circulation are common, knowledge of just three key anatomical variations is important as they determine most radial procedural failures outside of failure to puncture [25]. In the event of resistance to the 0.035" guidewire, early arm angiography should be performed. This allows identification of the radial artery origin and the nature of any cubital crossover for “high takeoff” radial bifurcation above the antecubital fossa (Figure 3.1a and b). Anatomical variations should be expected and frequently coexist (e.g. radial loop with accessory radial artery from apex of loop). Angiography helps mapping of connections within the antecubital fossa (to avoid tiny accessory radial branches and visualization of radial loops). We prefer using a hydrophilic 0.035" J tipped guidewire (“Baby J” ‐ Terumo) or occasionally a coronary wire (0.014") for safe and gentle wire manipulation through tortuous and potentially fragile upper limb arteries. With experience these hurdles can often be negotiated but when this is not possible, the asymmetrical nature of forearm vasculature leaves ipsilateral ulnar, contralateral distal or proximal radial access and the femoral approach as alternate options [26].
Figure 3.1 Anatomic variations present challenges to successful transradial access but can usually be overcome. (a) High bifurcation with minimal tortuosity but early evidence of spasm, (b) High bifurcation of radial artery originating in the axillary artery with marked tortuosity, (c) Normal origin of radial artery but radial loop with associated tiny accessory radial (remnant radial) from the apex of the loop. This association is very common and often the operator is unaware of this anatomy until upsizing from a small calibre diagnostic catheter to a larger bore guide catheter which induces spasm of this tiny vessel. (d) Spasm of a tiny accessory radial artery (with subtotal occlusion of the vessel). (e) Subclavian tortuosity in patient with previous bypass grafting. This necessitated angiographic mapping and use of a coronary wire to navigate and exchange for a stiff 0.035" wire inside the catheter to help with torque and manipulation for selective engagement. (f) RORSA: Retroesophageal right subclavian artery (also known as “arteria lusoria”) incidence of 0.5 –2.5% can make entry into the ascending aorta challenging.
High radial‐ulnar bifurcation (“high take‐off”)
High‐origin radial arteries (defined by their origin above the antecubital fossa) are the most commonly encountered radial artery anomaly occurring in 7% of patients undergoing radial angiography. These present problems during angiography due to their small caliber and often‐tortuous course making them prone to spasm. Nevertheless, using a coronary wire to navigate the segments and small hydrophilic coated catheters, the procedure can be completed successfully from the access site in over 95% of cases [25]. In the case of spasm due to inadvertent access through a tiny accessory radial branch (origin above cubital fossa), if a small catheter passes then a 0.035" exchange length wire can be postioned in the ascending aorta allowing exchange for a sheathless guide catheter (e.g. Asahi SheathLess Eaucath®). This technique can be very helpful for improving lubricity and facilitating coronary intervention where standard guide catheters will not travel and avoid the puncture of a second access site.
Radial artery loops
Arterial loops are a common cause of ipsilateral transradial failure even for experienced radial operators – mainly because very small diameter loops may not straighten after wire passage and can cause pain with increased procedural duration. Typically, loops involve a section of radial artery that travels back proximally towards the brachial bifurcation before heading down to the forearm. Navigating the loop is made more challenging by the invariable association with a recurrent (accessory) radial artery (Figure 3.1c), which typically is a small caliber vessel with a straight path up the arm from the apex of the loop. After arm angiography, small loops can usually be navigated with a coronary wire or a steerable hydrophilic wire into the brachial artery. Wire passage alone may straighten the loop, or small calibre (i.e. 4Fr or 5Fr) may be exchanged allowing passage of a 0.035" wire with gentle traction allowing the loop to be straightened permitting the case to be completed in over two thirds of cases [27].
Tortuous Radial Arteries
Radial tortuosity defined by the presence of a bend of more than 90° in the contour of the vessel occurs in around 2% of cases and is often associated with severe spasm [28]. With any resistance to wire passage, the vessel should be mapped using angiography. We prefer crossing these with a coronary wire as they provide greater feedback and safety than a hydrophilic 0.035" wire. After wiring, the operator may use balloon assisted tracking (BAT) or catheter assisted tracking (CAT) to avoid the “razor” effect of a sharp leading edge causing subintimal injury dissection and spasm (Figure 3.2). This technique can help to deliver larger guide catheters in challenging anatomical situations including severe tortuosity, resistant spasm, small caliber radial artery and complex loops [29].
