**7. Thin walled sheaths and Sheathless guides**

Small diameter of the radial or ulnar artery has been overcome with thinner sheaths. For example the Slender (Terumo) (**Figure 4**) 6F outer diameter is 2.46 mm versus 2.62 mm for standard sheath outer diameter and the Slender 7F drops the outer diameter from 2.95 down to 2.79 mm. The downside is kinking of the thinner walled sheaths especially if partly inserted into the artery.

#### **Figure 4.**

*Thin walled sheath, GLIDESHEATH SLENDER® Introducer Sheath – ©2020 Terumo Medical Corporation. All rights reserved.*

Sheathless guides (Eaucath system from Asahi Intecc Co Ltd. or Railway system from Cordis) have opened up radial access for smaller arteries. The OD of the 6.5Fr SheathLess Eaucath is 2.16 mm, similar to the OD of the 4Fr sheath at 2.00 mm. The OD of the 7.5Fr SheathLess Eaucath is 2.49 mm, similar to the OD of the 5Fr sheath at 2.29 mm. The passing of the sheathless guide requires special attention to withdrawing the dilator before entry into the aorta from the subclavian. One other option is the use of an inflated balloon in the tip of the guide prior to passing into the artery referred to balloon-assisted shealthless transradial intervention (BASTI) [28]. The challenge is the use of 0.014 wire for support versus 0.021 or 0.035 and, as with sheathless guides one other issue is over manipulation of the guide without a sheath could induce spasm.
