Ask the Transradial Expert

Larger Catheters in Smaller Arteries: Overcoming Obstacles

Orlando Marrero, RCIS, MBA, Tampa, Florida, Zaheed Tai, DO, FACC, FSCAI, Winter Haven Hospital, Winter Haven, Florida, and Heart of Florida, Davenport, Florida

Orlando Marrero, RCIS, MBA, Tampa, Florida, Zaheed Tai, DO, FACC, FSCAI, Winter Haven Hospital, Winter Haven, Florida, and Heart of Florida, Davenport, Florida

Editor's Note: This version of the article has been altered from the original print version. Figure 1B has been corrected.

Question: Have you used the Terumo Slender Sheaths or the Eaucath (Asahii Intecc) when you use a 7 French via the radial approach? Is there an advantage to either one? 

Answer: We have used both sheaths in our lab. The following is a case example using the 6/7 Glidesheath Slender from Terumo. We also discuss the differences between the Glidesheath Slender and the Eaucath.

Case presentation

A 50-year-old male presented with a history of diabetes, hypertension, hyperlipidemia, and coronary artery disease. He had a previous myocardial infarction (MI) in 2010 with report of a right posterior descending artery (RPDA) occlusion and an ejection fraction (EF) of 45%. He then had another MI in 8/2013 with percutaneous coronary intervention (PCI) of his left anterior descending coronary artery (LAD) at another facility with a 3.0 mm x 23 mm bare-metal stent. His EF was reported at 35% at that time by ventriculography and no post procedure echo was performed. For the past 6 months, he had been having symptoms of intermittent chest pain and dyspnea on exertion that had become progressively worse. He subsequently had a stress test done with a reported EF of 24% and anterior wall ischemia. As a result, he was referred for cardiac catheterization. 


The right radial artery was accessed with a 5/6 Glidesheath Slender sheath (Terumo). A Judkins Left (JL) 3.5 was used to engage the left system, and a Judkins Right (JR) 3.5 was used to engage the right system and perform ventriculography.

The mid LAD was 100% occluded in-stent and reconstituted distal to the stent (Figure 1A-B). There was a small 1.5 mm diagonal with some diffuse disease involved. The left circumflex (LCX) artery arose normally and was a non-dominant vessel. There was a 50% stenosis prior to the takeoff of the marginal branch. The right coronary artery was a dominant vessel. A mid 40-50% stenosis was present, and distally gave rise to the posterior descending artery (PDA) and the posterior left ventricular branch (PLV). There was evidence of right-to-left collaterals to the apical LAD (Figure 2). The estimated EF was 20-25%.

Given the angiographic findings, revascularization options were discussed with the patient, and he elected to pursue a percutaneous approach. We upsized to a 6/7 Glidesheath Slender sheath. A 7 French (Fr) Extra Back-Up (EBU) 3.5 guide was used (Medtronic) to engage the left system (Figure 3). Heparin was administered to an activated clotting time (ACT) >300. Using a 135 cm Turnpike support catheter (Vascular Solutions) and a Runthrough wire (Terumo), we advanced to the proximal cap and changed to a Fielder XT wire (Abbott Vascular) (Figure 4). The wire was able to penetrate the proximal cap (likely via a microchannel) and wire distally without difficulty. Wire placement was confirmed by injection. A 0.9 mm laser (Spectranetics) was used to perform laser atherectomy, with multiple runs at 80mJ/mm2 fluency and a frequency rate of 80Hz to debulk the vessel and restore luminal flow (Figure 5). A 3.0 mm x 15 mm AngioSculpt balloon (Spectranetics) was used to dilate the vessels. An optical coherence tomography (OCT) catheter (St. Jude Medical) demonstrated intimal hyperplasia to the bare-metal stent (Figures 6A-C). The distal vessel was estimated to be about 2.75 mm. After predilation, a 2.75 mm x 12 mm Promus Premier stent (Boston Scientific) was placed to cover the distal edge of the stent and the in-stent segment portion. It was overlapped with a 3.5 mm x 24 mm Promus Premier stent just covering the proximal ledge of the stent. Aggressive dilation was performed distally with a 3.25 mm Quantum balloon (Boston Scientific) and proximally with a 3.5 mm Quantum balloon, with a final excellent OCT and angiographic outcome (Figures 7A-B, 8). There was no evidence of edge dissection. The patient had TIMI-3 flow in the vessel without dissection, perforation, or embolization upon completion of the procedure, and was pain free. There was compromise of the small 1.5 mm diagonal with slow flow, but the patient had no chest pain or electrocardiogram changes. Given the small caliber of the vessel and the absence of clinical indicators of ischemia, we did pursue revascularization of the vessel. The patient was discharged home the following morning.   


Use of the transradial approach for coronary intervention continues to increase in the United States, as well as worldwide. Despite the fact that the radial approach is associated with less vascular complications, increased patient satisfaction, and more rapid mobilization, it is not always the preferred route, particularly for complex coronary interventions. One of the main limitations of the radial approach is guide catheter size, limited vessel size, and the radial artery’s tendency to spasm (which can further reduce vessel size). Saito et al previously demonstrated that the radial artery is smaller than 7 Fr in approximately 1/3 of males and 2/3 of women (29% and 60%, respectively).1 Yan et al demonstrated the mean internal diameter of the right radial artery is 2.38 ± 0.56 mm, varies with gender, and tends to be smaller in women.2 In addition, friction may increase spasm and result in procedural failure.2

The issue of friction has been addressed with the administration of a “radial cocktail” and hydrophilic sheaths. Many operators prefer larger guides (minimum 6 Fr) for complex coronary interventions. Often a guide larger than a 6 Fr is utilized to allow for more guide support, more complex techniques, and adjunctive therapies (atherectomy, for example). However, many adjunctive therapies and complex techniques can be performed via 6 Fr with some variation of the technique or use of smaller devices. 

To overcome the issue of large catheters in small arteries, a sheathless guide (Eaucath by Asahi Intecc) or the 6/7 Glidesheath Slender sheath (Terumo) can be used. The two sheaths, however, are not equivalent. The Eaucath does not require an introducer and the outer diameter (OD) of the 6.5 Fr and 7.5 Fr sizes are 2.16 mm and 2.49 mm, respectively, comparing favorably to a femoral 6 Fr sheath with an OD of 2.70 mm. The Eaucath does have a stiffer tip, so operators must be mindful of potential vessel trauma when engaging the coronary tree. It also comes in limited shapes. Therefore, if an available guide is not suitable, operators may have to downsize to a 6 Fr sheath if they feel the patient’s radial artery cannot accept a regular 7 Fr sheath.

The Terumo Glidesheath Slender allows for smaller access (2.79 mm OD) than a standard 7 Fr sheath (2.95 mm OD), but still introduces a larger sheath the length of the introducer, typically where the vessel is at its smallest. The introduction of the smaller sheath may reduce initial spasm compared to a standard 7 Fr system. The smaller diameter radial artery is typically more of a concern in females. In the 6 Fr system, a sizing advantage exists for the Eaucath, albeit a slight one, since most patients can accommodate a standard 6 Fr (see Charts 1-2). If ultrasound guidance is being used for access, then the radial artery size can be assessed prior to the procedure in order to choose an appropriate sheath based on that estimation. 

An alternative approach to both of these options is the “combo” technique.3 This technique utilizes the minimal introduction of 7 Fr into the artery. The guide is advanced and the sheath withdrawn, creating a sheathless system. The OD of 7 Fr guide catheters typically varies between 2.3-2.4 mm, depending on the manufacturer. 

Typically, we use an Eaucath when performing chronic total occlusion (CTO) revascularization and obtain one radial and one femoral access, or dual radial access, especially in females. The larger guides allow for easier exchange of multiple devices and added support. Occasionally, an Eaucath will be utilized in complex non-CTO intervention, although the vast majority of these are typically done via a 6Fr sheath. The 5/6 Glidesheath Slender is used for standard access in all radials and the 6/7 Glidesheath Slender in larger males (anecdotally, in patients >180 lbs) for complex interventions and CTOs, because of the larger guide selection (as opposed to the limited guides in EauCath line) afforded by this approach. We have routinely been using the Glidesheath Slender sheaths for tibial access (especially since we now size the vessel by ultrasound for access). This allows treatment of complex peripheral disease from a tibial access.


  1. Saito S, Ikei H, Hosokawa G, Tanaka S. Influence of the ratio between radial artery inner diameter and sheath outer diameter on radial artery flow after transradial coronary intervention. Catheter Cardiovasc Interv. 1999; 46: 173-178.
  2. Yan ZX, Zhou YJ, Zhao YX, Zhou ZM, Yang SW, Wang ZJ. Anatomical study of forearm arteries with ultrasound for percutaneous coronary procedures. Circ J. 2010; 74: 686-692.
  3. Patel T, Shah S, Pancholy S. “Combo” technique for the use of 7F guide catheter system during transradial approach. Catheter Cardiovasc Interv. 2015 Nov 15; 86(6): 1033-1040. doi: 10.1002/ccd.26119.

Disclosures: Orlando Marrero reports he is a consultant for Boston Scientific. Dr. Zaheed Tai reports the following: Terumo (proctor for transradial course), Spectranetics (proctor for laser course, speaker, advisory board member), and The Medicines Company (speakers bureau). 

Orlando Marrero, RCIS, MBA, can be contacted at 

Dr. Zaheed Tai can be contacted at