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When size matters: Feasibility of using larger diameter radial catheters

Abdulla Damluji MD, MPH, Ian C. Gilchrist MD, FSCAI
Pioneer transradial angiography (TRA) in the 1940s was thwarted by the engineering limits imposed by the available primeval 8- to 10-French catheters that were passed into the radial artery and the resultant arterial spasm and thrombosis [1]. By the 1990s, 5- and 6-French catheters were becoming a reality and resurrected radial artery catheterization as a viable procedure. Much attention has been focused on the limited published population studies that show mean radial artery diameters well within the comfort parameters required for common 5- or 6-French procedures. In the push to spread the transradial technique, a false perception of a 6-French size limit has become prevalent despite population studies that show that these arteries are at times anatomically suitable for larger devices, and small case reports demonstrating successful use of larger device. True, a vast majority of routine procedures can be done using 6-French or smaller, but at times a larger diameter could make the procedure easier and perhaps better. To date, there has been a paucity of modern published experience.
In this issue, Coroleu et al [2], described 60 patients who underwent complex coronary and carotid transradial procedures using 7- or 8-French sheath catheters. The results of this study are promising with >98% of all coronary and carotid cases successfully completed and very low short- and long-term post-procedure complications. This high success rate may reflect a large selection bias as the report reflects a case series. To identify arteries that can accommodate larger sheaths, the authors performed a pre-procedural manual palpation to evaluate flow and collateralizations. Alternatively, some radial operators have reported using duplex-ultrasonography to measure the radial artery diameter and its ratio to the sheath diameter [3, 4]. The present authors used a confirmatory forearm angiography before committing to a larger sheath. This approach has the added advantage of allowing identification of tortuousity and strictures in the upper extremity that might limit the use of larger catheters.
Other factors deserve a mention and consideration in this special cohort. First, most patients were men who were most likely larger, with bigger vessels, than women. Second, ethnicity of the patient population was not described, but most likely relatively uniform and not representative of other ethnicities. Third, the operators and catheterization laboratories were highly experienced and successful in transradial techniques and similar results might not be reproducible in less experienced centers. Fourth, the majority of the procedures were performed in elective settings and applicability in emergent settings might be a challenge. Finally, 10% of patients had asymptomatic radial occlusion with adequate collateralization. Thishigher than typical radial artery thrombosis rate may be due to larger sheath size, but little information was provided about hemostasis technique and whether ?¢????patent hemostasis?¢???? was used to optimize hemostasis [5].
The techniques of performing successful TRA continue to grow and contribute to its improved patient outcomes and satisfaction. Larger diameter catheters can play an important role in successful transradial procedures. The potential for a radial artery to accept a sheath larger than 6 French should not be forgotten if the need for a larger lumen catheter arises. However, the expertise of the operator and selection of appropriate target population for such intervention is vital to maintain a high success rate and low short- and long-term complications. Further work is needed to understand how best to minimize radial artery occlusion as a long-term sequelae as TRA continues its growth in popularity.

Catheterization and Cardiovascular Interventions
Volume 79, Issue 4, pages 601-????602