Transradial Complex Coronary Interventions: Expanding<br />
the Comfort Zone

Rotational coronary atherectomy can be utilized for maximal plaque debulking or for a less aggressive strategy of lesion modification. The early recommended burr-to-artery ratio of 0.75–8, which was deemed to achieve a delicate balance of maximal debulking without causing undue burr-related vessel trauma, has been challenged. In the CARAT study,¹ a lesion modification strategy (burr-to-artery ratio < 0.7) was compared with a more aggressive lesion debulking strategy (burrto- artery ratio > 0.7) in a prospective multicenter, randomized trial. The findings of the 222 patients from 6 centers showed similar endpoints of final diameter stenosis, inhospital clinical complications and target lesion revascularization at 6 months between the two strategies. The acute angiographic complication rate immediately after atherectomy, however, was higher in the lesion debulking group. Lesion modification works by releasing the circumferential constraints, thereby improving plaque compliance. This allows for subsequent balloon expansion while avoiding the potential vessel trauma of a larger burr.
Lesion modification also allows for the use of smaller guide catheters. With the availability of large-lumen guides such as the RunWay^™ (available in 6 Fr only), Mach1^™ (6–8 Fr) (Boston Scientific Corp., Natick, Massachusetts) or the Launcher^™ (6–8 Fr) (Medtronic, Inc., Minneapolis, Minnesota), the smallest sizing of the guiding catheter based on burr diameter is as follows: none for 5 Fr; 6 Fr for 1.25–1.75 mm burrs, 7 Fr for 2.0 mm burrs; 8 Fr for 2.15–2.25 mm burrs; and 9 Fr for 2.38 mm burrs. In a study using ultrasound evaluation, the ratio of the inner diameter of the radial artery/outer diameter of the sheath of < 1 predicted severe flow abnormalities after transradial coronary intervention,² and the ratio of < 1 occurred more often with 8 Fr guides compared to smaller catheters. In another study comparing the smaller guides, the authors found no clear advantages in using the 5 Fr catheters compared to the 6 Fr with a higher crossover rate likely due to support issues.³ The optimal size of guide catheters in the transradial approach, therefore, appears to be 6- and 7 Fr, as were chosen in the current study by Egred et al.⁴
Anatomic variants of the radial artery may be a major factor for access failure in the transradial approach. Radial artery variations are quite common with ranges from 9.6–22.8% in two prospective examinations of patients undergoing coronary interventions.^4,5 These may include tortuous configuration, stenosis, hypoplasias, radio-ulnar loop and abnormal origin. Routine use of preprocedural ultrasound or angiographic assessment of the radial artery prior to access may avoid this potential pitfall.
Other specialty devices are also candidates for the transradial approach with 6- or 7-Fr guide catheters. Devices such as the Tornus penetration catheter (Abbott Vascular, Santa Clara, California), the Frontrunner^® microdissection catheter (Cordis Corp., Miami, Florida), distal protective filters devices, aspiration and rheolytic thrombectomy devices (Possis, Minneapolis, Minnesota), and the specialty coronary guidewires are all compatible with the largerlumen 6- and 7 Fr guides and can be used in the transradial approach. As suggested by the Egred et al article, transradial percutaneous coronary interventions are no longer reserved only for simple lesions. The benefits of early ambulation, patient comfort, early discharge and lower cost offered by the transradial approach can be expanded to the more complex lesion types.