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Paraggio et al. Vessel Plus 2019;3:12 I http://dx.doi.org/10.20517/2574-1209.2018.72 Page 3 of 11
The above described score tools are very useful to guide clinical and procedural decision during CTO
procedures. In addition, they could be very helpful when planning complex PCI as they underlined all
angiographic and clinical predictors of every PCI technical success.

CAN COMPLEX PCI AND CTO PROCEDURES FIT TRANSRADIAL APPROACH?
In usual PCI setting 6F Guiding Catheter (GC) is enough to obtain a complete procedural success in the
vast majority of cases. However, CTO lesions could better be afforded using large (7F or 8F) GC in order to
obtain larger inner space together with higher back-up support and stability. In last decade, this strategy was
almost exclusively performed by transfemoral approach. However, the selection of radial arteries as vascular
access for complex PCI has substantially grown in the last ten years as several studies have demonstrated
[18]
a marked reduction of access site-related bleedings . Recently, several technical improvements in PCI’s
materials have boosted utilization of radial approach even in more complex interventions, such as CTO
procedures, also adding the option of hybrid vascular approach (6F radial access for contralateral injection
[19]
and 7F or 8F for antegrade/retrograde approach) . First, a new family of GC, called “Sheathless” (first
available type: Eucath, Asahi, Japan), has been introduced. The “Sheathless” GC has a highly hydrophilic
coating and can be inserted without a sheath thus showing an increased inner lumen when compared to
standard GC (6.5F vs. 6F or 7.5F vs. 7F). More recently, a brand-new sheath, called “Slender” (Terumo, Tokyo,
Japan), has been produced and showed an increased inner lumen despite an outer diameter still in the range
of radial compatibility. Therefore, in the setting of complex PCI, a 6-in-7 F “Slender” sheath could be easily
used to insert a 7F GC into radial artery thus combining technical feasibility with lower vascular access
related complications.

The development of such devices have progressively make radial approach more common during CTO
procedures. Indeed, in such procedures, the need for larger GC is essential as only two microcatheters or one
microcatheter and a monorail balloon fit together into 6F GC, while all frequently used devices can be only
inserted alone.

In the setting of CTO intervention and more extensively in all PCIs, material compatibility is a critical issue
and operators should focus their attention on materials’ compatibility, considering also that same material
(for example same size of semi-compliant balloon) of different manufactures may have different diameter.
Therefore, a careful procedure planning which includes a tailored selection of radial equipments may help
safely carry on PCI through radial approach.

GUIDING CATHETER AND MOTHER-IN CHILD DEVICES: THE NEED FOR MORE SUPPORT
When planning a PCI, one of the first thing to decide is the GC you would use to obtain enough backup
and support to perform the procedure. In the setting of CTOs, a large (7 or 8 F) GC offers more support
and greater inner diameter which allows insertion of such complex materials, even in combination (such as
dual over-the-wire microcatheters) and now can be inserted by radial approach. In last few years, several
techniques and materials have been developed to increase procedural support to overcome difficulties
encountered in crossing CTO or complex lesions and delivering PCI materials.

Nowadays, the need for more support in CTO procedures could be afforded by two different strategies: usage
of devices with improved backup force (“passive support”) or techniques to directly enhance support (“active
support”).

The better way to enhance passive support is to choose a larger GC with more supportive backup curves.
Therefore, Amplatz left GC for the right coronary artery and XB (eXtraBackup) or EBU GC for the left
coronary artery are commonly used to improve backup. In order to avoid such complications, side holes are