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Page 6 of 11 Paraggio et al. Vessel Plus 2019;3:12 I http://dx.doi.org/10.20517/2574-1209.2018.72

Table 2. Main characteristics of chronic total occlusion guidewires commonly used in daily percutaneous coronary interventions
Shaft Tip Tip
Family Guidewire Tip weight (g) Main purpose
coating coating diameter
Fielder Fielder XT-A Polymer jacketed Hydrophilic 0.010 1 Sliding of
(Asahi) (tapered) microchannels
Fielder XT-R Polymer jacketed Hydrophilic 0.010 0.6 Sliding of
(tapered) microchannels
Sion Sion Hydrophilic Hydrophilic 0.014 0.7 Navigation of
(Asahi) tortuous vessels
Sion Black Polymer Hydrophilic 0.014 0.8 Surfing of small vessels
jacketed (collaterals)
Sion Blue Hydrophilic Hydrophobic 0.014 0.5 Higher torque control for
vessel wiring
Sentai Fighter Polymer Hydrophilic 0.009 1.5 Sliding of
(Boston Scientific) jacketed (tapered) microchannels
Hornet Hydrophilic Hydrophilic 0.008 1 Navigation of
(tapered) microchannels
Samurai Hydrophilic Moderated 0.014 0.5 Higher torque control for
Hydrophilic vessel wiring

A correct manipulation of CTO guidewires should always be performed using an over-the-wire system such
as microcatheters. Main characteristics of such devices are summarized in Table 3. Among these, Finecross
(Terumo, Tokyo, Japan) and Corsair Pro or Caravel (Asahi Intecc, Japan) are the most commonly used.
The key role of microcatheter in CTO procedures could be summarized in three essential steps: (1) to safely
place CTO guidewire just in front of the lesion; (2) to increase support and precision in CTO guidewire
manipulation during antegrade crossing; (3) to allow guidewire exchange once the lesion has been crossed.
All these steps could be used even in complex PCI procedures when a CTO dedicated guidewires is used to
cross a heavy calcified and/or narrowed lesion as explained before or when a workhorse guidewire should be
manipulated more precisely with facilitate torque in the tip response. Finally, microcatheters could be very
useful to reduce guidewire kinking and prolapse while trying to cross a lesion immediately after a large side
branch.

More recently, dual lumen microcatheters, such as Fineduo (Terumo, Tokyo, Japan), Crusade (Asahi
Intecc, Japan), Twinpass (Vascular Solutions, USA) and NHancer RX (IMDS, The Netherlands), with both
a rapid exchange and over-the-wire lumen, have been developed. During CTO procedures, dual lumen
microcatheters are useful in some scenarios: (1) to allow a more precise engagement of the cap located at
the level of a side branch (in antegrade approach) or located too close to the connection with interventional
collateral (in retrograde approach); (2) to preserve side branch when a bifurcation is located into CTO body;
(3) to perform “parallel wire” technique. In everyday practice, the employment of dual lumen microcatheters
is increasing, as they could be very useful in bifurcation PCI to wire a side branch with difficult take-off
angle or to re-wire side branches after crossover stenting . Moreover, in any case of main vessel dissection
[23]
without a protection guidewire into side branch during bifurcation PCI, a dual lumen microcatheter
could help to wire the side branch limiting the risk of dissection expansion after second “free” guidewire
advancement.

BALLON UNCROSSABLE AND BALLOON UNDILATABLE LESIONS: PUSHING THE LIMIT
[24]
After successful guidewire crossing, in 5%-10% the microcatheter is not able to cross CTO body . This
will usually occur in the highly calcified lesions, which are also challenging to cross with guidewires;
however, even in simpler cases, this problem could arise unexpectedly. In this setting, some techniques may
be adopted to increase support, such as “buddy wire”, the employment of a mother-in-child system or the
anchoring balloon technique, with uncertain results. In the past, in case of persisting uncrossability, the
first widely used option was “grenadoplasty” (during which a small balloon is advanced as far as possible
and then inflated at high pressures until it ruptures), with conflicting results in plaque modification.