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Colombo et al. Vessel Plus 2019;3:29 I http://dx.doi.org/10.20517/2574-1209.2019.005 Page 3 of 9

• Reversal of anticoagulation with protamine is not recommendable in perforations occurring during
CTO interventions since it does not solve the mechanical problem underlying this complication and, on
the other hand, it can dramatically increase the risk of thrombosis until all equipment are in coronary
arteries.
Specific approach: different devices and techniques can be used in relation to the perforation site.

[8]
Coronary perforation have been classified by severity according to Ellis criteria . Ellis classification
recognizes 3 grades of perforation severity (I, II and III): while grade I can occasionally resolve without
intervention or just with reversal of anticoagulation, the grade III is usually referred to abrupt and large
perforations with acute cardiac tamponade and hemodynamic instability and may cause myocardial
infarction and death.

Nevertheless anatomic classification based on vessel location of perforation can be more helpful, orienting
in the management approach. It distinguishes three types of CPs: main vessel (MV) perforation, distal
[9]
target vessel perforation and collateral channel perforation .

MV perforation occurs in either antegrade or retrograde approaches. Guidewire perforation during
wire escalation or dissection and re-entry techniques are typically self-limited and rarely lead to cardiac
tamponade. The risk of pericardial effusion dramatically increase when a device (i.e., microcatheter or
TM
Crossboss ) or a balloon is advanced along a guidewire located in the pericardial space, outside the
architecture of the vessel. The first highly important step is represented by prompt balloon inflation
proximally to the area of contrast extravasation. If extravasation persists despite prolonged balloon
inflation, then a covered stent should be implanted. Covered stent implantation generally requires a
dual catheter technique (“ping-pong”) in order to minimize bleeding. While a balloon is maintained
inflated through the first guiding catheter, a second catheter is advanced near the coronary ostium and
covered stent is positioned proximal to the occluding balloon. Then the occluding balloon is deflated and
withdrawn and the covered stent is advanced and deployed. Covered stents advancement can be difficult in
tortuous and calcified vessels due to the lack of flexibility of these devices. In the same way operators must
take into account that their delivery across not well prepared CTO lesions should be demanding.

Distal target vessel perforation typically represents a complication of antegrade approach, occurring after
CTO crossing. It is usually due to advancement of stiff and/or highly hydrophilic wires into small branches.
Dual arterial injection could help to prevent this type of complication, showing vessel anatomy beyond the
distal cap of the CTO. Also in this case, prompt balloon dilatation proximally to the perforation site is the
first treatment step. If bleeding persists , embolization with coils, fat, microsphere/beads or thrombine is
required. In our experience coils release through common microcatheter (i.e., FinecrossÔ, Terumo) is the
safer and more feasible option. We prefer detachable coils that allow a more accurate placement.

“Balloon-Microcatheter Technique” (BMT) using microcatheters compatible with 6 Fr guiding catheters
can be used for treatment of this type of perforation. The BMT consists of simultaneous advancement of a
microcatheter over a parallel wire distal to the occluding balloon, in order to continue to operate through
the microcatheter itself without deflating the occluding balloon . This technique is able to accurately
[10]
assess sealing of the perforation before and after the release of microcoils by tip injections from the jailed
microcatheter, with no need of repeated deflations of the the proximal occluding balloon.

Collateral vessel perforation is a unique complication that may occur during retrograde CTO PCI. It is
usually due to guidewires and/or devices advancement through the collateral or to balloon collateral
dilation performed in order to facilitate retrograde devices passage. Progression to cardiac tamponade
will depend on the location of the collateral vessel (i.e., septal vs. epicardial). Septal collateral perforation