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Page 6 of 9 Colombo et al. Vessel Plus 2019;3:29 I http://dx.doi.org/10.20517/2574-1209.2019.005

If no placed before, intra-luminal guide-wire should be promptly advanced and, if correct position is not
certain, a microcatheter should be used (laminar blood back-flow and eventually tip-injection can help to
confirm correct position). Also IVUS could be used to avoid intimal injection and confirm correct wire
position. Once intra-luminal wire position is confirmed, balloon inflation and stent implantation usually
resolve the dissection.

If sub-intimal, the wire should be left in its position and a second guide-wire should be placed distally
(“parallel wire”). Whether not possible, a re-entry technique must be considered.

Thrombus formation/embolization: during CTO PCI the activated clotted time (ACT) has to be controlled
every 30 min at least, to ensure correct anticoagulation. It must be maintained above 350 s. If ACT is low,
correct with heparin infusion. In cases of heparin-resistance bivalirudin should be considered. When
thrombosis occurs thrombus aspiration systems could be employed, followed by multiple balloon inflations
but this strategy could lead to distal embolization. Gp2b/3a infusion should be also considered.

Spasm: guiding catheters and guidewires could induce an incremented vasoreactivity. In these cases
intracoronary injection of vasodilators (es. Nitroglicerine, Adenosine, Nitroprusside) is recommended and
usually resolve the spasm.

Accidental air injection: this is a rare eventuality that ideally should never happen. Meticulous bleed back
from catheters and flushing after each device exchange should be practiced. Balloon rupture can also
introduce air in the coronary arteries, though in small quantities. When occurring, air aspiration is crucial
and could be combined to inotropic agents infusion. Is also possible to attempt bubbles breakdown with
wires/balloons.

EQUIPMENT LOSS OR ENTRAPMENT
Equipment loss or entrapment during CTO PCI (guidewires, stents and other devices) usually represent a
infrequent circumstance. Indeed it is a rarely reported complication so that its real incidence is unknown.
The risk for this complication is related to lesion complexity, extent of calcifications, vessel tortuosity and
techniques required for recanalization.

Knuckled wires have the potential of getting knotted. For this reason extreme caution should be paid when
retrieving them in order to avoid entrapment. Guidewire fracture may also occur but rarely is associated
with adverse clinical effects. Similarly microcatheters overtorquing could lead to entrapment.Balloon
entrapment in highly calcified lesions and tortuous vessels a balloon could occur. In some cases balloons
cannot be deflated for hypotube kinking. In both cases is crucial to remove the device avoiding distal
ischemic damage. A controlled traction on the device avoiding the system fracture should be applied as
first measure. If traction is not sufficient it would be necessary to advance a “guide extension catheter”.

When stent loss occurs, retrieval should be attempted in all cases by distal balloon inflation and withdrawn
together with the lost stent into the guide catheter. Not retrievable stent should be crushed against the
vessel wall by multiple balloon inflations and stent deployment. Finally, adequate lesion preparation, is
crucial to avoid stent loss during delivery attempt.

CONTRAST-INDUCED NEPHROPATHY
CTO PCI can be long-lasting procedures with administration of high volumes of contrast medium.
Accurate patient selection should be performed in order to identify those at higher risk of CIN (incidence
3.4%), carefully balancing the benefit-risk ratio of the procedure. Prevention of CIN is the first measure