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Page 2 of 7 Dobric et al. Vessel Plus 2019;3:26 I http://dx.doi.org/10.20517/2574-1209.2018.77
[3-5]
during coronary angiography, with a prevalence rate of 18%-52% .

CTO remain the most challenging lesion subset in patients undergoing percutaneous coronary
interventions (PCI). It was early recognized as one of the most important obstacle in achieving complete
revascularization in patients with multivessel coronary artery disease. Even the father of interventional
cardiology Andreas Gruentzig noted in an interview in 1985 (two weeks before his tragic passing in an
airplane crash): “The total closure is a real problem, if we cannot solve the total closure problem, we
[6]
probably will never really address the question of multivessel disease dilatation” .

Myocardial territory distal to CTO is usually supplied by collateral flow, which is sometimes sufficient to
preserve viability and contractile function in resting conditions. On the contrary, collaterals are most often
not sufficient to provide adequate blood flow during increased demands, providing adequate protection
[7]
against ischemia in only 5% of patients . This means that collateral vessels cannot fully substitute the
function of open epicardial artery, which constitutes the rationale for performing PCI for CTO.

Regarding the prognostic impact of coronary artery bypass grafting (CABG) for CTO revascularization,
this issue is lacking high-quality randomized data. Isolated CABG for an isolated CTO of the LAD (or other
coronary arteries) cannot be justified on the basis of preventing future events compared with either medical
[8]
therapy or PCI. CABG for CTOs will often be part of a strategy of offering complete revascularization .

Technical aspects of the PCI for CTO
Although PCI for CTO remains most challenging for many interventionalists, we are witnessing gradual
improvement in all procedural aspects during last decade. For experienced operators, procedural success
rates could reach > 90%, which is the result of improvements in instrumentaria, better training, increasing
operator expertise with complex techniques, and spreading the knowledge through the work of dedicated
CTO organizations, such as EuroCTO club and others [9-12] .

[2]
Many technical factors should be taken into consideration while planning PCI for CTO . In general, ad
hoc PCI for CTO is not encouraged; instead, staged, elective, and carefully planned approach is preferred.
When dealing with selection of arterial access site, most dedicated CTO operators prefer to use femoral
artery for targeting occluded artery, since it allows them to use larger size catheters (7 or 8 French)
which offers better passive support and more space for simultaneous insertion of devices. Radial artery
is most often used to cannulate non-CTO artery in order to visualize occluded artery distal to the place
of occlusion via collateral circulation. Dual injection should be used whenever possible, since it allows
operator to appropriately asses morphologic characteristics of the occluded segment. Selection of coronary
guidewires is critical step for the successful PCI of CTO. Many characteristics of the guidewires should be
taken into account when selecting appropriate guidewire like: polymer cover, wire coating, core material,
and tip stiffness. Operators may choose between wires depending of what they need most in every phase
of intervention: more torque control, more maneuverability, more penetration power, less potential to
damage collateral channels, reentry etc. Microcatheters are devices that are almost always used in PCI for
CTO. They offer the operator possibility to exchange guidewires rapidly, provides additional support for
the guidewire, provides protection of collateral vessel, provide route to inject small amount of contrast (“tip
injection”) to visualize distal vessel or collaterals. Many improvements in manufacturing technology give
us wide array of available devices that meet different needs of operators in various situations. Contralateral
contrast injection is frequently needed to precisely and safely navigate guidewire toward vessel distal to
occlusion, and we strongly recommend using it whenever distal vessel cannot be adequately visualized via
ipsilateral dye injection.