**3. Principal approaches during CTO-PCI**

As shown in **Figure 2**, the principal factors on which the indication for revascularization of a CTO depends on comprise the following:


Considering these factors before CTO-PCI allows the estimation of the potential benefit for the patient, as well as the technical severity and risk being associated with the intervention. Using the so-called J-CTO-score reveals optimal graduation of the complexity of the CTOlesion itself and is more commonly being applied by experienced CTO operators [20].

The latest European guidelines for myocardial revascularization from the year 2014 [21] recommended a class IIa, with a level of evidence B ("*Percutaneous recanalization of CTOs may be considered in patients with suspected ischemia reduction in a corresponding myocardial territory and/or angina relief*."), and retrograde recanalization techniques are recommended only by a class IIB, level of evidence C ("*Retrograde recanalization of CTOs may be considered after a failed antegrade approach or as the primary approach for selected patients*.").

**Figure 2.** Indications for CTO-revascularization.

This lower recommendation class compared to the PCI of nonchronically occluded coronary lesions is in conflict to the nowadays very high success rates and low complication rates of CTO-PCIs being performed by experienced interventionalists. For instance, patients with prior CABG and a complex morphology of occluded native coronary arteries as well as consecutively occluded bypasses years after CABG surgery may benefit most from a technically demanding and long-lasting antegrade-retrograde but finally successful recanalization of native coronary arteries, as these patients may become free from limiting symptoms in daily life [22].
