Access Route and Guiding Catheters
Although radial approach is feasible, 90 % of experienced operators prefer femoral access mainly because they are used to it and because this access allows for use of larger guiding catheters. For chronic occlusions a good passive support with coaxial alignment and sufficient lumen to host several wires, an anchor balloon and a microcatheter or Corsair or even sometimes intravascular ultrasound (IVUS) guidance is crucial. This can only be achieved with larger guiding catheters (7 and 8 French [Fr]). For the left coronary system extra backup-type catheters (Voda left, extra backup, geometric left, left support) are preferable. For the right coronary artery we prefer left Amplatz 0.75-2.00 shapes, hockey stick upon gentle superior origin of the right coronary artery (RCA), Judkins shape for slightly inferior origin and internal mammary artery (IMA) or Shepherds Crook Replacement (SCR) type guiding for upward origin of RCA. For the RCA I strongly recommend guides with side-holes to prevent aorto-ostial disssections or progressive spiral dissections caused by forceful dye injection into a subintimal space.
It is absolutely mandatory to visualise the vessel distal to the occlusion to avoid blind poking or immensely dangerous dilatation of a false wire exit. When the distal vessel is not filled by orthograde collaterals or these collaterals disappear during manipulation, contralateral injection is a must. The contralateral approach can also be achieved easily by puncturing the same groin with a 4-6 Fr catheter, which may overcome an operators inhibition to insert a second sheath in the other groin.
Over the wire kink resistant microcatheters ease wire manipulation and allow atraumatic rapid exchange or reshaping of the wires and its use is therefore strongly recommended.
Wires and Handling
The most popular current strategy is to start with the atraumatic tapered and highly lubricious Fielder XT, which according to the EuroCTO registry will be successful in 39 % of cases. The second most popular selection - especially in old and calcified occlusions that are not very tortuous is to select stiffer tapered wires, like the Confianza 9 Pro« early in the process to minimise the risk of large dissection as well as shorten and simplify the procedure. Another recent line of action is to start with a soft tapered polymer wire (e.g. Fielder XT), stepping up quite early (Con anza 9 Pro or Miracle 6g) and then step down to a softer wire again.
The three fundamental elements of wire handling are rotating, pushing and pulling the wire. 
It is important to feel the resistance at the wire tip, when pulling the wire, since a wrong channel often exerts much higherresistance than the correct lumen. Any wire has the tendency to follow the outer part of the vessel curve, which can often cause the tip to exit the lumen. It is therefore preferable to direct the wire-curve towards the inner part of the vessel bend.
Parallel Wire Technique
First described in 1995 this is still the best technique to correct a false wire position.24 If the first wire has entered a false lumen, it is left in place to mark the dissection channel and a second wire (typically the same stiffness or stiffer and often tapered) with a slightly different tip curve to allow creating a slightly different course supported by an over-the-wire (OTW) (balloon) catheter, is passed along the same path parallel to the first wire, with care taken to avoid wire twisting. This technique allows for penetration towards the distal cap more centrally, avoiding the false channel that is marked by the wire left in situ. Occasionally, three or more wires are used in parallel.
How to Overcome Specific Challenges Tortuous Access
The most common approach for CTO-PCI is via the groin. However, in some elderly patients catheter manipulation via femoral approach is barred by tremendous friction due to severe kinking of the iliac artery, most probably because of atherosclerotic vessel remodelling.25 A common solution is to use a larger rigid kink resistant long sheath with a stiff guidewire. Nevertheless in rare cases the kinking cannot be overcome and the friction remains high that the investigator has to puncture the contralateral side or switch to a transradial approach, which might be extremely difficult as well because the atherosclerotic disease is often generalised, and last but not least in more than 70 % of the cases we do need two arterial catheters for contralateral injections. Finally up to 1 % of the CTO procedures may fail because of insurmountable access problems.
Inserting two parallel sheaths and extra stiff guidewires into the same common femoral artery is a simple novel technique not only to ease contralateral access but also to overcome serious iliac tortuosity that otherwise prevents diagnostic or therapeutic percutaneous interventions.
With this technique the external and common iliac will be straightened impressively and the friction reduced tremendously thus enabling easy guiding catheter manipulations and intervention (see Figure 2A and B).26