The Second Access Site
Within the hybrid algorhythm the second access site allows contra-lateral coronary injections for visualisation of the target for AWE and ADR techniques and a 6F system will suffice. However adopting a retrograde approach either as a primary strategy or bail-out for failed antegrade approach requires a capability for passage of guidewires, microcatheters and balloons into the donor vessel (giving rise to septal or epicardial collaterals). 6F is a minimum but 7F has advantages of better contrast delivery, better passive support and importantly the ability to use a wider range of equipment and techniques. (see Table 1) It is therefore evident that the selection of 6F guide catheters may profoundly limit some of the potential CTO techniques such that larger diameter guides are needed when more complex techniques are planned or anticipated. Recommendation of radial vs. femoral access for the second arterial site is also difficult due to the fact that no randomised data exists on transradial access in CTO PCI and all of the registry data is single centre or single operator derived and conducted by operators with specific experience in transradial PCI.21 Radial access therefore constitutes a valuable alternative to femoral access in CTO PCI in high volume radial centres, with anticipated equipment and techniques taken into consideration.
Radial vs Femoral Dominance
Promotion of a high volume of radial access may interfere with the equally important goal of maintaining proficiency in the femoral approach, which is indispensable in a variety of procedures. As with the radial approach, outcomes depend on the experience of operators and centres. Rafie et al. reported higher vascular access complication rates (12.5 %) when default radial operators in a single centre undertook PCI cases via the femoral approach.22 As expected, use of femoral access was associated with increased case complexity and larger arterial sheaths and femoral access was performed without fluoroscopic screening. In contrast, a recent multicentre study has demonstrated an extremely low incidence of vascular-access complications (0.89 %) in CTO PCI cases performed by default radial operators when femoral arterial access is performed using routine fluoroscopic guidance.15