How to cross a collateral with a microcatheter after guidewire crossing

Step-by-step description of potential solutions when the retrograde wire crosses a collateral but the microcatheter fails to cross. Microcatheter delivery can be facilitated by: (a) rotation; (b) increasing support with guide extension of side branch achoring; (c) changing microcatheter; (d) using a short (135 cm long) microcatheter; (e) using a new microcatheter; (f) dilating the collateral (septals only); (g) anchoring the retrograde wire with an antegrade balloon; and (f) exhanging the guidewire for a stiffer one.

If the microcatheter fails to cross despite the above maneuvers, one could (a) try to cross the CTO with the retrograde guidewire; (b) use the retrograde guidewire as a marker on the location of the distal true lumen; or (c) use another collateral or try antegrade crossing.