Overview of the CTO crossing algorithms.
The Global CTO crossing algorithm (J Am Coll Cardiol 2021;78:840-853) has 10 steps:
1) dual angiography
2) careful angiographic review focusing on proximal cap morphology, occlusion segment, distal vessel quality, and collateral circulation
3) approaching proximal cap ambiguity using intravascular ultrasound, retrograde, and move-the-cap techniques
4) approaching poor distal vessel quality using the retrograde approach and bifurcation at the distal cap by use of a dual-lumen catheter and intravascular ultrasound
5) feasibility of retrograde crossing through grafts and septal and epicardial collateral vessels
6) antegrade wiring strategies
7) retrograde approach
8) changing strategy when failing to achieve progress
9) considering performing an investment procedure if crossing attempts fail
10) stopping when reaching high radiation or contrast dose or in case of long procedural time, occurrence of a serious complication, operator and patient fatigue, or lack of expertise or equipment.