In CTO procedures, which approach relies on collateral channels from the distal vessel to reach the occlusion?

• A. Antegrade
• B. Retrograde
• C. Both
• D. None

Answer: (B)

The concept being tested is how CTO PCI can be approached. The retrograde approach relies on collateral channels from a donor vessel to reach the distal side of the occlusion. Operators navigate these collateral pathways—often septal or epicardial collaterals—with a microcatheter and wire to arrive at the distal true lumen beyond the blockage. From there, crossing the occlusion proceeds from distal to proximal, and techniques like reverse CART may be used to connect the distal path with the proximal lumen and complete revascularization. This strategy is especially useful when the proximal entry is hard or when an antegrade crossing is unlikely or has failed. In contrast, the antegrade approach starts at the occlusion’s proximal entry and moves forward toward the distal lumen without relying on distal collateral pathways. Therefore, using collateral channels from the distal vessel to reach the occlusion is a hallmark of the retrograde approach.