Rethinking small vessel CTOs: collateral channels as a bridge to subsequent complex intervention-a case report.

Background: The retrograde approach has been integrated into global practice for managing challenging chronic total occlusion (CTO). A fundamental limitation of this technique is the requisite presence of navigable collateral channels. Thus, the incomplete exposure of collateral pathways renders complete interventional revascularisation of multi-vessel CTOs a persistent challenge. Case summary: A 53-year-old man was admitted for unstable angina. Coronary angiography demonstrated three-vessel CTOs, with a long right coronary artery (RCA) CTO, a proximal left anterior descending artery (LAD) CTO, and a CTO in a small-calibre left circumflex (LCX). A staged percutaneous coronary intervention (PCI) approach was adopted. The LAD and LCX CTOs were sequentially revascularized via an antegrade approach. Leveraging optimal visualisation of the collateral channels, particularly an interventional channel from the distal LCX to the RCA, a more challenging RCA CTO was successfully revascularized using a retrograde approach. The patient was symptom-free and was discharged 3 days later. Discussion: This case highlights the presence of potential interventional collateral channels in a small vessel CTO, which may enhance the success rate of subsequent, more complex CTO interventions via a retrograde approach.