Retrograde Revascularization of Left Main Coronary Chronic Total Occlusion: Distinct Roles of Conus Branch and Septal Collaterals: Two Case Report

Abstract

Introduction: Chronic total occlusion (CTO) of the left main coronary artery (LMCA) is exceedingly rare and represents one of the most demanding percutaneous coronary interventions (PCIs) due to the large ischemic territory involved. This report describes two unique LMCA CTO cases successfully treated via distinct retrograde collateral routes, one through the conus branch artery (CBA) and another through septal collaterals, highlighting the technical feasibility of individualized pathway selection in situations where antegrade wiring is not possible. Patient Information and Clinical Findings: Case 1: A 65-year-old woman with Canadian Cardiovascular Society (CCS) class III stable angina and isolated ostial LMCA CTO supplied by the CBA from the right coronary artery (RCA). Diagnostic Assessment, Intervention, and Outcomes: In both cases, diagnostic angiography precisely mapped collateral pathways enabling retrograde revascularization. Contemporary guidewires, microcatheters, and drug-eluting stents (DES) were used to restore distal flow. Successful retrograde PCI was achieved with final TIMI 3 perfusion and complete resolution of angina. On scheduled follow-up (1 week, 1 month, 3 months), both patients remained asymptomatic with normal electrocardiogram (ECG) and preserved left ventricular function [left ventricular ejection fraction (LVEF) case 1: Fifty-five percent, LVEF case 2: Fifty-five percent]. Conclusions: These cases demonstrate that careful identification and utilization of collateral anatomy, particularly the conus branch and septal channels, can allow safe and effective retrograde revascularization of LMCA CTO when standard antegrade PCI is unfeasible. Understanding distinct collateral patterns expands treatment options for high-risk, CABG-refusing patients and supports the role of tailored retrograde strategies in complex coronary interventions.