Is Epicardial Collateral Dilation as Out-of-Bounds Terrain during a Retrograde CTO Approach? A Case Report

The retrograde approach in chronic total occlusion (CTO) percutaneous coronary intervention (PCI) through epicardial collaterals (ECs) is a more challenging procedure. When the EC is the only feasible interventional vessel and the microcatheters (MCs) cannot cross it, controlled dilation using a small balloon may facilitate MC crossing. Herein, we present a 69-year-old female patient with severe in-stent restenosis of the left main artery (LM) to ramus branch, as well as ostial in-stent reocclusion of the left anterior descending artery (LAD) and the left circumflex artery (LCX). PCI strategy for treating the LM-LCX lesion was attempted but failed via antegrade approach. Tip injection through corsair MC confirmed the feasibility of epicardial collaterals from the posterior descending branch of the right coronary artery (RCA-PD) to the LCX. However, neither the 2.6F Corsair MC nor the 1.8F Finecross MC could pass through the tortuous segment of the retrograde epicardial channel, even though the SUOH03 guidewire passed smoothly. Subsequently, the collateral vessel was pre-dilated with a 0.8×10 mm balloon at a low pressure near the uncrossable segment. Thereafter, the 1.7F Instantpass MC smoothly passed through the epicardial collateral. The routine procedure was successfully performed using a drug-eluting stent (DES) in the proximal LCX and drug-coated balloons (DCBs) in the distal segment, resulting in good blood flow. This case demonstrates that controlled small balloon dilation of the EC may facilitate MC crossing during the recanalization of more complex CTO lesions.