A 63-year-old man with hypertension, diabetes, dyslipidemia, and a history of smoking had multiple admissions for unstable angina since 2015. Physical examination during the current admission was unremarkable, with no signs of heart failure. Left ventricular systolic function remained normal throughout his clinical course.

Angiography in 2015 showed severe proximal LAD and subtotal mid-RCA lesions, both stented. In 2019, he developed inferior STEMI; angiography revealed patent LAD stent and very late distal RCA stent thrombosis, treated with DCB. On current presentation, echocardiography showed normal LVEF, and noninvasive tests suggested recurrent inferior ischemia.

Coronary angiography demonstrated a patent LAD stent and CTO in-stent restenosis (ISR) at mid RCA with ipsilateral collateral flow from the RV branch to the PDA. Anatomical challenges included a proximal RV branch near the CTO cap, a nearly 90° CTO entry angle, a lesion length of ~60 mm, and distal bifurcation involvement. The CTO had a tapered stump with a visible microchannel. The J-CTO score was 2.

PCI was performed via single radial access with a 6F short-tip AL guiding catheter and Finecross microcatheter. 3D wiring with UB3 under orthogonal views; escalation to Gaia 3. Anchor ballooning in the RV branch improved support. The wire successfully crossed into the PLV. Predilation with a small balloon, followed by scoring ballooning. A Crusade dual-lumen catheter enabled Gaia 3 wiring into the PDA, which was predilated with a 2.5 mm balloon. IVUS revealed undersized and extensively malapposed stents contributing to ISR and prior very late thrombosis. High-pressure NC 3.75 mm ballooning improved expansion, though full correction was limited by the original stent size. A hybrid treatment strategy was chosen—DCB for both PLV and PDA (3.0×20 mm and 3.0×15 mm respectively, with DCB-assisted kissing), and DES reconstruction of the mid-to-proximal RCA using 4.0×38 mm and 4.0×20 mm stents delivered with guide extension support. Final IVUS confirmed optimal expansion and apposition without edge dissection. Final angiography showed TIMI 3 flow with no complications. At 9 months, angiography demonstrated patent RCA stents and positive remodeling at the PLV ostium.

This case illustrates that well-planned antegrade CTO-ISR PCI through single radial access can achieve successful revascularization in complex restenotic anatomy. Maintaining the guidewire within the stent architecture is crucial when treating ISR-related CTOs. Intravascular imaging plays a pivotal role in identifying the mechanism of stent failure—here, significant malapposition and undersizing. Adequate lesion preparation is essential before DCB therapy, and a DCB–DES combination can be an effective strategy for complex bifurcation ISR while minimizing additional metal burden.