Case Summary. We successfully treated a complex case whose syntax score was 40.5 with staged procedures. It is well known that collateral recipient vessels should be treated earlier than donor vessels. How- ever, in the settings of treating multiple chronic total occlusions, we should establish desirable situation to treat the most difficult lesion as easily as possible. Therefore, we sometimes treat collateral donor vessels than recipient ones. Although thick guiding guiding catheters are widely used to treat chronic total occlusions, narrow ones provide good performance even in the settings of retrograde procedures. TCTAP C-065 Challenging Re-attempting PCI to Proximal RCA-CTO Having Rich Bridge Collaterals Masaki Tanabe 1 1 Dai-Ni Okamoto General Hospital, Japan [CLINICAL INFORMATION] Patient initials or identifier number. SF Relevant clinical history and physical exam. An 84 y.o. male patient was suffering from worseningdyspnea on effort. He had a chronic total oc- clusion (CTO) at the proximal rightcoronary with rich bridge collaterals. He had been undertaken coronary intervention to the proximal RCA-CTO two times in 2009 and 2012 in our cardiac catheterization laboratory, but without success. Relevant test results prior to catheterization. Prior CTO-PCIs to proximal RCA were performed in 2009 and 2012, however, without success. Various procedural steps had been alreadyattempted at these prior CTO-PCIs; parallel wire techniques, antegrade wiringwith IVUS guid- ance, and retrograde septal wire surfing via transseptally, andre- trograde approach via the epicardial collateral of the atrial branch of theLCX. Relevant catheterization findings. CAG findings showed that RCA was chronically totallyoccluded, which had rich bridge collaterals. The entry of the CTO was uncleardue to these collaterals. The main contralateral collateral was found from theAC branch of the LCX via an AV groove to the RCA PL branch, but it was jailedby the bare metal stent which was implanted in case of emergent PCI due toonset of myocardial infarction over ten years before, and besides had tor- tuousmorphology in the at the middle part. The transseptal collaterals to the PD branchof the RCA were unclear whether there were con- necting to the PD branch of theRCA or not. [INTERVENTIONAL MANAGEMENT] Procedural step. The 3 rd attempted PCI to the proximalRCA-CTO was started by bilateral transfemoral approach after guide catheter- sinsertion using the 7Fr SPB 3.5 with side holes to the LCA and the 7Fr SAL 1.0 with side holes to the RCA. Considering prior failed procedures, retrograde approach was attempted from the beginning. In the tip injection via the 3 rd septal branch using the Car- avelmicrocatheter, it was found that the tiny (however, bending) transseptal collateral was connectedto the PD branch of the RCA. Careful wire manipulation using the Sion blackwith the Caravel sup- port was successfully negotiated and passed throughthistransseptal collateral. After the long Corsair microcatheter advance to the CTO exit, antegradewiringwas started, but it was difficult to penetrate the CTO entry using the UltimateBros.3 with the short Corsair microcatheter, eventually, it managed to be ableto penetrate the CTO entry using the Miracle 12g. Continuously, bilateral wiring within CTO segment was performed using each of the Gaia 2 nd , and then, each wire tip was able to cross- over. Consequently, classic reverse CART technique using 2.5mm balloon and IVUS guided reverse CARTwere performed. Finally, the retrograde Sion black was successfully passedthrough the CTO segment. After wire externalization using the RG3, two BESs were implanted to theproximal RCA-CTO. JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY, VOL. 67, NO. 16, SUPPL S, 2016 S159