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

Is Epicardial Collateral Dilation as Out-of-Bounds Terrain during a Retrograde CTO Approach? 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A Case Report Genrui Chen, Xiaolin Lei, Shuai Zhao, Peng Han, Haokao Gao, Chengxiang Li This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8468744/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract 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. Chronic total occlusions (CTO) Percutaneous coronary intervention (PCI) Epicardial Collaterals (ECs) Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction The use of retrograde crossings in chronic total occlusion (CTO) percutaneous coronary intervention (PCI) provides higher technical success rates 1 – 2 . However, the retrograde approach through epicardial collaterals (ECs) for CTO-PCI is a more challenging procedure than the septal collateral approach. Because of the quite heterogeneous tortuosity and friability 3 – 4 , ECs are associated with difficulties in wiring and microcatheter tracking, especially when balloon dilation is attempted, which carries a high risk of vascular rupture 5 . However, facing the dilemma that the retrograde MCs cannot cross the EC, which is the only option for interventional vessels, meticulous and controlled dilation with a small balloon in the EC to reform the extravascular architecture may facilitate MC crossing. Herein, we present a case of in-stent re-occlusion, in which the only interventional EC vessel was pre-dilated with a small balloon at low pressure because the retrograde MCs were uncrossable, and retrograde CTO recanalization was finally achieved. Case presentation A 69-year-old female first experienced typical exertional angina and chest tightness 18 years ago, and the symptoms recurred one month ago. The patient had a history of type 2 diabetes for eight years. In 2010, stents were successfully implanted in the proximal segments of the LAD for 75% stenosis and a CTO in the LCX, respectively. Three years ago, coronary angiography (CAG) showed in-stent occlusion in the LAD and LCX, as well as 60–80% stenosis at the ostium of the ramus intermediate branch. Subsequently, one DES was implanted from the left main artery (LM) to the ramus branch without treating the in-stent occlusion, and the symptoms were relieved. Recently, symptoms of chest discomfort have worsened, and exercise tolerance has decreased despite receiving optimized medical therapy. Upon admission, pro-B type natriuretic peptide (Pro-BNP) was 1395 pg/mL, and other laboratory tests were within normal limits. The electrocardiogram (ECG) showed sinus rhythm with ST-segment depression and T-wave inversion. Echocardiography demonstrated hypokinesis of the left ventricular anterior wall and reduced left ventricular systolic function, with an LVEF of 40%. The SPECT revealed stress and rest gated myocardial perfusion imaging with severe ischemia in the apical area, the anterior and the lateral walls (approximately 40% of the total left ventricular area). CAG showed with severe restenosis in LM-ramus branch (Fig. 1 A), the LCX was filled by posterior descending (PD) vessel of the coronary artery (RCA) through epicardial collaterals (ECs) (Fig. 1 B). After the in-stent severe restenosis in the LM-ramus branch was dilated, the LM-LCX CTO lesion was primarily attempted via the antegrade approach. IVUS failed to observe LCX ostium due to shielding by the stent struts. Subsequently, the retrograde approach was attempted, and tip injection via the Corsair MC confirmed the feasibility of the ECs from PD to LCX, although it was more tortuous (Fig. 2 A-B). The SUOH03 guidewire crossed the EC into the distal LCX CTO, but the 2.6F Corsair microcatheter (MC) and 1.8F Finecross MC failed to cross the tortuous segment of the EC (Fig. 2 C). Subsequently, the EC was pre-dilated with a 0.8×10 mm balloon at nominal pressure (6 atm) near the resistant point (Fig. 2 D, Video 1) without injuring the EC. A 1.25×10 mm balloon was then used to confirm the passability of the EC. Fortunately, the 1.7F Instantpass MC passed the EC (Fig. 3 A), and tip injection visualized the distal segment of the LCX for retrograde wire penetration (Fig. 3 B). The Gaia 3 guidewire was advanced through the CTO segment until it reached the antegrade guiding catheter. Tip-in technique was performed for Gaia3 wire insertion into the antegrade MC because the limited length of the retrograde MC was unable to reach the antegrade GC (Fig. 3 C). The antegrade MC advanced into the LCX distal lumen (Fig. 3 D), the routine procedure was performed with one DES in the proximal LCX and drug-coated ballons (DCBs) in distal segment, achieving excellent final blood flow (Fig. 3 E-F). No procedural complications occurred. The total fluoroscopy time for the procedure was 148 min, and the total contrast volume used was 350 ml. The patient was followed up for six months and exhibited mild symptoms. Discussion To the best of our knowledge, this is the first report using small balloon dilation to modify epicardial collateral geometry to facilitate MC crossing. The epicardial collateral is a commonly used channel in the retrograde approach. Its advantage is that it facilitates access to the donor branches and the distal vessels of the CTO lesion. The disadvantages are that most vessels are tortuous, spiral-shaped, and have a relatively long course. Additionally, such collaterals have almost no elasticity, and gentle manipulation is required to avoid forceful device advancement; otherwise, pericardial tamponade is likely to occur. CTO guidelines and expert consensus have stipulated that balloon dilation is prohibited for epicardial collaterals to avoid vascular rupture 5 . In this case, the antegrade attempt of the LM-LCX CTO failed, and there was only an epicardial retrograde channel from the PD to the LCX. However, due to tortuosity, neither the Corsair nor the Finecross MC could be advanced through this epicardial channel. At the resistant point, the diameter of the EC was approximately 1 mm, and there was a deep and sharp angle, making it difficult for the MCs to pass through. Therefore, we performed sequential pre-dilation of the resistant segment using a 0.8×10 mm balloon at low pressure. The intrinsic mechanism of small balloon dilation was that the extravascular tissue anatomy was reformed, which subsequently led to alterations in the geometric shape of the EC, thereby slowing down the angle and improving the microcatheter's ability to cross (Fig. 4 ). To minimize the occurrence of perforation, operators must have a clear understanding of the anatomy of ECs and keep in mind the most important principle for dilation: that the ratio between the small balloon and the EC diameter should be approximately 0.8:1, and that no more than the nominal pressure should be used to dilate the EC. Despite its benefits, this technique still faces significant limitations in clinical application, as it requires extensive CTO experience and a thorough understanding of collateral anatomy. These challenges underscore the urgent need for more large-sample studies to establish robust evidence of safety and efficacy, as the current data remain limited. Conclusion This case demonstrates the feasibility of low-pressure small balloon dilation to improve the device delivery through epicardial collaterals, offering important individualized insights for managing similar lesions and accumulating practical evidence for the standardized use of epicardial collaterals in retrograde CTO PCI. Declarations Ethics statement This study was approved by the ethics committee of the Department of Cardiology, the First Affiliated Hospital of Air Force Military Medical University, Xi’an 710032, China. Consent to publish Written informed consent was obtained from the patient for publication of this case report. Competing interests The authors declare no competing interests. Funding This study was supported by the Shaanxi Province Key Research and Development Project (No: 2024GX -YBXM-136). Author Contribution CGL、LXL wrote the main manuscript text ; and HP、ZS、GHK prepared figures 1-4. LCX supervise the paper. the All authors reviewed the manuscript. Data availability No datasets were generated or analysed during the current study. References Chan CY, Wu EB, Yan BP, Tsuchikane E. Procedure failure of chronic total occlusion percutaneous coronary intervention in an algorithm driven contemporary Asia-Pacific Chronic Total Occlusion Club (APCTO Club) multicenter registry. Catheter Cardiovasc Interv. 2019;93:1033–8. Maeremans J, Walsh S, Knaapen P, Spratt JC, Avran A, Hanratty CG, Faurie B, Agostoni P, Bressollette E, Kayaert P, et al. The Hybrid Algorithm for Treating Chronic Total Occlusions in Europe: The RECHARGE Registry. J Am Coll Cardiol. 2016;68:1958–70. Tajti P, Karmpaliotis D, Alaswad K, Jaffer FA, Yeh RW, Patel M, Mahmud E, Choi JW, Burke MN, Doing AH, et al. The Hybrid Approach to Chronic Total Occlusion Percutaneous Coronary Intervention: Update From the PROGRESS CTO Registry. JACC Cardiovasc Interv. 2018;11:1325–35. Tanaka H, Tsuchikane E, Muramatsu T, Kishi K, Muto M, Oikawa Y, Kawasaki T, Hamazaki Y, Fujita T, Katoh O. A Novel Algorithm for Treating Chronic Total Coronary Artery Occlusion. J Am Coll Cardiol. 2019;74:2392–404. Wu EB, Tsuchikane E, Lo S, Lim ST, Ge L, Chen JY, Qian J, Lee SW, Harding S, Kao HL. Retrograde algorithm for chronic total occlusion from the Asia Pacific Chronic Total Occlusion club. AsiaIntervention. 2018;4:98–107. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 19 Jan, 2026 Reviews received at journal 16 Jan, 2026 Reviews received at journal 14 Jan, 2026 Reviewers agreed at journal 14 Jan, 2026 Reviewers agreed at journal 12 Jan, 2026 Reviewers invited by journal 12 Jan, 2026 Editor invited by journal 12 Jan, 2026 Editor assigned by journal 09 Jan, 2026 Submission checks completed at journal 09 Jan, 2026 First submitted to journal 28 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8468744","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":573559672,"identity":"dba303e1-fef3-446d-bf26-d30b16385925","order_by":0,"name":"Genrui Chen","email":"","orcid":"","institution":"First Affiliated Hospital of Xi’an Jiaotong University","correspondingAuthor":false,"prefix":"","firstName":"Genrui","middleName":"","lastName":"Chen","suffix":""},{"id":573559675,"identity":"98909e56-e137-42c6-9df8-e6ae95081186","order_by":1,"name":"Xiaolin Lei","email":"","orcid":"","institution":"Department of Cardiology, Xijing Hospital, The 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12:00:16","extension":"xml","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":26326,"visible":true,"origin":"","legend":"","description":"","filename":"01af799e6090455cab3425ae10dc46b91structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8468744/v1/79938b8d0d4cc3c5be370ffc.xml"},{"id":100401965,"identity":"2824bd2b-5035-4e9b-b5d7-3718fad729b9","added_by":"auto","created_at":"2026-01-16 11:59:31","extension":"html","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":31016,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8468744/v1/51c169d80b2e85bc070fbeaf.html"},{"id":100402403,"identity":"56afe57f-bee8-4430-803b-4960f6e61030","added_by":"auto","created_at":"2026-01-16 12:00:05","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":200420,"visible":true,"origin":"","legend":"\u003cp\u003eLeft coronary artery angiography. A: Left main to ramup severe restenosis; (B): Right coronary artery with mild stenosis.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8468744/v1/26d29eafc0349624130e84d9.jpeg"},{"id":100402181,"identity":"c5710cd6-619a-483d-9d19-e5af2e1f98b3","added_by":"auto","created_at":"2026-01-16 11:59:47","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":264506,"visible":true,"origin":"","legend":"\u003cp\u003eEpicardial collateral dilation with small balloon. A-B: the tortuous EC. C: MC uncross at this segment (yellow dotted circle), which was indicated in B with red dotted circle. D: small balloon dilated the resistant point (blue yellow dotted circle).\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8468744/v1/29b4610917f8c05e4ca7f6b7.jpeg"},{"id":100402486,"identity":"084f71f5-33e7-4c9d-acce-df0f860fd193","added_by":"auto","created_at":"2026-01-16 12:00:15","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":291607,"visible":true,"origin":"","legend":"\u003cp\u003eLCX CTO recanalization. A: MC crossed EC. B: Tip-injection for distal LCX visualization. C: Tip-in technique for antegrade conversion. D: antegrade MC crossed along the retrograde wire. E-F: LCX with good flow.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8468744/v1/087778517b6f9b61ce70d14b.jpeg"},{"id":100400424,"identity":"60df9668-99c3-4547-850e-c49b0ada9098","added_by":"auto","created_at":"2026-01-16 11:58:08","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":228737,"visible":true,"origin":"","legend":"\u003cp\u003eThe mechanism depiction for EC geometry modified by small balloon dilation.\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8468744/v1/a9397ca43377906e4edd244e.jpeg"},{"id":100422859,"identity":"b1b176f6-f6f8-4b23-bc17-956c4d21f7a3","added_by":"auto","created_at":"2026-01-16 14:11:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1288105,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8468744/v1/4c08c313-887b-4cc6-ae2b-f694167a9944.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Is Epicardial Collateral Dilation as Out-of-Bounds Terrain during a Retrograde CTO Approach? A Case Report","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe use of retrograde crossings in chronic total occlusion (CTO) percutaneous coronary intervention (PCI) provides higher technical success rates\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. However, the retrograde approach through epicardial collaterals (ECs) for CTO-PCI is a more challenging procedure than the septal collateral approach. Because of the quite heterogeneous tortuosity and friability\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e, ECs are associated with difficulties in wiring and microcatheter tracking, especially when balloon dilation is attempted, which carries a high risk of vascular rupture\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. However, facing the dilemma that the retrograde MCs cannot cross the EC, which is the only option for interventional vessels, meticulous and controlled dilation with a small balloon in the EC to reform the extravascular architecture may facilitate MC crossing. Herein, we present a case of in-stent re-occlusion, in which the only interventional EC vessel was pre-dilated with a small balloon at low pressure because the retrograde MCs were uncrossable, and retrograde CTO recanalization was finally achieved.\u003c/p\u003e"},{"header":"Case presentation","content":"\u003cp\u003eA 69-year-old female first experienced typical exertional angina and chest tightness 18 years ago, and the symptoms recurred one month ago. The patient had a history of type 2 diabetes for eight years. In 2010, stents were successfully implanted in the proximal segments of the LAD for 75% stenosis and a CTO in the LCX, respectively. Three years ago, coronary angiography (CAG) showed in-stent occlusion in the LAD and LCX, as well as 60\u0026ndash;80% stenosis at the ostium of the ramus intermediate branch. Subsequently, one DES was implanted from the left main artery (LM) to the ramus branch without treating the in-stent occlusion, and the symptoms were relieved. Recently, symptoms of chest discomfort have worsened, and exercise tolerance has decreased despite receiving optimized medical therapy. Upon admission, pro-B type natriuretic peptide (Pro-BNP) was 1395 pg/mL, and other laboratory tests were within normal limits. The electrocardiogram (ECG) showed sinus rhythm with ST-segment depression and T-wave inversion. Echocardiography demonstrated hypokinesis of the left ventricular anterior wall and reduced left ventricular systolic function, with an LVEF of 40%. The SPECT revealed stress and rest gated myocardial perfusion imaging with severe ischemia in the apical area, the anterior and the lateral walls (approximately 40% of the total left ventricular area).\u003c/p\u003e \u003cp\u003eCAG showed with severe restenosis in LM-ramus branch (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA), the LCX was filled by posterior descending (PD) vessel of the coronary artery (RCA) through epicardial collaterals (ECs) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB). After the in-stent severe restenosis in the LM-ramus branch was dilated, the LM-LCX CTO lesion was primarily attempted via the antegrade approach.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIVUS failed to observe LCX ostium due to shielding by the stent struts. Subsequently, the retrograde approach was attempted, and tip injection via the Corsair MC confirmed the feasibility of the ECs from PD to LCX, although it was more tortuous (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA-B). The SUOH03 guidewire crossed the EC into the distal LCX CTO, but the 2.6F Corsair microcatheter (MC) and 1.8F Finecross MC failed to cross the tortuous segment of the EC (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSubsequently, the EC was pre-dilated with a 0.8\u0026times;10 mm balloon at nominal pressure (6 atm) near the resistant point (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD, Video 1) without injuring the EC. A 1.25\u0026times;10 mm balloon was then used to confirm the passability of the EC. Fortunately, the 1.7F Instantpass MC passed the EC (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA), and tip injection visualized the distal segment of the LCX for retrograde wire penetration (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB). The Gaia 3 guidewire was advanced through the CTO segment until it reached the antegrade guiding catheter. Tip-in technique was performed for Gaia3 wire insertion into the antegrade MC because the limited length of the retrograde MC was unable to reach the antegrade GC (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC). The antegrade MC advanced into the LCX distal lumen (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD), the routine procedure was performed with one DES in the proximal LCX and drug-coated ballons (DCBs) in distal segment, achieving excellent final blood flow (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eE-F). No procedural complications occurred. The total fluoroscopy time for the procedure was 148 min, and the total contrast volume used was 350 ml. The patient was followed up for six months and exhibited mild symptoms.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eTo the best of our knowledge, this is the first report using small balloon dilation to modify epicardial collateral geometry to facilitate MC crossing.\u003c/p\u003e \u003cp\u003eThe epicardial collateral is a commonly used channel in the retrograde approach. Its advantage is that it facilitates access to the donor branches and the distal vessels of the CTO lesion. The disadvantages are that most vessels are tortuous, spiral-shaped, and have a relatively long course. Additionally, such collaterals have almost no elasticity, and gentle manipulation is required to avoid forceful device advancement; otherwise, pericardial tamponade is likely to occur. CTO guidelines and expert consensus have stipulated that balloon dilation is prohibited for epicardial collaterals to avoid vascular rupture\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn this case, the antegrade attempt of the LM-LCX CTO failed, and there was only an epicardial retrograde channel from the PD to the LCX. However, due to tortuosity, neither the Corsair nor the Finecross MC could be advanced through this epicardial channel. At the resistant point, the diameter of the EC was approximately 1 mm, and there was a deep and sharp angle, making it difficult for the MCs to pass through. Therefore, we performed sequential pre-dilation of the resistant segment using a 0.8\u0026times;10 mm balloon at low pressure. The intrinsic mechanism of small balloon dilation was that the extravascular tissue anatomy was reformed, which subsequently led to alterations in the geometric shape of the EC, thereby slowing down the angle and improving the microcatheter's ability to cross (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). To minimize the occurrence of perforation, operators must have a clear understanding of the anatomy of ECs and keep in mind the most important principle for dilation: that the ratio between the small balloon and the EC diameter should be approximately 0.8:1, and that no more than the nominal pressure should be used to dilate the EC. Despite its benefits, this technique still faces significant limitations in clinical application, as it requires extensive CTO experience and a thorough understanding of collateral anatomy. These challenges underscore the urgent need for more large-sample studies to establish robust evidence of safety and efficacy, as the current data remain limited.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis case demonstrates the feasibility of low-pressure small balloon dilation to improve the device delivery through epicardial collaterals, offering important individualized insights for managing similar lesions and accumulating practical evidence for the standardized use of epicardial collaterals in retrograde CTO PCI.\u003c/p\u003e"},{"header":"Declarations","content":" \u003cp\u003e \u003cb\u003eEthics statement\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThis study was approved by the ethics committee of the Department of Cardiology, the First Affiliated Hospital of Air Force Military Medical University, Xi\u0026rsquo;an 710032, China.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent to publish\u003c/strong\u003e \u003cp\u003eWritten informed consent was obtained from the patient for publication of this case report.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eCompeting interests\u003c/strong\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis study was supported by the Shaanxi Province Key Research and Development Project (No: 2024GX -YBXM-136).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eCGL、LXL wrote the main manuscript text ; and HP、ZS、GHK prepared figures 1-4. LCX supervise the paper. the All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eNo datasets were generated or analysed during the current study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChan CY, Wu EB, Yan BP, Tsuchikane E. Procedure failure of chronic total occlusion percutaneous coronary intervention in an algorithm driven contemporary Asia-Pacific Chronic Total Occlusion Club (APCTO Club) multicenter registry. Catheter Cardiovasc Interv. 2019;93:1033\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMaeremans J, Walsh S, Knaapen P, Spratt JC, Avran A, Hanratty CG, Faurie B, Agostoni P, Bressollette E, Kayaert P, et al. The Hybrid Algorithm for Treating Chronic Total Occlusions in Europe: The RECHARGE Registry. J Am Coll Cardiol. 2016;68:1958\u0026ndash;70.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTajti P, Karmpaliotis D, Alaswad K, Jaffer FA, Yeh RW, Patel M, Mahmud E, Choi JW, Burke MN, Doing AH, et al. The Hybrid Approach to Chronic Total Occlusion Percutaneous Coronary Intervention: Update From the PROGRESS CTO Registry. JACC Cardiovasc Interv. 2018;11:1325\u0026ndash;35.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTanaka H, Tsuchikane E, Muramatsu T, Kishi K, Muto M, Oikawa Y, Kawasaki T, Hamazaki Y, Fujita T, Katoh O. A Novel Algorithm for Treating Chronic Total Coronary Artery Occlusion. J Am Coll Cardiol. 2019;74:2392\u0026ndash;404.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu EB, Tsuchikane E, Lo S, Lim ST, Ge L, Chen JY, Qian J, Lee SW, Harding S, Kao HL. Retrograde algorithm for chronic total occlusion from the Asia Pacific Chronic Total Occlusion club. AsiaIntervention. 2018;4:98\u0026ndash;107.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-cardiovascular-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bcar","sideBox":"Learn more about [BMC Cardiovascular Disorders](http://bmccardiovascdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bcar/default.aspx","title":"BMC Cardiovascular Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Chronic total occlusions (CTO), Percutaneous coronary intervention (PCI), Epicardial Collaterals (ECs)","lastPublishedDoi":"10.21203/rs.3.rs-8468744/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8468744/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe 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\u0026times;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.\u003c/p\u003e","manuscriptTitle":"Is Epicardial Collateral Dilation as Out-of-Bounds Terrain during a Retrograde CTO Approach? A Case Report","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-16 09:16:49","doi":"10.21203/rs.3.rs-8468744/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-19T06:26:11+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-16T11:29:20+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-15T00:14:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"65508183161067766664346079809512514512","date":"2026-01-14T23:50:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"309364713601382638907320466735726328136","date":"2026-01-13T00:05:21+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-12T16:16:14+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-01-12T09:37:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-09T11:29:38+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-09T11:24:47+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Cardiovascular Disorders","date":"2025-12-29T03:12:57+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-cardiovascular-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bcar","sideBox":"Learn more about [BMC Cardiovascular Disorders](http://bmccardiovascdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bcar/default.aspx","title":"BMC Cardiovascular Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e8debfe6-5ec9-4e9c-addb-9436efd331ee","owner":[],"postedDate":"January 16th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-13T08:39:05+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-16 09:16:49","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8468744","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8468744","identity":"rs-8468744","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}