Isolated Aneurysmal Major Aortopulmonary Collateral Artery in a Structurally Normal Adult: Computed Tomography Angiography Diagnosis and Endovascular Exclusion

Isolated Aneurysmal Major Aortopulmonary Collateral Artery in a Structurally Normal Adult: Computed Tomography Angiography Diagnosis and Endovascular Exclusion | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Case Report Isolated Aneurysmal Major Aortopulmonary Collateral Artery in a Structurally Normal Adult: Computed Tomography Angiography Diagnosis and Endovascular Exclusion Saubhagya Dhakal, Nikahat Yasmine, Nevzat Karabulut This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9164305/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 12 You are reading this latest preprint version Abstract Background: Major aortopulmonary collateral arteries (MAPCAs) are anomalous systemic-to-pulmonary vessels typically associated with complex congenital heart disease. Isolated MAPCAs in adults without structural cardiac abnormalities are exceedingly rare, and aneurysmal degeneration is even more uncommon. Case presentation: We report a 48-year-old man presenting with acute non-exertional chest pain. Computed tomography angiography (CTA) demonstrated a 2.6-cm saccular aneurysm arising from an isolated MAPCA originating from the proximal descending thoracic aorta and supplying the left lower lobe pulmonary artery. CTA delineated the vascular anatomy and excluded associated congenital cardiac abnormalities. Digital subtraction angiography confirmed a single systemic-to-pulmonary arterial communication. The patient underwent thoracic endovascular aortic repair with adjunctive coil embolization, resulting in complete aneurysm exclusion and symptom resolution. Conclusions: This case highlights the importance of recognizing isolated aneurysmal MAPCAs in adults, the value of CTA in diagnosis and procedural planning, and the effectiveness of endovascular therapy in preventing potentially life-threatening complications. major aortopulmonary collateral artery MAPCA aneurysm computed tomography angiography thoracic endovascular aortic repair coil embolization chest pain Figures Figure 1 Figure 2 Figure 3 1. Introduction Major aortopulmonary collateral arteries (MAPCAs) are abnormal systemic arteries that provide pulmonary blood flow in patients with congenital heart disease, particularly pulmonary atresia and tetralogy of Fallot [ 1 – 3 ]. These vessels arise from persistent embryologic systemic-to-pulmonary arterial connections that normally regress during development of the sixth aortic arch and native pulmonary arteries [ 4 ]. MAPCAs are well recognized in neonates and infants with complex congenital heart disease; however, isolated MAPCAs in adults with a structurally normal heart are extremely uncommon and have been described only rarely in the literature [ 1 , 2 ]. Aneurysmal transformation of a MAPCA is particularly unusual but clinically important because of the risk of rupture, hemoptysis, mediastinal hemorrhage, or other acute complications [ 5 – 8 ]. In adults without congenital heart disease, such lesions may pose a diagnostic challenge because they are unexpected and may mimic other mediastinal or aortic abnormalities. Early recognition is therefore essential to guide timely management. We report a rare case of an isolated aneurysmal MAPCA in a structurally normal adult presenting with acute chest pain, diagnosed with computed tomography angiography (CTA) and successfully treated with thoracic endovascular aortic repair (TEVAR) and adjunctive coil embolization. 2. Case presentation A 48-year-old man with no prior cardiovascular or pulmonary history presented with acute non-exertional chest pain. He denied dyspnea, hemoptysis, syncope, palpitations, or fever. There was no known history of congenital heart disease. Electrocardiography demonstrated normal sinus rhythm without ischemic changes. Cardiac biomarkers and D-dimer levels were within normal limits. Transthoracic echocardiography revealed a large aneurysmal vascular structure adjacent to the proximal descending thoracic aorta. Contrast-enhanced CTA of the chest was subsequently performed to exclude pulmonary embolism or acute aortic pathology. CTA demonstrated a markedly dilated and tortuous systemic vessel arising from the proximal descending thoracic aorta, consistent with an enlarged major aortopulmonary collateral artery. A focal proximal saccular aneurysm measuring 2.6 cm was identified (Figs. 1 and 2 ). The vessel coursed inferiorly and supplied the left lower lobe pulmonary artery, establishing a systemic-to-pulmonary arterial connection. No pulmonary atresia, ventricular septal defect, patent ductus arteriosus, or other structural cardiac abnormality was identified. Digital subtraction angiography confirmed a single systemic-to-pulmonary arterial communication consistent with an isolated aneurysmal MAPCA (Fig. 2 ). Given the aneurysmal morphology and potential risk of rupture, a multidisciplinary decision was made to proceed with endovascular exclusion. The patient underwent TEVAR with adjunctive coil embolization of the collateral vessel. Post-procedural imaging demonstrated complete exclusion of the aneurysm without residual shunt (Fig. 3 ). The patient experienced complete symptom resolution after the procedure and remained asymptomatic at 3-month follow-up. 3. Discussion MAPCAs are most frequently encountered in pediatric patients with congenital heart disease and diminished pulmonary blood flow [ 1 – 3 ]. Their embryologic basis involves persistence of primitive systemic-to-pulmonary arterial connections that fail to regress during normal development [ 4 ]. In contrast, isolated MAPCAs in adults without associated congenital cardiac abnormalities are exceedingly rare. Aneurysmal degeneration in this setting is even more unusual and has only rarely been described [ 5 – 8 ]. In the present case, the absence of structural congenital heart disease makes this vascular anomaly particularly uncommon. Previously reported MAPCA aneurysms have predominantly occurred in association with congenital cardiac abnormalities, pulmonary atresia, or unilateral absence of a pulmonary artery [ 5 – 8 ]. The rarity of aneurysmal degeneration in an isolated MAPCA underscores the importance of recognizing this entity when evaluating unusual thoracic vascular lesions in adults. The mechanism of aneurysm formation in this case is likely related to chronic exposure of a persistent embryologic collateral vessel to systemic arterial pressure. MAPCAs arise from primitive systemic arteries that are normally transient during development [ 4 ]. When such a vessel persists into adulthood, continuous high-pressure flow from the thoracic aorta may result in focal wall stress, particularly near the aortic origin or along tortuous segments, promoting progressive weakening and saccular dilatation [ 6 , 7 ]. Notably, our patient had no imaging evidence of pulmonary arterial enlargement, pulmonary hypertension, or increased pulmonary vascular resistance, suggesting that aneurysm formation was more likely driven by local hemodynamic factors than by generalized pulmonary vascular overload. The patient’s acute chest pain was most plausibly related to aneurysmal wall stress or stretching of adjacent mediastinal structures. Although some MAPCAs may remain asymptomatic, aneurysmal dilation substantially increases the risk of catastrophic events, including rupture and hemorrhage [ 6 – 8 ]. This clinical concern supported definitive treatment even in the absence of frank rupture. CTA played a pivotal role in this case by accurately depicting the origin, course, and aneurysmal morphology of the collateral vessel, as well as its communication with the pulmonary circulation. In addition, CTA excluded associated congenital cardiac abnormalities and provided essential information for procedural planning. Multiplanar and three-dimensional reconstructions are especially helpful in defining the spatial relationship of these anomalous vessels to the thoracic aorta and pulmonary arteries. Digital subtraction angiography remains important for confirming the diagnosis and facilitating endovascular treatment. From a management perspective, endovascular therapy offers a minimally invasive and effective approach for exclusion of MAPCA aneurysms. Techniques including coil embolization, vascular plug placement, and thoracic endovascular stent-graft exclusion have all been described in selected cases [ 6 , 7 ]. In the present case, combined TEVAR and adjunctive coil embolization achieved complete aneurysm exclusion with excellent short-term clinical outcome. Compared with open surgical treatment, endovascular management may reduce procedural morbidity while providing definitive therapy in appropriately selected patients. Recognition of this rare vascular anomaly is important for cardiologists, cardiovascular imagers, and interventional specialists because delayed diagnosis may expose patients to preventable complications. Early identification and prompt treatment can avert rupture and achieve durable symptom relief. 4. Conclusion Isolated aneurysmal MAPCA in an adult without congenital heart disease is an exceptionally rare but potentially life-threatening vascular anomaly. CTA is crucial for accurate diagnosis, exclusion of associated congenital cardiac abnormalities, and endovascular procedural planning. Timely endovascular intervention with TEVAR and coil embolization can provide safe and effective aneurysm exclusion and prevent catastrophic complications. Abbreviations MAPCA Major aortopulmonary collateral artery CTA Computed tomography angiography TEVAR Thoracic endovascular aortic repair CT Computed tomography Declarations Ethical approval Not applicable. Consent to participate Written informed consent was obtained from the patient. Consent for publication The patient provided written consent for publication of anonymized clinical data and images. Funding No funding was received. References Haworth SG. Major aortopulmonary collateral arteries in pulmonary atresia. Circulation . 1980;62:104–110. Goo HW. CT evaluation of major aortopulmonary collateral arteries in congenital heart disease. Radiographics . 2003;23:S181–S197. Lee EY, Boiselle PM, Cleveland RH. Multidetector CT evaluation of thoracic vascular anomalies. AJR Am J Roentgenol . 2008;190:748–760. Rabinovitch M, Herrera-deLeon V, Castaneda AR, Reid LM. Growth and development of pulmonary collateral vessels. Circulation . 1981;64:1230–1240. Kwak JG, Lee CH, Kim SH. Giant aneurysm of a major aortopulmonary collateral artery. J Thorac Cardiovasc Surg . 2014;148:e241–e243. Joynt MR, Lu JC, Bocks ML, Crowley DC. Ruptured aneurysm of a major aortopulmonary collateral. Eur Heart J . 2016;37:1777. Sharma A, Kumar S, Priya S. Ruptured aneurysm of major aortopulmonary collateral artery: management using Amplatzer vascular plug. Cardiovasc Diagn Ther . 2016;6:310–314. Tatsumoto S, Kobayashi K, Mizuno Y, Nagata T. Rupture of a mediastinal collateral aneurysm associated with unilateral absence of pulmonary artery. J Vasc Surg Cases Innov Tech . 2024;11. Additional Declarations No competing interests reported. Supplementary Files CAREchecklistEnglish2013EGYPTHEARTJOURNAL.pdf Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 03 May, 2026 Reviews received at journal 02 May, 2026 Reviews received at journal 01 May, 2026 Reviewers agreed at journal 22 Apr, 2026 Reviewers agreed at journal 21 Apr, 2026 Reviews received at journal 01 Apr, 2026 Reviewers agreed at journal 31 Mar, 2026 Reviewers agreed at journal 26 Mar, 2026 Reviewers invited by journal 26 Mar, 2026 Editor assigned by journal 22 Mar, 2026 Submission checks completed at journal 22 Mar, 2026 First submitted to journal 18 Mar, 2026 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. 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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-9164305","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":612967210,"identity":"ef9dabbb-6a7e-4d31-9e5a-bde0f08b2fcb","order_by":0,"name":"Saubhagya Dhakal","email":"data:image/png;base64,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","orcid":"","institution":"University Of Iowa hospital and clinics","correspondingAuthor":true,"prefix":"","firstName":"Saubhagya","middleName":"","lastName":"Dhakal","suffix":""},{"id":612967211,"identity":"2d42b2ba-60cc-4ff4-a66b-61bbcb1d52d2","order_by":1,"name":"Nikahat Yasmine","email":"","orcid":"","institution":"University Of Iowa hospital and clinics","correspondingAuthor":false,"prefix":"","firstName":"Nikahat","middleName":"","lastName":"Yasmine","suffix":""},{"id":612967212,"identity":"927f12dc-bcfb-4760-abef-e14ebc28c91c","order_by":2,"name":"Nevzat Karabulut","email":"","orcid":"","institution":"University Of Iowa hospital and clinics","correspondingAuthor":false,"prefix":"","firstName":"Nevzat","middleName":"","lastName":"Karabulut","suffix":""}],"badges":[],"createdAt":"2026-03-19 03:09:29","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9164305/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9164305/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105787945,"identity":"cb53c692-bd05-4478-8178-d97322b592a9","added_by":"auto","created_at":"2026-03-31 06:57:47","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":454613,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCTA demonstrating an aneurysmal major aortopulmonary collateral artery (MAPCA).\u003c/strong\u003e\u003cbr\u003e\n(A) Coronal volume-rendered reconstruction shows a tortuous systemic vessel arising from the descending thoracic aorta with focal saccular aneurysmal dilatation (white arrow).\u003cbr\u003e\n(B) Coronal maximum-intensity projection image acquired in the aortic phase demonstrates the aneurysmal MAPCA (blue arrow) extending toward the left lower lobe pulmonary artery (red arrow). Note the absence of contrast in the proximal left pulmonary artery (asterisk).\u003cbr\u003e\n(C) Sagittal maximum-intensity projection image depicts the aneurysmal MAPCA (blue arrow) and its communication with the pulmonary artery (red arrow). Note the absence of contrast in the proximal left pulmonary artery (asterisk).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9164305/v1/dff0aaae71e97a4778fc87c1.png"},{"id":105787974,"identity":"b1ae48e0-a233-4fc0-8590-75efaca5c9aa","added_by":"auto","created_at":"2026-03-31 06:57:53","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":575483,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDigital subtraction angiography confirming systemic-to-pulmonary arterial communication.\u003c/strong\u003e\u003cbr\u003e\n(A) Angiographic image demonstrates the aneurysmal MAPCA.\u003cbr\u003e\n(B) Angiographic image shows extension of the MAPCA toward the descending pulmonary artery.\u003cbr\u003e\n(C) Pulmonary angiogram shows normal opacification of the pulmonary arterial vasculature without direct visualization of the MAPCA.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9164305/v1/70e789e742e2855765460533.png"},{"id":105787924,"identity":"d1f5a8aa-9001-4cbe-bedb-d1104c5011a7","added_by":"auto","created_at":"2026-03-31 06:57:42","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":340648,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePost-intervention imaging demonstrating successful aneurysm exclusion following thoracic endovascular aortic repair (TEVAR) with adjunctive coil embolization.\u003c/strong\u003e\u003cbr\u003e\n(A) Coronal multiplanar reconstruction CT image shows the endovascular stent graft within the thoracic aorta (white arrow) and embolization coils within the MAPCA (blue arrow).\u003cbr\u003e\n(B) Chest radiograph demonstrates the thoracic endovascular stent graft and embolization coils.\u003cbr\u003e\n(C) Follow-up angiographic volume-rendered image shows absence of contrast opacification of the previously aneurysmal MAPCA, consistent with successful treatment\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9164305/v1/c16a72424b361fd58274eeca.png"},{"id":105788041,"identity":"5d845f3e-dc90-4c88-8238-4c1a5dff0c9e","added_by":"auto","created_at":"2026-03-31 06:58:03","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2097754,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9164305/v1/7c9b0d38-2c40-4b1f-bb99-4dd09b0aa86c.pdf"},{"id":105787925,"identity":"1ca63082-d720-4bb1-b44a-1e17fabe5db6","added_by":"auto","created_at":"2026-03-31 06:57:42","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":725310,"visible":true,"origin":"","legend":"","description":"","filename":"CAREchecklistEnglish2013EGYPTHEARTJOURNAL.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9164305/v1/d1adb127ed08e8f294f5754b.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Isolated Aneurysmal Major Aortopulmonary Collateral Artery in a Structurally Normal Adult: Computed Tomography Angiography Diagnosis and Endovascular Exclusion","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eMajor aortopulmonary collateral arteries (MAPCAs) are abnormal systemic arteries that provide pulmonary blood flow in patients with congenital heart disease, particularly pulmonary atresia and tetralogy of Fallot [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. These vessels arise from persistent embryologic systemic-to-pulmonary arterial connections that normally regress during development of the sixth aortic arch and native pulmonary arteries [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. MAPCAs are well recognized in neonates and infants with complex congenital heart disease; however, isolated MAPCAs in adults with a structurally normal heart are extremely uncommon and have been described only rarely in the literature [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAneurysmal transformation of a MAPCA is particularly unusual but clinically important because of the risk of rupture, hemoptysis, mediastinal hemorrhage, or other acute complications [\u003cspan additionalcitationids=\"CR6 CR7\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. In adults without congenital heart disease, such lesions may pose a diagnostic challenge because they are unexpected and may mimic other mediastinal or aortic abnormalities. Early recognition is therefore essential to guide timely management.\u003c/p\u003e \u003cp\u003eWe report a rare case of an isolated aneurysmal MAPCA in a structurally normal adult presenting with acute chest pain, diagnosed with computed tomography angiography (CTA) and successfully treated with thoracic endovascular aortic repair (TEVAR) and adjunctive coil embolization.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"2. Case presentation","content":"\u003cp\u003eA 48-year-old man with no prior cardiovascular or pulmonary history presented with acute non-exertional chest pain. He denied dyspnea, hemoptysis, syncope, palpitations, or fever. There was no known history of congenital heart disease. Electrocardiography demonstrated normal sinus rhythm without ischemic changes. Cardiac biomarkers and D-dimer levels were within normal limits. Transthoracic echocardiography revealed a large aneurysmal vascular structure adjacent to the proximal descending thoracic aorta. Contrast-enhanced CTA of the chest was subsequently performed to exclude pulmonary embolism or acute aortic pathology.\u003c/p\u003e \u003cp\u003eCTA demonstrated a markedly dilated and tortuous systemic vessel arising from the proximal descending thoracic aorta, consistent with an enlarged major aortopulmonary collateral artery. A focal proximal saccular aneurysm measuring 2.6 cm was identified (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The vessel coursed inferiorly and supplied the left lower lobe pulmonary artery, establishing a systemic-to-pulmonary arterial connection. No pulmonary atresia, ventricular septal defect, patent ductus arteriosus, or other structural cardiac abnormality was identified.\u003c/p\u003e \u003cp\u003eDigital subtraction angiography confirmed a single systemic-to-pulmonary arterial communication consistent with an isolated aneurysmal MAPCA (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Given the aneurysmal morphology and potential risk of rupture, a multidisciplinary decision was made to proceed with endovascular exclusion. The patient underwent TEVAR with adjunctive coil embolization of the collateral vessel. Post-procedural imaging demonstrated complete exclusion of the aneurysm without residual shunt (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The patient experienced complete symptom resolution after the procedure and remained asymptomatic at 3-month follow-up.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"3. Discussion","content":"\u003cp\u003eMAPCAs are most frequently encountered in pediatric patients with congenital heart disease and diminished pulmonary blood flow [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Their embryologic basis involves persistence of primitive systemic-to-pulmonary arterial connections that fail to regress during normal development [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. In contrast, isolated MAPCAs in adults without associated congenital cardiac abnormalities are exceedingly rare. Aneurysmal degeneration in this setting is even more unusual and has only rarely been described [\u003cspan additionalcitationids=\"CR6 CR7\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the present case, the absence of structural congenital heart disease makes this vascular anomaly particularly uncommon. Previously reported MAPCA aneurysms have predominantly occurred in association with congenital cardiac abnormalities, pulmonary atresia, or unilateral absence of a pulmonary artery [\u003cspan additionalcitationids=\"CR6 CR7\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The rarity of aneurysmal degeneration in an isolated MAPCA underscores the importance of recognizing this entity when evaluating unusual thoracic vascular lesions in adults.\u003c/p\u003e \u003cp\u003eThe mechanism of aneurysm formation in this case is likely related to chronic exposure of a persistent embryologic collateral vessel to systemic arterial pressure. MAPCAs arise from primitive systemic arteries that are normally transient during development [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. When such a vessel persists into adulthood, continuous high-pressure flow from the thoracic aorta may result in focal wall stress, particularly near the aortic origin or along tortuous segments, promoting progressive weakening and saccular dilatation [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Notably, our patient had no imaging evidence of pulmonary arterial enlargement, pulmonary hypertension, or increased pulmonary vascular resistance, suggesting that aneurysm formation was more likely driven by local hemodynamic factors than by generalized pulmonary vascular overload.\u003c/p\u003e \u003cp\u003eThe patient\u0026rsquo;s acute chest pain was most plausibly related to aneurysmal wall stress or stretching of adjacent mediastinal structures. Although some MAPCAs may remain asymptomatic, aneurysmal dilation substantially increases the risk of catastrophic events, including rupture and hemorrhage [\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. This clinical concern supported definitive treatment even in the absence of frank rupture.\u003c/p\u003e \u003cp\u003eCTA played a pivotal role in this case by accurately depicting the origin, course, and aneurysmal morphology of the collateral vessel, as well as its communication with the pulmonary circulation. In addition, CTA excluded associated congenital cardiac abnormalities and provided essential information for procedural planning. Multiplanar and three-dimensional reconstructions are especially helpful in defining the spatial relationship of these anomalous vessels to the thoracic aorta and pulmonary arteries. Digital subtraction angiography remains important for confirming the diagnosis and facilitating endovascular treatment.\u003c/p\u003e \u003cp\u003eFrom a management perspective, endovascular therapy offers a minimally invasive and effective approach for exclusion of MAPCA aneurysms. Techniques including coil embolization, vascular plug placement, and thoracic endovascular stent-graft exclusion have all been described in selected cases [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. In the present case, combined TEVAR and adjunctive coil embolization achieved complete aneurysm exclusion with excellent short-term clinical outcome. Compared with open surgical treatment, endovascular management may reduce procedural morbidity while providing definitive therapy in appropriately selected patients.\u003c/p\u003e \u003cp\u003eRecognition of this rare vascular anomaly is important for cardiologists, cardiovascular imagers, and interventional specialists because delayed diagnosis may expose patients to preventable complications. Early identification and prompt treatment can avert rupture and achieve durable symptom relief.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIsolated aneurysmal MAPCA in an adult without congenital heart disease is an exceptionally rare but potentially life-threatening vascular anomaly. CTA is crucial for accurate diagnosis, exclusion of associated congenital cardiac abnormalities, and endovascular procedural planning. Timely endovascular intervention with TEVAR and coil embolization can provide safe and effective aneurysm exclusion and prevent catastrophic complications.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMAPCA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMajor aortopulmonary collateral artery\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCTA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eComputed tomography angiography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eTEVAR\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eThoracic endovascular aortic repair\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCT\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eComputed tomography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Written informed consent was obtained from the patient.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The patient provided written consent for publication of anonymized clinical data and images.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;No funding was received.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eHaworth SG. Major aortopulmonary collateral arteries in pulmonary atresia. \u003cem\u003eCirculation\u003c/em\u003e. 1980;62:104\u0026ndash;110.\u003c/li\u003e\n \u003cli\u003eGoo HW. CT evaluation of major aortopulmonary collateral arteries in congenital heart disease. \u003cem\u003eRadiographics\u003c/em\u003e. 2003;23:S181\u0026ndash;S197.\u003c/li\u003e\n \u003cli\u003eLee EY, Boiselle PM, Cleveland RH. Multidetector CT evaluation of thoracic vascular anomalies. \u003cem\u003eAJR Am J Roentgenol\u003c/em\u003e. 2008;190:748\u0026ndash;760.\u003c/li\u003e\n \u003cli\u003eRabinovitch M, Herrera-deLeon V, Castaneda AR, Reid LM.\u0026nbsp;Growth and development of pulmonary collateral vessels. \u003cem\u003eCirculation\u003c/em\u003e. 1981;64:1230\u0026ndash;1240.\u003c/li\u003e\n \u003cli\u003eKwak JG, Lee CH, Kim SH. Giant aneurysm of a major aortopulmonary collateral artery. \u003cem\u003eJ Thorac Cardiovasc Surg\u003c/em\u003e. 2014;148:e241\u0026ndash;e243.\u003c/li\u003e\n \u003cli\u003eJoynt MR, Lu JC, Bocks ML, Crowley DC. Ruptured aneurysm of a major aortopulmonary collateral. \u003cem\u003eEur Heart J\u003c/em\u003e. 2016;37:1777.\u003c/li\u003e\n \u003cli\u003eSharma A, Kumar S, Priya S. Ruptured aneurysm of major aortopulmonary collateral artery: management using Amplatzer vascular plug. \u003cem\u003eCardiovasc Diagn Ther\u003c/em\u003e. 2016;6:310\u0026ndash;314.\u003c/li\u003e\n \u003cli\u003eTatsumoto S, Kobayashi K, Mizuno Y, Nagata T. Rupture of a mediastinal collateral aneurysm associated with unilateral absence of pulmonary artery. \u003cem\u003eJ Vasc Surg Cases Innov Tech\u003c/em\u003e. 2024;11.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"the-egyptian-heart-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"tehj","sideBox":"Learn more about [The Egyptian Heart Journal](https://tehj.springeropen.com)","snPcode":"43044","submissionUrl":"https://submission.springernature.com/new-submission/43044/3","title":"The Egyptian Heart Journal","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Open","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"major aortopulmonary collateral artery, MAPCA aneurysm, computed tomography angiography, thoracic endovascular aortic repair, coil embolization, chest pain","lastPublishedDoi":"10.21203/rs.3.rs-9164305/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9164305/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBackground:\u003c/p\u003e\n\u003cp\u003eMajor aortopulmonary collateral arteries (MAPCAs) are anomalous systemic-to-pulmonary vessels typically associated with complex congenital heart disease. Isolated MAPCAs in adults without structural cardiac abnormalities are exceedingly rare, and aneurysmal degeneration is even more uncommon.\u003c/p\u003e\n\u003cp\u003eCase presentation:\u003c/p\u003e\n\u003cp\u003eWe report a 48-year-old man presenting with acute non-exertional chest pain. Computed tomography angiography (CTA) demonstrated a 2.6-cm saccular aneurysm arising from an isolated MAPCA originating from the proximal descending thoracic aorta and supplying the left lower lobe pulmonary artery. CTA delineated the vascular anatomy and excluded associated congenital cardiac abnormalities. Digital subtraction angiography confirmed a single systemic-to-pulmonary arterial communication. The patient underwent thoracic endovascular aortic repair with adjunctive coil embolization, resulting in complete aneurysm exclusion and symptom resolution.\u003c/p\u003e\n\u003cp\u003eConclusions:\u003c/p\u003e\n\u003cp\u003eThis case highlights the importance of recognizing isolated aneurysmal MAPCAs in adults, the value of CTA in diagnosis and procedural planning, and the effectiveness of endovascular therapy in preventing potentially life-threatening complications.\u003c/p\u003e","manuscriptTitle":"Isolated Aneurysmal Major Aortopulmonary Collateral Artery in a Structurally Normal Adult: Computed Tomography Angiography Diagnosis and Endovascular Exclusion","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-31 06:54:38","doi":"10.21203/rs.3.rs-9164305/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-05-03T21:36:47+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-02T06:46:25+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-01T07:59:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"81631258012541460888166757359161556148","date":"2026-04-22T19:47:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"250287909559709058136151739945762852623","date":"2026-04-22T02:47:28+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-01T04:09:10+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"165343287616373314120058457369583223779","date":"2026-04-01T03:27:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"2284948696751526912111859076711850751","date":"2026-03-27T01:40:40+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-27T00:46:49+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-23T01:15:27+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-23T01:14:46+00:00","index":"","fulltext":""},{"type":"submitted","content":"The Egyptian Heart Journal","date":"2026-03-19T02:56:32+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"the-egyptian-heart-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"tehj","sideBox":"Learn more about [The Egyptian Heart Journal](https://tehj.springeropen.com)","snPcode":"43044","submissionUrl":"https://submission.springernature.com/new-submission/43044/3","title":"The Egyptian Heart Journal","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Open","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7e1122f8-88fc-4ad9-bda6-b6dce41e9dfa","owner":[],"postedDate":"March 31st, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-05-03T21:36:47+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-02T06:46:25+00:00","index":33,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-01T07:59:19+00:00","index":32,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-11T21:54:53+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-31 06:54:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9164305","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9164305","identity":"rs-9164305","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}