Right coronary artery-right ventricle fistula with a rare giant thrombotic aneurysm: a case report and literature review

Introduction

Background

Coronary artery fistula (CAF) is an abnormally dilated and tortuous shunt arising from one coronary artery or its branches with an abnormal endpoint including cardiac chamber, artery, or vein. CAF is an uncommon coronary artery abnormality, with a reported incidence of 0.3% in patients at invasive angiography or 0.9% at coronary computed tomography angiography (CCTA) (1). CAF is usually congenital, representing a remnant primitive connection between coronary artery and cardiac chambers or vessels. It can also be acquired, which may be secondary to infective endocarditis, trauma, aortic dissection, endomyocardial biopsy, and interventional and surgical treatment (2). CAF can mainly be classified by the origin, drainage site, or the presence of accompanying anomalies, and the most common type is coronary-pulmonary artery fistula (3). In a few cases, the fistula may be accompanied by aneurysm formation, but giant aneurysm is rare.

Rationale and knowledge gap

The pathophysiology and clinical manifestations can vary between different types of CAF. Most cases of CAF are small and asymptomatic. The presence of dilated vessels, multiple origins, and origination from the proximal coronary artery could lead to increased left-to-right shunt, right ventricular volume overload, and “coronary steal” phenomenon, that would manifest as dyspnea, angina pectoris, and lower limb edema in patients. At present, complications other than fistula steal are paid insufficient attention, especially coronary artery dilatation, ulcer, dissection, aneurysm rupture, thrombosis, myocardial infarction, heart failure, and so on. It has been reported that coronary cameral fistula with a single origin is likely to be accompanied by aneurysms, especially for the type of CAF with a leakage to the right cardiac system. The underlying reason may be the low-pressure drainage site; this would increase the pressure between the origin and the endpoint, which would lead to persistent high flow and increase the risk of aneurysm formation (3). It is acknowledged that thrombosis formation could be present in an isolated giant coronary artery aneurysm (4), but it is seldomly reported that CAF can be accompanied by a giant aneurysm with thrombosis and possibly relevant to myocardial infarction. Cardiac magnetic resonance (CMR) is not only of great value in differential diagnosis, but also useful in the evaluation of myocardial ischemia and infarction. However, it has not received much consideration in clinical diagnosis and patient management.

Objective

We report a case of right coronary artery (RCA)-right ventricle (RV) fistula with a rare giant thrombotic aneurysm that was identified using multiple imaging examinations. The risk of embolism events and myocardial infarction was considerable, and surgical intervention was indicated. We present this case in accordance with the CARE reporting checklist (available at https://cdt.amegroups.com/article/view/10.21037/cdt-2025-104/rc).

Case presentation

A 51-year-old female had presented to the emergency department with stomachache, chest pain, and palpitation four years prior, without fever, nausea, emesis, diarrhea, cough, and expectoration. She had a history of high diastolic blood pressure, but hypertension had not been confirmed. The initial physical examination revealed a heart rate of 89 beats/minute and blood pressure of 158/96 mmHg. The lab examination indicated elevated cardiac troponin (1.04 ng/mL). Acute myocarditis was suspected; a subsequent electrocardiogram indicated incomplete right bundle branch block (Figure 1), and echocardiography showed dilatation of the RCA and a hypoechoic mass originating from the RCA (Figure 2, Video S1). Color Doppler flow imaging showed left-to-right shunt at the atrial septum. CCTA showed a dilated lumen of the proximal and middle RCA, and diffuse mixed atherosclerotic plaque with mild stenosis. The RCA diameter was 6.9 mm, connected to a mass (47.1 mm × 30.0 mm), which compressed the RV, together with contrast filling defects. Therefore, CCTA confirmed the diagnosis RCA-RV fistula with a giant thrombotic aneurysm (Figure 3). The patient was treated with trimetazidine for 5 days, and her symptoms of stomachache, chest pain, and palpitation disappeared; follow-up testing revealed complete normalization of cardiac troponin. Surgical closure of the fistula, aneurysm, and atrial septal defect (ASD) was suggested, but the patient refused and chose clinical follow-up. Over the 4-year follow-up, the patient had developed hypertension and experienced an ischemic stroke in 2021.

Figure 1 Electrocardiogram shows incomplete right bundle branch block.

Figure 2 The images acquired from echocardiography. (A) Dilatation (13 mm) of the right coronary artery (white arrow). (B) A hypoechoic mass (32 mm × 21 mm) adjacent to RV, which is connected to the right coronary artery (white arrow). (C) Color Doppler flow imaging shows blood flow (white arrow) of origination (red) and the mass (red and blue). RV, right ventricle.

Figure 3 The images acquired from coronary computed tomography angiography. (A) The first examination on 1 April 2019 shows the mass. (B) The second examination on 7 October 2023: calcification is seen and right ventricular diameter is increased. (C,D) Cinematic rendering reconstruction shows the relationship between the mass and the dilated right coronary artery, resembling a fruit growing on a coronary tree. RV, right ventricle.

Four years later, the patient presented to the department of cardiac surgery for the follow-up of CAF, without fever, dyspnea, palpitation, angina pectoris, and syncope. She had a heart rate of 75 beats/minute with a normal heart rhythm without murmur, and her blood pressure was 133/89 mmHg. CCTA examinations indicated dilatation of the RCA with diffuse mixed atherosclerotic plaque and mild stenosis. Scattered punctiform and nodular calcification was found in the aneurysm (46.7 mm × 29.3 mm), and the RV diameter was also increased. Cinematic rendering reconstruction showed the relationship between the mass and the coronary artery tree as if it was a fruit growing on the tree (Figure 3, Video S2). A left-to-right shunting jet of contrast was also revealed. Further CMR revealed a mass located at the right atrioventricular sulcus, with low signal intensity on cine and T1-weighted image (T1WI) sequence, inhomogeneous high signal intensity on T2-weighted image (T2WI) sequence, and deformation of the RV. However, the left and right ventricular ejection fraction was 63% and 60%, respectively, which indicated normal biventricular systolic function. No myocardial ischemia was indicated on rest perfusion imaging. Nodular enhancement on rest perfusion and inhomogeneous late gadolinium enhancement was revealed (Figure 4, Video S3). Subendocardial late gadolinium enhancement of the basal inferior wall was also found, without high signal intensity on T2WI sequence, which suggested chronic myocardial infarction. Considering the former stroke and myocardial infarction, the risk of complications still remained, and the patient finally accepted surgery. Subsequent surgical procedures confirmed RCA-RV fistula, stiffness of the ventricular wall, and compression of the anterior right ventricular wall by the aneurysm. The RCA-RV fistula was surgical closed, as well as the ASD. The patient was followed up for 1 year and 3 months without any major adverse cardiovascular events.

Figure 4 The images acquired from CMR. (A) Cine sequence shows a mass in the right atrioventricular sulcus and in front of right ventricular (yellow arrow). (B) T1WI shows low signal intensity of the mass (yellow arrow). (C) T2WI shows inhomogeneous high signal intensity of the mass (yellow arrow). (D) Inhomogeneous late gadolinium enhancement of the mass on four-chamber view (yellow arrow). (E) Short-axis view shows inhomogeneous late gadolinium enhancement of the mass (yellow arrow), and ischemic scar of basal lateral wall (red arrow). (F) Ischemic scar of basal lateral wall on four-chamber view (red arrow). CMR, cardiac magnetic resonance; T1WI, T1-weighted image; T2WI, T2-weighted image.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was provided by the patient’s relatives for publication of this case report and accompanying images. A copy of the written consent is available for review from the editorial office of this journal.

Discussion

Key findings

In this case, we provide a comprehensive assessment of CAF accompanied by an aneurysm with thrombosis formation via the integration of echocardiography, CCTA, and CMR. Echocardiography is useful in screening CAF. CCTA is important in the diagnosis and follow-up of CAF, especially for evaluating the organization of the thrombus, the morphology, position of aneurysms, and anatomical relationship with RV. Chronic myocardial infarction is also indicated by CMR displaying compressed RV but preserved ejection fraction.

Strengths and limitations

By means of multimodal imaging examination, the boundary, signal intensity of the mass, its origin, and relationship with RCA can be confirmed. CCTA is valuable in clearly depicting the location and anatomical relationship with RV by cinematic volume rendering reconstruction, which is a new and useful method in preoperative evaluation. CMR also provides additional information on differential diagnosis, myocardial viability, and biventricular function. In this case, the giant lesion also required differentiation with cardiac tumors, such as hemangioma and teratoma. Besides, subendocardial late gadolinium enhancement of the basal inferior wall strongly suggested chronic myocardial ischemia, which may be caused by the detachment of thrombus in the aneurysm, and this also suggests the risk of myocardial infarction in future. Another strength of CMR is the assessment of ventricular function, and it currently represents the gold standard method for right ventricular function evaluation. The lack of right ventricular function according to echocardiography and CCTA is a limitation in this case, although right ventricular function assessment is limited and not reliable by echocardiography and CCTA when compared with CMR. Another limitation is the lack of stress myocardial perfusion by CMR, for which myocardial ischemia could be caused by “coronary steal” in CAF patients.

Comparison with similar research

It is reported that a giant coronary artery aneurysm with thrombosis is rare (4), and the rarity of our case was even greater due to it being accompanied by CAF. During follow-up, the second CCTA revealed a new scattered punctiform and nodular calcification in the aneurysm, which also indicated the course and result of thrombus organization. CCTA with cinematic rendering is reported to be valuable in cardiovascular diseases, especially in CAF (5,6). In this patient with CAF accompanied by an aneurysm, noninvasive computed tomography (CT) cinematic rendering reconstruction played an important role in preoperative planning by clearly depicting the origin, drainage site, delineation, aneurysm, and compression of RV. In cases of CAF, long-term left-to-right shunt leads to right ventricular overload and right heart decompensation; rupture of the fistula or a connected aneurysm with successive hemopericardium would cause pericardial tamponade (7,8). However, the case presented herein was free of heart failure, the potential reasons may be that thrombosis in the aneurysm may decrease left-to-right shunt and progression of right heart disfunction, or that the organized thrombus also made the aneurysm more stable. Myocardial infarction is reported as a risk in patients with CAF and aneurysms (9) and postoperative patients that have undergone surgical interventional closure (10,11). In our case, we further reported that CAF and a thrombotic aneurysm could also indicate the risk of myocardial infarction. These findings also suggest the importance of anticoagulant therapy pre- and post-operative management.

Explanations of findings

CAF with a giant aneurysm is rare, and the pathogenesis of such aneurysms is still unclear. The potential factors include fragile smooth muscle, excessive arterial blood flow, aging, atherosclerosis, myxoid degeneration in the middle structure of malformed vessels, and the increased pressure difference between RCA (origin) and RV (endpoint) (3,12,13). Thrombus formation in a giant aneurysm of CAF is also complex, which may be due to the disorder of hemodynamics inside the aneurysm, or factors such as plaque rupture (4). It should be also noted that in this rare case, the occurrence of myocardial ischemia or infarction was possible, although the calcification of the thrombus was indicated in the second CCTA. Thrombus formation within the aneurysm occluded most of the aneurysm, and was similar to that of transcatheter or surgical closure of CAF, but also prone to cardiac ischemia. In this case, the patient was also found to have chronic subendocardial infarction in the basal inferior wall, which was likely the thromboembolism from the thrombotic aneurysm. There was still a little blood flow within the aneurysm, and the dislodged thrombus fragments had the potential to cause myocardial infarction. In addition, echocardiography and CCTA indicated ASD, which is related to right ventricular overload and cardiovascular events, and the patient experienced a stroke event during the second CCTA examination, which may indicate that stroke was the complication of ASD.

Implications and actions needed

Our case report highlights that in patients with CAF and a giant thrombotic aneurysm, a persistent risk of myocardial infarction still exists during the follow-up period. Given that CAF is frequently associated with congenital heart disease and ASD in particular predisposes to stroke, the risk of cardiovascular events is increased. Follow-up remains imperative even after aneurysm closure, for the potential complications include post-procedural endocarditis, CAF recurrence, and progressive vasculopathy of the dilated coronary artery (such as plaque formation, thrombosis, ulceration, and dissection). Additionally, right ventricular function should also be routinely assessed during follow-up.

Conclusions

In this rare CAF case, we reported a giant aneurysm with thrombus formation and organization during the CCTA follow-up. The combined application of multimodal imaging yields significant value in the follow-up, preoperative assessment, and complication evaluation of CAF with aneurysm and ASD. Notably, cinematic volume rendering reconstruction and multiparametric CMR imaging significantly enhance visualization to improve the diagnosis and assessment of complications.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://cdt.amegroups.com/article/view/10.21037/cdt-2025-104/rc

Peer Review File: Available at https://cdt.amegroups.com/article/view/10.21037/cdt-2025-104/prf

Funding: This study was supported by the Medical and Health Research Project of Zhejiang Province (No. 2025KY1745), and the project grant from the Jinhua Municipal Central Hospital (No. JY2023-2-02).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://cdt.amegroups.com/article/view/10.21037/cdt-2025-104/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was provided by the patient’s relatives for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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