Surgical Treatment of an Aneurysmal Coronary Artery Fistula between the Left Coronary Artery and Right Atrium: A Case Report

Abstract

A coronary artery fistula (CAF) is an abnormal vascular connection between the coronary arteries and the cardiac chambers or major vessels. Although rare, CAFs can lead to substantial coronary morbidity and mortality. This study outlines the surgical management of a CAF originating from the left coronary artery and connecting to the right atrium, in a patient experiencing angina with a marked left-to-right shunt. The surgical approach involved ligation of the coronary artery and reduction of the aneurysmal portion, resulting in the patient’s uneventful recovery.

Case report

A 52-year-old woman with a long history of atypical chest pain was referred to Asan Medical Center for evaluation of a cardiac mass, as diagnosed by echocardiography. An initial chest X-ray revealed mild cardiomegaly with a cardiothoracic ratio of 55%, while electrocardiography displayed a normal sinus rhythm without meaningful ST-T changes. Initial laboratory tests indicated normal cardiac enzyme levels, with creatine kinase-MB at 0.2 pg/mL and troponin I at 10 pg/mL. Transthoracic echocardiography demonstrated a normal ejection fraction (57%) and increased dimensions of the left ventricular and left atrial chambers. The parasternal short-axis view revealed aneurysmal dilation of the left coronary artery (Fig. 1). Color Doppler interrogation showed abnormal continuous flow from the dilated left coronary artery to the right atrium (Fig. 1). For further evaluation, we conducted coronary artery computed tomography with 3-dimensional reconstruction and coronary angiography. The left anterior descending artery (LAD) and left circumflex artery (LCX) were found to originate from the dilated left main artery and drain into the right atrium above the coronary sinus ostium; additionally, a saccular aneurysm (diameter, 34×37 mm) was observed at the distal part of the fistula (Fig. 2). After confirmation of the course of the CAF, cardiac magnetic resonance imaging (cMRI) was performed to assess the morphological and functional characteristics of the left-to-right shunt, revealing a ratio of pulmonary to systemic blood flow (Qp/Qs) of 1.93.

Fig. 1.

(A, B) Transthoracic echocardiography. (A) The parasternal long-axis view reveals a coronary artery fistula (indicated by the * symbol) extending toward the left atrium (LA). (B) The parasternal short-axis view shows a markedly dilated coronary artery fistula (indicated by the * symbol). (C, D) Transthoracic Doppler echocardiography. (C) Color Doppler imaging illustrates drainage into the right atrium (RA) from the left coronary artery (denoted by the arrow). (D) Continuous jet flow is depicted. RV, right ventricle; AV, aortic valve; LV, left ventricle; RCC, right coronary cusp; LCC, left coronary cusp; NCC, non-coronary cusp.

Fig. 2.

(A) Coronary artery computed tomography indicates drainage of the dilated left main coronary artery (LM) into the right atrium (RA), along with a saccular aneurysm (SA) formed at the distal part of the fistula. (B) A 3-dimensional reconstruction image reveals a coronary artery fistula. (C, D) On coronary angiography, the left anterior descending artery (LAD) and left circumflex artery (LCX) are shown to originate from the dilated LM. PA, pulmonary artery; AV, aortic valve; LA, left atrium; RCA, right coronary artery.

Due to the risk of saccular aneurysm rupture and the potential for migration of the closure device, we decided to proceed with surgery rather than percutaneous transcatheter closure. The patient underwent elective open-heart surgery via a median sternotomy. Ascending aorta and bicaval cannulation was performed. Following aortic cross-clamping, cardiac arrest was induced using antegrade cardioplegia. The CAF was readily identified, and the ostium of the left main coronary artery was found to be enlarged to approximately 1.5 cm. Fistulotomy was performed with a longitudinal incision made at the distal part of the fistula, where the LAD and LCX originated (Fig. 3). The wall of the fistula had thickened to a degree comparable to that of the aorta, and it was not anticipated to expand further; thus, we opted to preserve the proximal part of the left main artery. The fistula was divided, and each end was obliterated. At the edges of the proximal end, a round suture was employed to prevent thrombus formation, which could obstruct the left coronary artery and result in life-threatening complications. The distal portion of the fistula was left in place, as it was expected to occlude naturally through thrombosis over time. The surgical method described herein contributed to a meaningful reduction in operative time, and the patient was smoothly weaned from cardiopulmonary bypass. Following the procedure, the patient was immediately transferred to the intensive care unit and then to the general ward the next day, all without major problems. The patient was discharged in stable condition 5 days after surgery. Postoperative computed tomography revealed a reduction in the size of the distal part of the fistula with minimal contrast enhancement, and with probable retrograde flow from the right atrium (Supplementary Fig. 1). After discharge, the patient continued warfarin treatment with an international normalized ratio target of 2.0 for 3 months, after which the treatment was switched to dual antiplatelet therapy. The patient remained asymptomatic and free of any adverse events through the last outpatient visit, 6 months after surgery.

Fig. 3.

(A, B) A longitudinal incision (indicated by the arrow) was made at the distal part, where the left anterior descending artery (LAD) and left circumflex artery (LCX) originated. (C) A round suture was applied at the proximal end of the fistula. RCA, right coronary artery.

We obtained informed consent from the patient for the publication of her clinical details and images within this case report.

Discussion

A CAF is an abnormal vascular connection between the coronary arteries and the cardiac chambers or any of the major vessels. CAFs are uncommon, with an incidence of 0.002% in the general population, and account for 0.4% of all cardiac malformations. Despite their rarity, CAFs can cause substantial coronary morbidity and mortality, leading to angina, syncope, congestive heart failure, myocardial infarction, and sudden death [1]. While most CAF cases are asymptomatic, some patients may experience symptoms such as angina, exertional dyspnea, and arrhythmia. The optimal timing and treatment methods for CAF remain topics of debate; however, consensus exists that symptomatic or large CAFs warrant intervention, typically through surgical ligation or percutaneous transcatheter closure [2].

CAFs can be classified based on their origin, distribution, or termination. Sites of origin include the right coronary artery (in 50%–60% of cases), the LAD (25%–42%), the LCX (18.3%), or both coronary arteries (5%). Termination points, or drainage sites, include the right ventricle (in 14%–40% of cases), the right atrium (19%–26%), the left ventricle (2%–19%), and the pulmonary artery (15%–20.2%) [3]. Sakakibara et al. [4] outlined 2 types of CAF. The proximal type is characterized by a fistula originating within the proximal third of the coronary arteries, causing dilation of the proximal coronary segment up to the fistula’s origin, while the distal segment remains unaffected. In contrast, the distal type involves dilation along the entire length of the coronary artery, with the fistula typically terminating at the right side of the heart. The termination site of a CAF is more meaningful than the origin site. Two classifications exist based on termination site: coronary cameral fistula, which connects the coronary artery to a cardiac chamber, or coronary arteriovenous fistula, which connects to either a pulmonary or systemic artery [4].

The so-called coronary steal phenomenon is considered the primary pathophysiological issue in CAF. This condition arises when elevated pressure within the coronary artery exerts an excessive volume load on the low-resistance receiving chamber due to a diastolic pressure gradient. This can lead to angina or myocardial ischemia during activities that increase oxygen demand [3]. When the fistula involves a left-to-right shunt, draining into the systemic venous circulation, it can cause pulmonary hypertension and volume overload in both ventricles. Conversely, a left-to-left shunt, where the fistula drains into the left atrium or pulmonary vein, leads to increased left heart volume overload. If a significant shunt remains untreated, it may progress to high-cardiac-output heart failure. Early anatomic correction should be considered when the shunt amount is significant, as evidenced by a Qp/Qs ratio greater than 1.5 [2]. Shmueli et al. [5] described the case of a patient with a fistula extending from the left coronary artery to the coronary sinus, who presented with congestive heart failure and a significant left-to-right shunt (Qp/Qs=2.5). Following transcatheter closure of the fistula, the patient displayed an improvement in symptoms but also experienced complications from a myocardial infarction. Similarly, Sandor et al. [6] reported a patient with a fistula extending from the left circumflex coronary artery to the coronary sinus, along with a significant left-to-right shunt (Qp/Qs=2.159) and congestive heart failure. After undergoing fistula ligation, the patient was discharged with improved cardiac function.

Transthoracic echocardiography is regarded as the primary imaging modality for patients with suspected CAF. While it can present challenges in visualizing the entire coronary anomaly, this technique offers critical insights into associated cardiac abnormalities and the corresponding structural and functional status [7]. Computed tomography angiography is the principal diagnostic method for identifying coronary artery anomalies. Cardiac catheterization not only facilitates the hemodynamic assessment of the fistula structure and flow but also serves as a means of therapeutic intervention [3]. Finally, cMRI is an excellent noninvasive imaging technique for evaluating cardiovascular shunts. In the present case, the Qp/Qs ratio was determined using cMRI, contributing to the decision to proceed with prompt surgical intervention.

The management of CAFs remains a topic of debate, as no randomized studies have been published regarding the optimal treatment approach. To date, only case reports have documented a variety of techniques for repairing aneurysms or fistulas. These techniques include the use of covered stents, coil embolization, the placement of Amplatzer devices, and surgical bypass procedures. Percutaneous transcatheter closure is the preferred method for cases characterized by a single narrow drainage site, a fistula originating near the proximal end, and the absence of concomitant cardiac diseases. Surgical intervention is typically advised for patients with large symptomatic fistulas, distal vessel dilatation, multiple connections, or tortuous arterial pathways, along with those who present with concomitant cardiac anomalies [8].

At present, no standardized guidelines exist for post- treatment follow-up. Computed tomography may serve as the simplest and least invasive approach, with the option of coronary angiography if issues are detected during the monitoring period. Potential complications following treatment include persistent dilatation or aneurysmal changes at the ostium and within the coronary arteries, as well as thrombus formation, which can lead to myocardial ischemia and infarction [8]. Risk factors for thrombus formation after treatment include advanced age, large distal CAFs, and the absence of anticoagulant therapy [9].

In the present case, the patient presented with angina symptoms and a significant left-to-right shunt, necessitating early intervention due to the risk of progression of heart failure. Given the thickened fistula wall, a simple ligation was performed without the need for fistulectomy. Had the proximal part of the left main artery been removed, coronary artery bypass grafting (CABG) would have been imperative. However, due to the anticipated surgical complexity and the superior flow expected in the native left main artery compared to graft flow, we opted not to proceed with CABG. Consequently, we avoided complex procedures such as graft harvesting and vascular anastomosis, thereby meaningfully reducing the operation time. However, leaving the fistula intact in a young patient poses the risk of aneurysm progression and fistula recurrence, necessitating a thorough assessment of the residual fistula before proceeding. Moreover, when opting to preserve a portion of the fistula, regular monitoring via computed tomography is imperative, and this requirement should be factored into the decision-making process.

No guidelines have yet been established for the management of CAF. Additional research is required to determine the most effective intervention timing based on size and symptoms, as well as to establish whether surgery or percutaneous transcatheter intervention is the superior treatment approach. A review of the existing literature indicates that a left-to-right shunt with Qp/Qs of 1.5 or greater can lead to heart failure, necessitating timely intervention. In scenarios similar to the present case, where percutaneous transcatheter intervention is not feasible due to factors such as the presence of a large saccular aneurysm, prompt surgical treatment should be considered. In our case, the robustness of the fistula wall reduced the likelihood of further enlargement or rupture. This factor influenced the decision to complete the procedure with a simple ligation, leaving a portion of the fistula intact and eliminating the need for CABG. To prevent thrombus formation within the residual fistula, a round suture was applied. Additionally, anticoagulation therapy was initiated following surgery. Postoperatively, the patient fared well, exhibiting no complications such as heart failure or thrombus-related issues. Our case should be considered a valuable reference for formulating an optimal treatment strategy.

Supplementary materials

Supplementary materials can be found via https://doi.org/10.5090/jcs.23.079. Supplementary Fig. 1. Postoperative computed tomography image.

Funding Statement

Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.