Incidental left anterior descending coronary artery-pulmonary artery fistula with a fistulous aneurysm: CT angiography characterization and management

Abstract

Coronary artery fistulas (CAFs) are rare vascular anomalies characterized by an abnormal connection between a coronary artery and a cardiac chamber or the great vessels. The coronary-pulmonary artery fistula (CPAF) is the most common subtype, often detected incidentally on cardiac imaging but occasionally leading to significant clinical consequences. CPAFs are most often congenital but can also be acquired due to trauma or iatrogenic causes. Diagnosis relies on imaging, including CT angiography (CTA) for detailed anatomical assessment. Management decisions depend on symptoms and risk of complications. We present a 73-year-old woman with a history of hypertension, hyperlipidemia, and prior tobacco use, referred for evaluation of a CPAF arising from the left anterior descending (LAD) artery with a saccular aneurysm in the course of the fistula. From the cardiovascular standpoint, the patient was asymptomatic. Given the asymptomatic condition and absence of hemodynamic disturbance, conservative management with annual imaging follow-up was recommended. This case highlights the importance of correlating imaging findings with clinical context through multimodal evaluation and personalized management in patients with incidentally discovered CPAFs, particularly when aneurysmal change is present. Careful longitudinal follow-up is essential to monitor interval growth and assess hemodynamic stability, which dictate the appropriate course of management.

Introduction

Coronary artery fistulas (CAFs) are rare vascular anomalies characterized by an abnormal connection between the coronary arteries and a cardiac chamber or great vessel. CAFs can be congenitally present due to abnormal embryonic development or acquired later in life, mainly resulting from trauma or iatrogenic causes [1]. CAFs are often found incidentally during cardiac imaging, though it can lead to significant clinical consequences in symptomatic cases [2]. Common symptoms of CAFs include dyspnea, angina, and even progressive heart failure [3]. CAFs most commonly form with the pulmonary arteries, bronchial arteries, and cardiac chambers. Coronary-pulmonary artery fistulas (CPAFs) are the most common subtype of CAF, accounting for approximately 77% of CAFs [4]. Although many cases of CPAFs present asymptomatically, they are also subject to severe clinical complications such as ischemic heart disease, pulmonary hypertension, congestive heart failure, and aneurysmal rupture [5].

It has been demonstrated that most fistulae are stable in size, but some may grow slowly over time [6]. Treatment options for CPAFs include surgical ligation or catheterized closure, but management for asymptomatic cases remains disputed [1]. We report the case of a 73-year-old woman with a CPAFs and an aneurysm within the fistulous tract. We highlight the importance of correlating imaging with clinical considerations in the diagnosis and management of this rare comorbidity.

Case report

A 73-year-old woman was referred to our institution for evaluation of a CPAFs with aneurysmatic change. She disclosed a history of smoking with cessation over 20 years ago, hyperlipidemia, hypertension, and obstructive sleep apnea. She reported occasional episodes of transient ischemic attack (TIA) for which she takes rivaroxaban. She had previously undergone a series of transthoracic echocardiography (TTE) and CT angiography (CTA) of the chest, abdomen, and pelvis revealing a 4.3 cm ascending aortic aneurysm. It was also incidentally discovered that she had a 0.9 × 1.0 × 1.0 cm aneurysm within a fistula arising from the LAD, for which she was then referred to our institution. The patient presented asymptomatically from a cardiovascular perspective. She denied any exertional dyspnea, orthopnea, paroxysmal nocturnal dyspnea, angina, lightheadedness, dizziness, syncope, lower extremity edema, or palpitations. She reported a generally active lifestyle with no complaints of pain or symptoms at evaluation. It was noted that her father had an abdominal aortic aneurysm, and her brother has an ascending aortic aneurysm. No other family history of heart disease was disclosed. The patient’s blood pressure was 101/70 mmHg. Jugular venous and pulmonary artery pressures were normal. Auscultation of the heart was notable for regular rhythm with normal S1 and S2 pulses. No murmurs, rubs, or gallops were observed. The bilateral radial and dorsalis pedis pulses were 2+. No peripheral edema was observed. EKG showed normal sinus rhythm with left axis deviation and low voltage QRS. Anterior myocardial infarction could not be ruled out, and no signs of right heart dilatation were observed. CTA was performed and demonstrated the fistula from the LAD to the main pulmonary artery measuring 2.5 mm in diameter. The known aneurysm within the fistulous tract was appreciated and scattered coronary calcifications were noted (Fig. 1). On TTE, the right ventricle was normal in size with normal systolic function. Tricuspid regurgitation (TR) was trace with TR Vmax 2.1 m/s (TR peak gradient 17.7 mmHg). As assessed from the TR jet, the pulmonary artery systolic pressure (PASP) is 18-22 mmHg, indicating non-elevated echo-estimated pulmonary pressures. No intracardiac shunt was identified by color doppler. Left ventricle ejection fraction (LVEF) was estimated to be 65% with normal regional wall motion and normal diastolic indices (lateral E/e′ 9.6; septal E/e′ 12.5). Aortic sclerosis was noted. Right heart catheterization and stress testing were not performed. The patient was discharged with plans for repeat imaging in 1 year to monitor aneurysm growth. The patient was stable at the 1-year follow-up with no symptoms, and CTA showed no change in size or morphology of her CPAF and aneurysm.

Fig 1.

A 73-year-old woman with a history of smoking, hypertension, and transient ischemic attack presenting for evaluation of a CPAF with aneurysm. Contrast-enhanced CTA imaging of the heart in the axial (A) and coronal (B) views with volume and cinematic rendering (C-H) revealed a fistula originating at the LAD and terminating in the main pulmonary artery (arrows—B, E, G). A stable, saccular aneurysm measuring 0.9 × 1.0 × 1.0 cm was observed within the fistulous tract (arrows—A, C, D, F, H). No change in aneurysm size was noted since previous imaging.

Discussion

Etiology/Genetics

This article reviews a case of a rare CPAFs with a concurrent aneurysm. Coronary artery fistulae are characterized by abnormal communications between the coronary arteries and other cardiovascular structures. The prevalence of coronary artery fistulae is approximately 0.9% among patients who have undergone coronary CTA [4]. The most common CAF subtype is the CPAFs, accounting for an estimated 77% of CAFs [4]. Other known types of coronary fistulae include those with cardiac chambers, bronchial arteries, and the superior vena cava. Approximately 90% of CAF cases involve a singular fistula, but some cases with multiple fistulae have been reported [7,8]. In the present case, a CPAF arising from the LAD was identified, as well as a saccular aneurysm within the course of the fistula. Development of an aneurysm within the fistulous tract—although less common with prevalence estimated at 23% in systemic analyses of CPAF—is believed to be caused by the low-pressure shunts to the drainage site [5,9]. Aneurysmal CPAFs have been linked to increased risk of rupture, thrombosis, or myocardial ischemia, particularly in older patients or in those with hypertension or atherosclerosis, which are present in our patient. Coronary artery fistulae are most commonly congenitally present due to abnormal embryonic development. However, they can also be developed due to trauma, disease, or iatrogenic causes. Coronary vasculitis, myocardial infarction, and different types of cardiomyopathies may lead to CAF development [10,11]. Iatrogenic causes of CAFs include coronary artery bypass grafting, invasive cardiac angiography, valve replacements, device implantations, or biopsies [12]. It is unknown whether this patient’s CPAF was congenitally present or acquired as it was incidentally discovered on imaging.

Imaging

Cardiac CTA and coronary angiography are well-established modalities for detecting CAF and for accurately delineating their origin, course, and termination. Many CAFs are small and found incidentally during coronary angiography. It has also been noted that the increased usage of multi-detector CT for chest and cardiac imaging may contribute to the common incidental discovery of CAF [13]. Furthermore, volume- and cinematic-rendered images obtained from three-dimensional CT datasets offer a detailed visualization of cardiovascular anatomy and facilitate comprehensive characterization of CAFs (Fig. 1). Multiplanar reformation is also often employed to visualize the origin and termination of coronary artery fistulae [14]. While CTA and coronary angiography excel in anatomic definition, assessment of the hemodynamic significance of CAFs typically requires complementary physiologic evaluation, such as echocardiography, invasive hemodynamic measurements, or functional stress imaging [9]. Nevertheless, imaging remains a key modality to evaluate the origin and complexity of CAFs. In cases where CAFs drain into low-pressure heart chambers, imaging becomes a challenge as significant contrast dilution renders coronary angiography suboptimal [15].

In our case, follow-up CTA demonstrated a 2.5 mm tract originating from the bifurcation of the LAD and terminating at the main pulmonary artery. The known saccular aneurysm was observed within the fistula. No changes in the fistula or aneurysm sizes were noted over the course of 1 year. Calcified plaques of the proximal LAD were appreciated with minimal stenosis. Calcified plaques at the origin of the large diagonal branch exhibited mild stenosis (30%-40%) of the diagonal branch. No dilation of cardiac chambers was observed, and the heart was otherwise unremarkable. Calcium scores for the LAD and in total were 358.4 and 385.8, respectively. TTE further complemented CTA by excluding right heart dilatation and volume overload, indicating no significant shunt or hemodynamic compromise. This integration of structural and functional assessment is crucial in distinguishing physiologically silent CPAFs from those requiring intervention.

Diagnosis and management

Most adult patients with CAFs present asymptomatically. Fewer pediatric patients are asymptomatic compared to adults [16]. Coronary artery fistulae are initially evaluated with auscultation of a continuous murmur. Early diagnostic exams may include EKG or chest radiography. However, further evaluation is typically required for a sufficient diagnosis, including TTE, coronary angiography, and coronary catheterization. The most common clinical presentation of CAF is a continuous heart murmur. If symptoms do manifest, most patients present with dyspnea and right ventricular enlargement owing to fistulous growth and increased left-to-right shunting [17].

Coronary steal syndrome occurs when blood is shunted into low-pressure circulation, such as the right chambers of the heart or the pulmonary arteries [18]. The likelihood of coronary steal syndrome is correlated to vascular resistance in the fistula, often determined by fistula diameter and tortuosity [19]. Coronary steal syndrome may result in ischemia, exertional dyspnea, hypotension, or myocardial infarction and remains a concern in patients with CAFs. Other common symptoms include fatigue, orthopnea, angina, arrhythmias, myocardial ischemia, or myocardial infarction. Common etiologies in the differential diagnosis of CAFs include patent ductus arteriosus, pulmonary arteriovenous fistula, internal mammary artery to pulmonary artery fistula, acute myocardial ischemia, and various arrhythmias [16]. It is crucial to exclude other possible etiologies as intervention for CAFs is only recommended in patients with hemodynamically significant left-to-right shunt, congestive heart failure, or myocardial ischemia [1].

Various factors including size of the fistula, hemodynamic changes on echocardiography, ischemic status, and other cardiac abnormalities influence whether conservative or invasive techniques are used in cases that require intervention. The most common surgical treatment is fistula ligation; however, endovascular procedures may be appropriate in certain cases [20]. It has been shown that CAF ligation procedures may be complicated by post-procedural myocardial infarction, vessel trauma, and vessel dissection [21,22]. Surgical intervention should therefore be employed only when necessary to reduce the risk of serious complications. Common clinical indicators that may warrant surgical ligation include regional ischemia at the feeder artery, CAF-related arrhythmia, endarteritis, vessel rupture, cardiac chamber dilation, and ventricular dysfunction. Antiplatelet agents and/or anticoagulants may be offered in tandem with periodic follow-up evaluation as a conservative treatment protocol.

In the present case, a conservative surveillance-based approach was chosen. The fistula was small in caliber, with no evidence of hemodynamically significant left-to-right shunting on echocardiography and no associated right heart dilation. The patient was asymptomatic, with no clinical evidence of coronary ischemia to suggest coronary steal. Consequently, neither invasive hemodynamic assessment (right heart catheterization) nor noninvasive ischemia testing was pursued, given the absence of noninvasive findings indicating a significant left-to-right shunt or right-sided volume overload. Although the presence of an associated aneurysm raises concern for rupture risk, the aneurysm was modest in size and demonstrated stability on serial imaging, indicating a low short-term risk. Annual gated cardiac CTA was recommended to reassess the size of the ascending aortic aneurysm and to monitor interval changes in the CAF and associated aneurysm. Intervention would be reconsidered in the event of aneurysm enlargement, fistula growth, development of right-sided chamber dilation, new ischemic symptoms, or changes in ventricular function.

Conclusion

In conclusion, this case demonstrates that management of CPAFs requires integration of both imaging findings and clinical indicators rather than relying solely on either assessment. CTA precisely delineated the fistulous anatomy and aneurysmal morphology, while echocardiography provided key functional and hemodynamic insights. In asymptomatic patients, stable clinical and radiological features justify a conservative surveillance approach instead of invasive surgery. In CPAFs, particularly those with aneurysmal change, correlation between radiologic findings, hemodynamic evaluation, and clinical presentation serves a critical role in distinguishing stable lesions from those at risk of ischemia, rupture, or progressive shunting. Ongoing longitudinal follow-up is vital to identify aneurysm growth or hemodynamic changes that may necessitate timely intervention.

Patient consent

The authors declare that written informed consent was obtained from the patient.