Bilateral Coronary Artery to Pulmonary Artery Fistulae: A Very Rare Anomaly

Coronary artery fistulas (CAFs) are a rare group of coronary anomalies which result in an abnormal connection between a coronary artery and either a cardiac chamber or any great vessel, most commonly pulmonary artery. They are mostly congenital but can be acquired and usually diagnosed incidentally. Although single vessel fistulas are far more common and have been reported routinely in literature, bilateral or multiple fistulas are extremely rare. Here, we describe a very unique case of bilateral coronary artery fistulas in a patient, with fortunately no significant hemodynamic consequences.

70 y/o male with a past medical history of diabetes, hypertension, hyperlipidemia, morbid obesity, family history of early coronary artery disease (CAD) and no known prior CAD who presented to the hospital for an episode of severe, sub-sternal chest pain associated with shortness of breath (SOB) and diaphoresis. Vital signs were normal, ECG and physical exam were unremarkable and lab work revealed normal CBC, serum chemistries, and negative troponins. Subsequently, patient underwent nuclear stress testing and was found to have a medium to large shadow, suggestive of possible ischemia or artifact in the lateral and basilar walls.

Left heart catheterization was then performed which revealed non-obstructive coronary arteries but other incidental coronary anomalies. On multiple views, there was noted to be a fistulous connection between the proximal left anterior descending artery (LAD) and the main pulmonary artery (Figure 1). A fistulous connection was also evident between the conus branch of the right coronary artery (RCA) to the main pulmonary artery (Figure 1 & 2).

Right heart catheterization revealed mild pulmonary hypertension with the mean PA pressure of 27 mmHg. Cardiac index was normal at 2.38 L/min/m2. Oxygen saturation in right atrium (RA) was 62.7%, main pulmonary artery was 62.9%, right pulmonary artery was 62.4% and left pulmonary artery was 64.2%, suggestive of no significant mixing of blood secondary to left to right shunt. RA/right ventricular angiogram did not reveal any fistulous connection. Dedicated coronary CT angiogram was then obtained, which did show evidence of a small fistulous communication between the proximal LAD and the main pulmonary artery (Figure 3). A second fistula was seen between the conus branch and the main pulmonary artery (Figure 4).

Coronary artery fistula (CAF), a major coronary anomaly by Ogden classification [1], is an abnormal connection between a coronary artery and any of the great vessels (pulmonary artery, superior vena cava, pulmonary veins or coronary sinus) or either of the cardiac chamber. First described by Krause in 1865 [2, 3], they are thought to arise due to the failure of intramyocardial trabecular sinusoids during the early embryonic period [4,5]. CAFs are most often congenital but can also be acquired from trauma, infection, iatrogenic injury (from congenital cardiovascular surgeries, catheter directed myocardial biopsy) [2,4].

A fistula arising from LAD and conus branch, with termination into the pulmonary artery, as in our patient, is an extremely rare finding [9]. CAFs are thought to be present in 0.002% of the general population, with single fistulas being most common and comprising 74% to 90% of all CAFs [4,6,7]. Multiple fistulas are significantly rarer, occurring in 10.7% to 16% of all CAFs, with involvement of both coronaries being less than 5% [4,6,7]. Drainage into pulmonary artery occurs with more frequency with bilateral fistulas (56%) than unilateral fistulas (17%) [8,9].

CAFs are typically found incidentally on coronary angiography, such being the case in our patient. With the advent of advanced CT angiography, prevalence of CAFs is increasing. In a retrospective study of 17,548 patients who underwent CTA of the heart, the incidence of CAF was 0.19% [10]. Pulmonary artery was found to be the most common site of drainage (84.8%) [10]. Most CAFs are small and do not result in significant hemodynamic issues or patient between proximal LAD (red arrow) and pulmonary RCA showing fistulous connection (yellow arrow) artery. between conus branch (red arrow) and pulmonary artery.

Complaints [12]. Large fistulas with significant flow can result in volume overload and pulmonary hypertension. Coronary ischemia can also result from excessive shunting of blood away from the coronary blood flow [12]. Most patients are asymptomatic, but significant fistulae can cause syncope or angina [12]. The main indications for closure for CAFs are patient symptoms, particularly congestive heart failure, coronary ischemia, or significant shunting [10]. Treatment options include observation, transcatheter embolization, or surgical intervention. Transcatheter closure, due to its less invasive nature is the primary modality recommended for symptomatic patients or asymptomatic patients with high risk findings for future complications, but surgical closure is preferred in complicated or tortuous cases [7,11]. In our patient, due to the asymptomatic nature of his bilateral fistulae, he was managed expectantly with regular outpatient cardiology follow up.

Coronary artery fistula (CAF) is a rare anomaly, most often congenital and usually found incidentally. Frequently, they are unilateral, and they arise from the left coronary system and empty into the pulmonary artery. We describe a very rare of bilateral coronary artery fistula to the pulmonary artery. Percutaneous closure or surgical closure are the preferred modalities of intervention in symptomatic patients.

None.

No Conflicts of interest.

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