eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiology

Coronary Artery Fistula

Author: Andrew N Pelech, MD, Professor, Department of Pediatrics, Medical College of Wisconsin; Director of Cardiac Catheterization Laboratory, Cardiology Research Focus and Cardiology Database, Director of Herma Heart Center Clinical Research, Children's Hospital of Wisconsin; Chairman of Wisconsin Pediatric Cardiac Registry
Contributor Information and Disclosures

Updated: May 28, 2009

Introduction

Background

Within the context of coronary artery anomalies, coronary fistulae are classified as abnormalities of termination. A coronary artery fistula (CAF) involves a sizable communication between a coronary artery, bypasses the myocardial capillary bed, and enters either a chamber of the heart (coronary-cameral fistula)¹ or any segment of the systemic or pulmonary circulation (coronary arteriovenous fistula). The pathophysiology of these lesions is identical, and they are often collectively termed coronary arterial-venous fistulae (CAVFs). A coronary artery connection to the pulmonary artery (coronary-pulmonary artery fistula) may also be considered under this grouping; however, if a named coronary artery arises directly from the pulmonary trunk with absence of a direct aortic connection, this is classified as an anomalous origin of the coronary artery from the pulmonary artery.²

Maude Abbott published the first pathological account of this condition in 1908. The first successful surgical closure of a coronary fistula was performed in 1947 by Bjork and Crafoord in a patient with a preoperative diagnosis of patent ductus arteriosus.

Pathophysiology

The pathophysiologic mechanism of coronary artery fistula is myocardial stealing or reduction in myocardial blood flow distal to the site of the coronary artery fistula connection. The mechanism is related to the diastolic pressure gradient and runoff from the coronary vasculature to a low-pressure receiving cavity. If the fistula is large, the intracoronary diastolic perfusion pressure progressively diminishes.³

The coronary vessel attempts to compensate by progressive enlargement of the ostia and feeding artery. Eventually, myocardium beyond the site of the fistula's origin is at risk for ischemia, which is most frequently evident in association with increased myocardial oxygen demand during exercise or activity. With time, the coronary artery leading to the fistulous tract progressively dilates, which, in turn, may progress to frank aneurysm formation, intimal ulceration, medial degeneration, intimal rupture, atherosclerotic deposition, calcification, side-branch obstruction, mural thrombosis, and, rarely, rupture.

The factors that determine the hemodynamic significance of the fistulous connection include the size of the communication, the resistance of the recipient chamber, and the potential for development of myocardial ischemia. Occasionally, high output congestive heart failure has been described.

Anatomy

Normally, 2 coronary arteries arise from the root of the aorta and taper progressively as they branch to supply the cardiac parenchyma. A fistula exists if a substantive communication arises that bypasses the myocardial capillary phase and communicates with a low-pressure cardiac cavity (atria or ventricle) or a branch of the systemic or pulmonary systems.

Normal thin-walled vessels exist at the arteriolar level that may drain into the cardiac cavity (arteriosinusoidal vessels) and venous communications (thebesian veins) to the right atrium. These small vessels do not steal significant nutrient flow and do not constitute fistulous connections. Fistulae are usually large (>250 mm) and dilated or ectatic, and they tend to enlarge over time. Often, the limits of what constitutes a fistula and what constitutes a normal vessel are debated.

Most fistulae arise from the right coronary artery (60%) and terminate in the right side of the heart (90%). The most frequent sites of termination, in descending order, are the right ventricle, right atrium, coronary sinus, and pulmonary vasculature. Coronary fistula communications may appear in the context of other congenital cardiac anomalies, most frequently in critical pulmonary stenosis or atresia with an intact interventricular septum and in pulmonary artery branch stenosis, coarctation of the aorta, and aortic atresia. In the setting of cardiac outflow obstruction, the term coronary-sinusoidal connections is used. Although most often congenital, a coronary fistula rarely may arise as a consequence of surgical resection of obstructing right ventricular muscle bundles (as in tetralogy of Fallot), endomyocardial biopsy, or penetrating or blunt trauma.

Embryology

Coronary artery fistulae are thought to arise as a persistence of sinusoidal connections between the lumens of the primitive tubular heart that supply myocardial blood flow in the early embryologic period. Coronary artery fistulae occur in the absence of obstruction. Another explanation may be faulty development of the distal branches of the coronary artery rectiform vascular network.

When these channels persist in association with outflow obstruction (eg, pulmonary atresia), they are a variant form of fistulae termed coronary-sinusoidal connections. Associated syndromes most often associated with coronary-sinusoidal connections include pulmonary atresia or stenosis with an intact ventricular septum. In this setting, epicardial coronary blood may flow to and fro during the cardiac cycle.

In systole, right ventricular flow decompresses via coronary-sinusoidal connections to the aorta in a reverse direction, while in diastole, the aorta perfuses the coronary artery in a normal antegrade fashion. This contrasts with coronary arteriovenous fistulae in the absence of outflow obstruction, in which coronary steal is the primary pathophysiologic problem. In pulmonary atresia and coronary-sinusoidal connections, myocardial ischemia, necrosis, fibrosis, and systemic desaturation may occur. Areas of coronary stenosis and/or interruption of the coronary system may complicate this abnormality. No associated noncardiac conditions are observed.

Frequency

United States

Coronary artery fistula accounts for 0.2-0.4% of congenital cardiac anomalies. Approximately 50% of pediatric coronary vasculature anomalies are coronary artery fistulae.

Mortality/Morbidity

Fistula-related complications are present in 11% of patients younger than 20 years and in 35% of patients older than 20 years. Larger fistulae progressively enlarge over time, and complications, such as congestive heart failure, myocardial infarction, arrhythmias, infectious endocarditis, aneurysm formation, rupture, and death, are more likely to arise in older patients. Spontaneous closure has been rarely reported.

The mortality rate related to surgical repair of coronary artery fistula typically ranges from 0-4%. Variations that may increase surgical risk include the presence of giant aneurysms and a right coronary artery–to–left ventricle fistula. Complications of surgery include myocardial ischemia and/or infarction (reported in 3% of patients) and coronary artery fistula recurrence (4% of patients).

Race

No race predilection is noted.

Sex

No sex predilection is noted.

Age

Coronary artery fistula may present in patients at any age but is usually suspected early in childhood when a murmur is detected in an asymptomatic child. Older children with murmurs may present with symptoms of coronary insufficiency. In a multicenter review, appreciably more problems related to operative risks and postoperative complications occurred after age 20 years.⁴

Clinical

History

Most children with coronary artery fistulae (CAF) are asymptomatic, and continuous murmur may be audible on routine examinations. In older patients, symptoms may include the following:

• Dyspnea on exertion
• Angina
• Fatigue
• Palpitations
• Patients with large fistulae may present with high-output congestive heart failure, although rarely.

Physical

• Most patients are asymptomatic, and coronary artery fistula is suspected following detection of a continuous murmur on routine examination.
• Upon clinical examination, the murmur is suggestive of patent ductus arteriosus but is heard lower on the sternal border than usual; thus, the location often is atypical for a patent ductus arteriosus. In addition, the murmur may have an unusual diastolic accentuation, and the continuous murmur of a coronary artery fistula often peaks in mid-to-late diastole, which is uncharacteristic of the systolic accentuation in a patient with patent ductus arteriosus.
• If the fistula connects to the left ventricle, only an early diastolic murmur may be heard, as little coronary flow is evident during the period of systole.
• Some patients with fistulae with a large shunt may present with signs of congestive heart failure and angina.

Causes

• Most coronary artery fistulae are congenital and may be found in patients with structurally normal hearts. A specific variant form of coronary artery fistula (coronary-sinusoidal connection) that occur in association with congenital heart disease arise most often in association with severe right or left ventricular outflow obstruction, such as pulmonary atresia with intact ventricular septum or aortic atresia with hypoplastic left heart syndrome. In outflow obstructions, the fistula serve to decompresses the ventricle in a retrograde flow fashion.
• Rarely, acquired forms of coronary artery fistula may occur as a result of septal myectomy in association with hypertrophic cardiomyopathy, muscle bundle resection in operative repair of tetralogy of Fallot, as a complication of radiofrequency ablation of accessory pathways, penetrating or nonpenetrating trauma, endomyocardial biopsy, permanent pacemaker implantation, or as a complication of coronary arterial procedures.

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