Coronary Artery Fistula

Abnormal communication between a coronary artery and a cardiac chamber (coronary cameral fistula) or a great vessel (pulmonary artery, coronary sinus, superior vena cava, pulmonary vein). Found in about 0.1 to 0.2% of angiograms and accounts for about half of coronary anomalies of clinical importance.

• Origin: right coronary artery about 50%, left anterior descending about 40 to 45%. Drainage: right ventricle about 40%, right atrium about 25%, pulmonary artery about 17%, then coronary sinus, left atrium, left ventricle and superior vena cava (drainage to the right heart in about 90%).
• Most are congenital. Acquired fistulae follow cardiac surgery, trauma, endomyocardial biopsy, percutaneous coronary intervention, pacemaker lead placement or chest wall injury.
• Mechanism: a left to right shunt into a low pressure chamber, volume overload of the receiving side, and coronary steal (blood diverted from myocardium beyond the fistula) causing ischaemia. The feeding artery dilates progressively and becomes tortuous or aneurysmal.
• Most small fistulae are asymptomatic throughout life. With age, complications accumulate: heart failure, atrial arrhythmia, ischaemia, thrombosis, aneurysm and rupture, and infective endarteritis or endocarditis (about 3 to 5%). Spontaneous closure is uncommon (about 1 to 2%).

• Asymptomatic with a continuous murmur, loudest in diastole, at the lower sternal edge or the site of drainage, in most children and young adults.
• Symptoms in adults: exertional dyspnoea, fatigue, angina (steal), palpitations, and signs of heart failure with a large shunt. Pulmonary hypertension is uncommon.
• Differential diagnosis: patent ductus arteriosus, ruptured sinus of Valsalva aneurysm, aortopulmonary window, aortic regurgitation with ventricular septal defect, venous hum, systemic arteriovenous malformation, anomalous origin of the left coronary artery from the pulmonary artery (infants), and coronary pulmonary microfistulae in hypertrophic cardiomyopathy.
• Complications: heart failure, myocardial ischaemia and infarction, arrhythmia (atrial fibrillation), thrombosis of an aneurysmal fistula with embolism, rupture with tamponade, pulmonary hypertension, and infective endocarditis.

• ECG: often normal; ischaemic change, left ventricular hypertrophy, or atrial fibrillation. Chest X-ray: normal or cardiomegaly with increased pulmonary flow.
• Transthoracic echocardiography with colour Doppler: dilated feeding coronary artery, continuous flow at the drainage site, chamber enlargement.
• CT coronary angiography is the best test for origin, course, size, aneurysm and drainage site, and is used for planning closure. Cardiac MRI quantifies the shunt (Qp:Qs). Invasive angiography defines the feeding branches and the anatomy needed for device closure.
• Functional testing for ischaemia when symptomatic. Shunt is significant at Qp:Qs of 1.5 or more.
• Blood cultures when febrile with a new change in the murmur.

• Small asymptomatic fistula (no chamber enlargement, Qp:Qs less than 1.5): observe with echocardiography every 3 to 5 years.
• Closure indications: symptoms (angina, heart failure, arrhythmia), significant shunt (Qp:Qs 1.5 or more) or ventricular volume overload, ischaemia, aneurysm or thrombus, previous endocarditis, or a large fistula in a young patient.
• Techniques:
  • Transcatheter closure with coils, vascular plugs or covered stents, suitable for a single narrow drainage site with no large side branches arising proximal to the intended closure site. Success is about 90% or more, mortality 1% or less, and complications include residual shunt, coil embolisation, thrombosis, and myocardial infarction from branch occlusion (about 4%).
  • Surgical ligation with or without cardiopulmonary bypass for complex, multiple, large or aneurysmal fistulae, and bypass grafting when closure would endanger myocardium.
• After closure: aspirin 75 to 100 mg daily for 6 months (add clopidogrel 75 mg daily for 1 to 3 months if a stent was placed); echocardiography or CT at 1 to 6 months to confirm closure.
• Medical therapy for symptoms before closure:
  • Heart failure: furosemide 20 to 40 mg daily and ramipril 2.5 mg daily titrated to 10 mg.
  • Angina: bisoprolol 2.5 to 10 mg daily; nitrates carefully (they can worsen steal).
  • Atrial fibrillation: rate control with bisoprolol, anticoagulation with warfarin to INR 2.0 to 3.0 or apixaban 5 mg twice daily (2.5 mg twice daily if two of age 80 or more, weight 60 kg or less, creatinine 133 micromol/L or more).
  • Infective endocarditis: blood cultures first, then IV antibiotics chosen by the organism for 4 to 6 weeks.
• Endocarditis prophylaxis is needed only after closure with prosthetic material for 6 months, or after previous endocarditis: amoxicillin 2 g orally (50 mg/kg in children) 30 to 60 minutes before dental procedures; azithromycin or clarithromycin 500 mg (15 mg/kg in children) if allergic to penicillin (clindamycin is no longer recommended).
• Special groups:
  • Pregnancy: small fistulae are tolerated; large shunts raise the risk of heart failure and arrhythmia, so close before pregnancy.
  • Children: observe small fistulae; close significant shunts at 2 to 4 years or earlier if heart failure develops.
  • Elderly: complications increase with age; close if symptomatic or aneurysmal, balancing procedural risk.
• Red flags: chest pain with ST change, syncope, new heart failure, fever with a changing murmur, sudden chest pain with hypotension (rupture).
• Follow up: yearly review with echocardiography for large fistulae; after closure at 1 month, 6 months and 12 months, then every 2 to 3 years, with CT or angiography if symptoms recur.