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Their exact incidence is unknown but the defect is rare and usually occurs in isolation.

The majority of these fistulas are congenital in origin although they may occasionally be detected after cardiac surgery. They do not usually cause symptoms or complications in the first two decades of life, especially when small. After this age, the frequency of both symptoms and complications increases. Complications include 'steal' from the adjacent myocardium, thrombosis and embolism, cardiac failure, atrial fibrillation, rupture, endocarditis/endarteritis and arrhythmias. Thrombosis within the fistula is rare but may cause acute myocardial infarction, paroxysmal atrial fibrillation and ventricular arrhythmias. Spontaneous rupture of the aneurysmal fistula causing haemopericardium has also been reported.

Whilst two-dimensional echocardiography helps to differentiate between the different shunts, coronary angiography is the main diagnostic tool for the delineation of the anatomy.

The main differential diagnosis is patent arterial duct, although other congenital arteriovenous shunts need to be excluded.

Surgery was the traditional method of treatment but nowadays catheter closure is recommended using a variety of closure devices, such as coils. With the catheter technique, the results are excellent with infrequent complications.