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Most coronary artery fistulae are congenital, arising from incomplete obliteration of the primitive myocardial sinusoids and multiple fistulous tracts. Occasionally these fistulae may result from cardiac interventions such as percutaneous transluminal coronary angioplasty or endomyocardial biopsy. Involvement of the right coronary artery is marginally more common than the left, and drainage into the right atrium or ventricle is the rule, although drainage into the pulmonary artery, left heart, coronary sinus, and superior vena cava have been reported. Normally, the coronary artery feeding the fistula is dilated and runs a tortuous course, giving the serpiginous appearance illustrated in this case.
Patients with congenital coronary artery fistulae may be asymptomatic for many years; however, by middle age they often are symptomatic. Angina is the most common symptom because of coronary steal and coexisting atherosclerosis; however, some patients, as in this case, may present solely with exertional dyspnoea. Classically, a continuous murmur is described, but pansystolic and diastolic murmurs in isolation have been reported.
Although transthoracic echocardiography may be helpful in initial screening, a transoesophageal echocardiogram may be diagnostic and precise in delineating the fistulous vessel origin, course, and drainage. In addition, coexistent congenital cardiac disease, present in up to 20% of cases, can be confirmed or excluded. In the diagnosis of coronary artery fistulae, transoesophageal echocardiography is comparable to angiography, and may be superior.
(Top) Transoesophageal vertical plane image demonstrating the left atrium (LA) and right atrium (RA) with a tortuous left coronary artery fistula (F) draining into the right atrium. (Bottom) Same as above but demonstrating flow from the fistula into the right atrium.