Case Presentation: A 62-year-old male with no significant medical history presented to our clinic after new diagnosis of atrial fibrillation. He had no associated symptoms and endorsed great exercise tolerance. Transthoracic echocardiogram (TTE) was ordered and he was started on metoprolol 25 milligram two times daily. TTE demonstrated normal global systolic function with severely dilated right and left atrium. It also demonstrated ectatic left main coronary artery (LMCA) with multiple dilated coronaries along the basal and inferolateral portion of left atrium. Cardiac computed tomographic angiography (CTA) revealed dilated LMCA arising from the posterior aspect of coronary sinus, with separate origin of the left anterior descending (LAD) and left circumflex arteries from the dilated LMCA (Figure 1). Subsequently, cardiac catheterization confirmed serpiginous and aneurysmal coronary arteriovenous fistula (CAVF) communicating dilated LMCA with coronary sinus, measuring 1.5 centimeter with Qp:QS ratio of 1.8. Patient was referred to cardiothoracic surgery for further evaluation.

Discussion: CAVF is a rare congenital heart disease, which accounts for 0.04% of all cardiac malformations. [1,2] It is characterized by abnormal conduit between the coronary arterial and venous circulation. [2] In majority of cases, it involves right coronary artery or LAD artery. Our case is unique such that the origrin of CAVF was LMCA, which is reported in less than 5% of cases. [3] Most patients with CAVF are asymptomatic but it can present with angina pectoris from myocardial ischemia due to coronary steal syndrome, exertional dyspnea, orthopnea or extremity swelling from right ventricular overload from left to right shunting. [2] It has also been associated with paroxysmal atrial fibrillation, ventricular arrythmias and sudden cardiac death particulary in young athletes. [2,4] The prevalence is 0.002% in the general population. [5] It should be suspected in patients with unexplained heart failure or in patients with history of chest trauma, irradiation, myocardial infarction or cardiac procedures. [2] Coronary angiography is the primary diagnostic and therapeutic modality for assessment of the CAVF but other non-invasive modalities such as multidetector cardiac CTA and magnetic resonance imaging can also provide detailed information regarding the anatomy including origin, patency and termination of CAVF. [2,6]

Conclusions: American College of Cardiology (ACC) and American Heart Association (AHA) recommend monitoring small asymptomatic fistulas while closing fistulas greater than 250 millimeter irrespective of symptoms and all symptomatic fistulas regardless of the size. [7] Closure can be achieved with percutaneous transcatheter approach or surgically with sternotomy. Patient’s with proximal, non-tortuous and easily accessible fistulas are the candidates for occlusion with coils and plugs with angiography. [2,7] Guidelines recommend following small, asymptomatic fistulas every 3-5 years with repeat non-invasive modalities to monitor progression. [2,7]

IMAGE 1: Figure 1