Ectatic left circumflex artery with fistula to coronary sinus presenting with inferior wall myocardial infarction

Abstract

Coronary arteriovenous fistulae are a rare but potentially curable cause of ischaemic heart disease and should be considered as a differential diagnosis especially in patients lacking classical risk factors for coronary artery disease. We discuss one such case of cardiac ischaemia resulting from a coronary arteriovenous fistula. While there are sporadic case reports of similar patients in medical literature, our patient is the first reported case of ST-elevation myocardial infarction secondary to the fistulous connection.

Background

Coronary artery fistulae are an uncommon congenital anomaly, seen in 0.1–0.2% of all coronary angiograms.¹ The majority of these fistulae are entirely asymptomatic, and are incidentally detected in angiograms ordered for other indications. Occasionally, patients may present with symptoms ranging from exertional dyspnoea and chest pain to complications such as infective endocarditis and congestive heart failure.

Case presentation

A 60-year-old man with no pre-existing illness presented with crushing central chest pain since the past 6 h, occurring at rest and associated with profuse sweating. He denied any associated breathlessness. He also denied any history of substance abuse. General physical examination revealed stable vital signs including pulse rate and blood pressure. Cardiovascular examination was essentially normal. Clinical signs of cardiac failure including peripheral oedema, basal crepitation and third heart sounds were absent. Jugular venous pressure was normal with preservation of all waveforms.

Investigations

Emergent electrocardiography demonstrated evolved inferior wall myocardial infarction. Transthoracic echocardiography showed infero-posterolateral wall hypokinesia. Left ventricular systolic function was maintained with an ejection fraction of 55%. Preliminary laboratory investigations revealed no evidence of renal or hepatic dysfunction.

Coronary angiography was performed. A co-dominant diffusely ectatic left circumflex artery was notable. A large fistula was seen communicating between the distal circumflex artery and the coronary sinus (figure 1, Video 1). The left main coronary artery was also ectatic. Just prior to draining of fistula into the coronary sinus a discrete stenosis was noted (Video 1). The remainder of the epicardial coronary artery morphology was normal. Contrast-enhanced 64-slice multidetector CT with volume rendered three-dimensional reconstruction was confirmatory, delineating a dilated circumflex artery with a distal fistulous communication to the coronary sinus (figures 2 and 3).

Figure 1.

Coronary angiogram in the antero-posterior-cranial view demonstrating the left anterior descending artery and the large left circumflex in the left atrio-ventricular groove (arrows). LAD,  left anterior descending artery.

Figure 2.

CT with volume rendered three-dimensional reconstruction of the left coronary artery illustrating the relation between LAD and LCX. LAD, left anterior descending artery; LCX, left circumflex artery.

Figure 3.

CT with volume rendered three-dimensional reconstruction of the left coronary artery illustrating the subsequent course of the fistula into the coronary sinus. LAD, left anterior descending artery; LCX, left circumflex artery.

Video 1

Coronary angiography in the antero-posterior-cranial view demonstrating the dilated left circumflex artery and the course of the fistula in the atrio-ventricular groove. The fistula has a discrete stenosis at its distal end just before its entry into the coronary sinus.

Treatment, outcome and follow-up

The patient was advised ligation of the fistula/transcatheter embolisation with systemic anticoagulation, but refused on financial grounds. He was subsequently discharged on dual therapy with aspirin and clopidogrel, and atorvastatin.

Discussion

Coronary arteriovenous fistulae can involve any of the major epicardial arteries, and terminate either in the coronary sinus, or directly in the right atrium. Functionally, this results in a left-to-right shunt, overloading the left ventricle, and eventually progressing to congestive heart failure. Of the various possible configurations, the commonest seen is a connection between the right coronary artery and the coronary sinus.² Fistulae of the left circumflex artery are relatively rare, and are restricted principally to sporadic case reports.

Although coronary angiography remains the golden standard for diagnosis of coronary arterio-venous fistulae, newer non-invasive modalities such as multislice computed tomographic imaging³ and MRI can be used to delineate coronary anatomy and plan appropriate intervention. Transthoracic echocardiography has also been used to diagnose the condition.⁴

The great majority of coronary fistulae are congenital in nature. Acquired causes of such fistulae include penetrating chest injuries, and cardiovascular procedures such as coronary bypass surgery and mitral valve replacement. In our own case, the absence of a relevant history indicates congenital malformation as the likely aetiology.

Although frequently asymptomatic, coronary arteriovenous fistulae can present with symptoms such as exertional dyspnoea or angina.⁵ These manifestations are the result of a ‘coronary-steal’-like phenomenon,⁶ wherein left-to-right shunting from the coronary arterial system to the low-pressure coronary sinus diverts blood away from the myocardium producing ischaemic sequelae, mimicking coronary atherosclerotic disease.⁷ Myocardial infarction attributable to this cause is yet to be reported in the medical literature.

Regardless of symptomatology, anatomic closure should be performed if the fistula is haemodynamically significant, in order to prevent long-term complications⁸ such as congestive cardiac failure and infective endocarditis. Indeed, some authors suggest closure in all patients with asymptomatic fistulae.⁹ This can be accomplished either by open surgical ligation^{2 10} or by trans-catheter technique utilising microcoils or embolisation.

To the best of the authors’ knowledge, this is the first ever reported case of myocardial infarction secondary to coronary arterio-venous fistula. The absence of epicardial artery stenosis on coronary angiography, as well as the anatomical correspondence between the area of myocardium involved and the left circumflex artery clearly implicate the fistula as the culprit lesion.

Learning points.

• Coronary arteriovenous fistulae are a potential, albeit rare cause of myocardial infarction.

• Coronary angiography or an acceptable alternate form of coronary imaging should be performed in all patients, especially those lacking classical risk factors for ischaemic heart disease, to rule out this correctable condition.