Left circumflex coronary arteriovenous fistula presenting as acute coronary syndrome

Summary

Coronary arteriovenous fistula (CAVF) is a rare congenital anomaly that is seen in 0.1–0.2% of coronary angiograms. A 79-year-old man with no risk factors for coronary artery disease, presented with unstable angina and normal clinical examination. Coronary angiogram revealed a large left circumflex coronary artery with multiple aneurysms exiting into right atrium. Although coil embolization was feasible, he was managed conservatively as he responded to medications. This case shows that large CAVF can be asymptomatic up to the 7th decade of life, manifest as acute coronary syndrome, can present without any murmur on auscultation, and medical management can be effective.

Introduction

A congenital coronary arteriovenous fistula (CAVF) is a direct communicating channel between a coronary artery and the right atrium (RA) or ventricle, the coronary sinus, or the vena cava. They are uncommon and are seen in only 0.1–0.2% of coronary angiograms [1]. Even rarer is a left circumflex (LCX) coronary arteriovenous fistula with multiple aneurysms, exiting into the RA and presenting as acute coronary syndrome (ACS).

Case report

A 79-year-old man with no risk factors for coronary artery disease presented with new onset typical anginal type of chest pain, lasting for 5–10 min, which was progressively increasing in intensity, and duration for 15 days. On admission he had angina at rest but was hemodynamically stable. On auscultation first and second heart sounds were heard but there were no added sounds or murmur. His electrocardiogram showed ST elevation of 0.5 mm in inferior leads but did not show any dynamic change on serial tracings (Fig. 1). His troponin T was negative and other baseline blood investigations including lipid profile were within normal limits. As he had a thick chest wall, 2D echocardiographic window was poor and did not contribute further to his diagnosis. He was diagnosed to have ACS, Braunwald class III B unstable angina [2]. He was started on injection heparin, dual antiplatelet agent, antianginal drugs, and statin and his symptoms improved. Angiography (Fig. 2A–D) revealed a giant, serpentinous LCX with multiple aneurysms interrupted by narrow points exiting into RA. While the proximal part of the fistula gave raise to an obtuse marginal branch which supplied a significant area of myocardium, the rest of the fistula was free of any branches. The left anterior descending artery had insignificant atherosclerotic coronary artery disease and right coronary artery was normal. As there was a narrow point in the fistula distal to origin of obtuse marginal branch, coil occlusion was a feasible option. Since he was pain free following initiation of medications, he opted for medical management and coil closure was not done. He is asymptomatic at 1 year follow-up.

Figure 1.

Electrocardiogram showing 0.5 mm ST elevation in inferior leads.

Figure 2.

(A) RAO view shows a large circumflex coronary arteriovenous fistula. (B) RAO Caudal view shows the obtuse marginal artery arising from the proximal portion of the fistula. Distal to this branch is a narrow segment followed by aneurysmal enlargement. The borderline lesion in proximal left anterior descending artery is also seen. (C) LAO Caudal view shows the distal part of the fistula with multiple aneurysmal swelling interrupted by narrow segments. (D) Lateral view demonstrating the exit point of the fistula into right atrium.

Discussion

CAVFs are uncommon congenital anomalies which may present as ACS. While the majority of these fistulas originate in the right coronary artery and terminate in right ventricle 1, 3, those arising from LCX and exiting in RA are extremely rare. Coronary anomalies should be thought of when ACS patients lack traditional risk factors for coronary artery disease.

Clinically, patients may be asymptomatic or present with palpitations or symptoms of angina. The mechanism of angina includes a “coronary steal” phenomenon [4], thrombosis within the aneurysm leading to local occlusion or distal embolization [5], vasospasm, or associated atherosclerotic coronary artery disease. In our patient, any of the above mentioned factors, combined with age related diastolic stiffness of ventricle with increased wall stress, leading to increased oxygen demand could have precipitated ACS. Other potential complications of CAVF include acute myocardial infarction [6], bacterial endarteritis [7], rupture of fistula [8], and heart failure [9]. A continuous murmur is an auscultatory hallmark of coronary arterial fistula. The precordial location of the murmur is determined by the drainage site of the fistula and not on the artery of origin [7]. When RA is the exit point, continuous murmur is characteristically heard over the right upper or lower sternal border or over the sternum. The systolic component of the murmur is louder because the pressure gradients between aortic root and RA are larger during systole. These findings are valuable, but may not be present in all patients. The thick chest wall coupled with emphysema could have contributed to the absence of the murmur in our case.

Transthoracic echocardiography is an invaluable tool to diagnose and assess CAVF, but a poor echo window may be a limiting factor as seen in this case. Another option is transesophageal echocardiography (TEE), which is superior to transthoracic echocardiography in delineating the characteristics of the fistula [10]. As the fistula was delineated completely by coronary angiography, TEE was not done in our patient.

Treatment options include medical management or closure of fistula either by catheter-based technique or surgery. Medical therapy should include optimal doses of heparin, aspirin, and clopidogrel, as thrombus formation could have precipitated ACS. Although the mechanism of angina in CAVF is “coronary steel phenomenon”, other factors such as vasospasm could have contributed to it. Hence nitrate therapy was initiated to counteract this. Atorvastatin was started to improve the endothelial function and thereby reduce the propensity for angina.

The indications for closure of fistula by intervention or surgery are highlighted in Table 1 [11]. The results of transcatheter closure are similar to surgical outcomes in terms of early effectiveness, morbidity, and mortality [12]. As this patient had a narrow segment in the fistula distal to the origin of obtuse marginal branch, coil occlusion was feasible. VortX coils (Boston Scientific, Natik, MA, USA) are available in various sizes, have improved fluoroscopic visibility and dense fiber placement that promotes thrombosis and complete vascular occlusion. These coils are particularly useful for closure of CAVFs [13].

Table 1.

Indications for closure of coronary arteriovenous fistula.

1.	Symptoms of myocardial ischemia
2.	Positive treadmill test
3.	Perfusion defect on stress myocardial perfusion imaging
4.	Aneurysmal dilation
5.	Mural thrombus
6.	Shunt > 1.5:1

Hence he was advised to undergo stress myocardial perfusion imaging and transcatheter closure of fistula if inducible ischemia is demonstrated in circumflex territory. In view of his age and good response to initial medical therapy, he opted for medical management and coil closure was not done. He continues to be asymptomatic at 1-year follow up. This demonstrates that medical therapy can be an effective treatment option for elderly patients presenting with ACS due to CAVF.

Conclusion

Large left circumflex CAVF can be asymptomatic up to the 7th decade of life, manifest as ACS, and can be present without any murmur on auscultation. Medical management can be effective and should be offered as the first line of therapy in elderly patients.