Correspondence *Mount Sinai Medical Center, 1 Gustave L Levy Place, Box 1030, New York City, NY 10029, USA

Email valentin.fuster@mssm.edu

The case

A 57-year-old man presented with exertional symptoms of dyspnea and presyncope. He had previously been diagnosed with hypertension, hypercholesterolemia and chronic atrial fibrillation, treated in the past with atrioventricular nodal ablation and a permanent pacemaker. The patient denied having chest pain and had no history of coronary artery or pulmonary disease. His cardiac medications included warfarin, atorvastatin, benazepril, and amlodipine. Physical examination revealed a soft (grade II/VI) continuous murmur that could be heard most clearly over the precordium, without clinical evidence of congestive heart failure.

An electrocardiogram revealed atrial fibrillation with ventricular pacing (70 beats/min). Routine laboratory tests were unremarkable. Echocardiography demonstrated some biventricular dilatation with a slight decrease in biventricular function, moderate biatrial enlargement with mild mitral and tricuspid regurgitation, and evidence of mild to moderate pulmonary hypertension with an estimated right ventricular systolic pressure of 40 mmHg. An exercise stress test with echocardiography was performed, and after 4.5 min of the Bruce protocol the patient developed lightheadedness and dyspnea, accompanied by a marked decrease in systolic blood pressure. After multiple episodes of non-sustained polymorphic ventricular tachycardia, the exercise stress test was stopped. Overall, the patient exercised for 4 min 37 s, achieving 7 metabolic equivalent units and 66% of the maximal predicted heart rate. At peak exercise levels, echocardiography revealed notable mid to apical inferior wall hypocontractility, with an abnormal increase in end-systolic volume, consistent with inferior ischemia.

Although coronary angiography showed that the patient had normal left ventricular function and mild mitral regurgitation, without evidence of obstructive coronary artery disease, a large coronary artery fistula was discovered between the right coronary artery and the coronary sinus (Figures 1 and 2). Exertional ischemia and arrhythmia were attributed to coronary steal secondary to the fistula. After discussion with an interventional cardiologist and cardiothoracic surgeon, coil embolization of the coronary fistula was recommended to relieve the patient's symptoms. Embolization was successfully performed with a stainless steel Cook 2.0 coil without residual fistula flow (Figure 3).

Figure 1 An anteroposterior angiographic view of the right coronary artery during contrast injection.

Right atrial and right ventricular wires can be seen on the background. A coronary artery fistula is evident between the distal right posterior descending artery and coronary sinus (arrow). Flow from the fistula into the coronary sinus is also indicated (arrowhead).

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Figure 2 A projection of the anteroposterior angiographic view of the right coronary artery seen in Figure 1 at a different stage of the cardiac cycle, during contrast injection.

Right atrial and right ventricular wires can be seen on the background. The coronary artery fistula is evident between the distal right posterior descending artery and coronary sinus (arrow). Flow from the fistula into the coronary sinus is also indicated (arrowhead).

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Figure 3 An anteroposterior angiographic view of the right coronary artery taken during contrast injection after closure of the fistula using coil embolization.

Right atrial and right ventricular wires can be seen on the background. The arrow indicates where the coil embolized into the coronary artery fistula, between the distal right posterior descending artery and coronary sinus. No contrast filling is evident in the fistula and flow from the fistula to the coronary sinus is absent, indicating successful fistula closure.

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The patient subsequently reported substantial improvements in symptoms and his exercise tolerance also improved. No significant arrhythmias or evidence of residual ischemia were seen during repeat exercise stress echocardiography. At 6-month follow-up the patient remained free from cardiovascular symptoms.

Discussion of diagnosis

Coronary fistulas are congenital or acquired anomalous shunts from a coronary artery to a cardiac chamber or great vessel, bypassing the myocardial circulation. These abnormal connections can lead to a substantial hemodynamic burden, which can affect myocardial perfusion.¹

Coronary fistulas were first described in 1865, but their diagnostic triad was not described until 1978.² Haller and Little characterized these lesions by the presence of an abnormal continuous murmur¹ similar to that of a patent ductus arteriosus (PDA), a left-to-right shunt, and a large coronary artery with evidence of fistula on an angiogram.² They can arise as a result of coronary atherosclerosis, Takayasu's arteritis, or trauma.^{3, 4, 5} Potential complications associated with coronary fistulas include heart failure, myocardial ischemia, infective endocarditis, arrhythmias, and rupture.⁵ Many coronary fistulas, however, are asymptomatic and found incidentally.

Previous population studies using angiography have revealed that the incidence of coronary artery fistula is approximately 0.3%.⁶ Congenital coronary fistulas are the most common type of hemodynamically significant congenital coronary anomaly. A significant congenital coronary anomaly includes origin of the left coronary artery from the pulmonary artery, congenital coronary atresia, and origin of the left coronary artery from the right sinus of Valsalva, with subsequent passage between the great vessels.² In the present case, the patient had no history of vasculitis, coronary artery disease, or trauma, indicating most likely a congenital coronary fistula with delayed presentation during middle age.

Clinical symptoms associated with coronary artery fistulas are variable and largely depend on the magnitude of the left-to-right shunt.³ In a large series of 51 patients with coronary fistulas, angina pectoris occurred in 57% of cases⁷ and was often present in the absence of underlying coronary artery disease. Ischemia is thought to be caused by a phenomenon known as coronary steal, whereby blood flow is shifted away from the distal coronary vascular bed.^{4, 8} Patients can also present with fatigue or dyspnea on exertion, either as an anginal equivalent, or as a manifestation of congestive heart failure. Presence of a large left-to-right shunt from the coronary fistula can lead to pulmonary hypertension and right ventricular failure.^{4, 8} Other potential complications include infective endocarditis, ischemia or infarction-related arrhythmias, and coronary rupture.^{3, 4} The patient described here had a continuous murmur in the precordium, which might have been caused by the coronary fistula. A murmur associated with a coronary fistula and left-to-right flow might become systolic after the development of pulmonary hypertension. It is, therefore, likely that mild pulmonary hypertension in this patient could be attributable to the coronary fistula. Furthermore, the patient presented with exertional dyspnea and arrhythmia, which was most likely a manifestation of coronary steal away from the distal right coronary artery vasculature, resulting in inferior ischemia and ischemic ventricular arrhythmia. Without closure of the fistula, this patient could be at risk of sudden cardiac death.

Although various techniques are available for the diagnosis of coronary fistulas, most are discovered incidentally using coronary angiography. Transesophageal echocardiography can be very useful for noninvasive identification of coronary fistulas, particularly for the identification of their origin, course and drainage site.⁹ Microbubble echo-contrast agents can be used in conjunction with transesophageal echocardiography to enhance visualization.¹⁰ Recently, multidetector CT angiography and MRI have also been used to identify and anatomically define coronary anomalies, including coronary fistulas.^{11, 12} In the patient described here, stress echocardiography revealed ischemia and arrhythmia, prompting us to carry out coronary angiography. Coronary fistula was an unexpected finding in this case, even though these lesions are frequently diagnosed incidentally.

Treatment and management

A variety of approaches can be used to manage coronary artery fistulas. Clinical symptoms of ischemia, such as exertional angina or dyspnea, are the primary indication for closure of a fistula. Indeed, controversy exists regarding the management of fistulas in the absence of associated clinical symptoms.⁴

Although fistulas sometimes close spontaneously, this is a rare occurrence. Surgical vessel ligation was first reported in 1947 and because it demonstrated good long-term safety and efficacy, this technique remained the most frequently chosen treatment option until the first successful percutaneous closure was reported in 1983.^{1, 13, 14} Catheter-based closure methods have since become the preferred treatment option, if technically feasible. This technique can be performed with detachable balloons, stainless steel coils, controlled-release coils, controlled-release PDA coils and the Amplatzer^® PDA occluder (AGA Medical Corporation, Golden Valley, MN).¹⁵ The most frequent complication associated with catheter-based closure is embolization of the occlusion device, and in one study this complication occurred in 7 (17%) out of 40 patients.¹⁵ In the present case, catheter-based closure using controlled-release coil embolization resolved the coronary fistula and the patient's cardiac symptoms. Catheter-based closure has become established as the preferred method of fistula closure in experienced centers.

Conclusion

Here, we describe a patient with a hemodynamically significant coronary artery fistula to the coronary sinus, which was presumed to be a congenital defect and presented as myocardial perfusion and exertional nonsustained ventricular tachycardia. The patient was affected by significant clinical symptoms, which were attributed to the phenomenon of ischemic steal. Following catheter-based coil embolization of the fistula, his symptoms resolved.

Although coronary artery fistulas are rare anomalies, they should always be considered in a diagnostic work-up because they can result in cardiac symptoms and associated complications. With the advent of novel diagnostic techniques such as contrast echocardiography and cardiac MRI, the diagnosis and extent of coronary fistulas can be established more easily. For the management of coronary fistulas, catheter-based closure is a minimally invasive option, associated with a low risk of complications.

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