A Rare Case of a Congenital Single Coronary Artery: Right Coronary Artery Originating From the Distal Left Circumflex Artery

ABSTRACT: A 59-year-old female was admitted to the emergency department with retrosternal pain that began that morning. A resting electrocardiogram showed sinus rhythm without ST-segment abnormalities. In addition, cardiac enzymes (troponin T, CK) were within the normal range. Coronary angiography and contrast-enhanced 320-slice multidetector computed tomography with subsequent 3-dimensional reconstruction revealed the absence of the right coronary artery (RCA) and a left circumflex artery (LCX) supplying the right coronary artery territory. This case describes the extremely rare anomaly of a congenital single coronary artery, with the RCA arising as a terminal extension of the LCX.  

VASCULAR DISEASE MANAGEMENT 2013;10(11):E244-E247 

Key words: anomalies, interventional cardiology, coronary disease, computed tomography,
stress echocardiography

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In October 2012, a 59-year-old female presented to the emergency department with retrosternal pain with radiation to the left arm since the morning. She reported a history of exercise-induced dyspnea and stable angina pectoris for several months. On physical examination, her blood pressure was 126/66 mm Hg and her heart rate was 80 beats per minute. 

A resting electrocardiogram displayed sinus rhythm without any ST-segment abnormalities (Figure 1A). Transthoracic echocardiography demonstrated normal biventricular function (left ventricular ejection fraction by biplane Simpson’s method was 65%) without regional wall motion abnormalities. Mild mitral and tricuspid regurgitation was noted without sign of increased pulmonary artery pressure. Laboratory testing revealed slightly increased C-reactive protein levels (12.8 mg/L) and suppressed TSH (0.06/L) with normal FT3 and FT4 values. 

Cardiac enzymes (troponin T, CK) and other routine biochemistry test values were within the normal range. Past medical history revealed hypertension, hyperlipidemia, and a history of cigarette smoking (50 pack years) as atherosclerotic risk factors. Family history was negative for heart disease. The coronary angiography showed a left anterior descending coronary artery (LAD) arising normally from the left coronary sinus without significant atherosclerotic lesions (Figure 1B, 1C, and 1D). 

The left circumflex artery (LCX) was the dominant vessel with its terminal branch covering the territory of the right coronary artery (RCA) (Figure 1C, 1D). Since we were not able to cannulate the right coronary artery, aortic root angiography was performed to exclude an atypical take-off of the RCA. Aortography (Figure 1B) and contrast-enhanced 320-slice multidetector cardiac computed tomography with subsequent 3-dimensional reconstructions confirmed the absence of the RCA and an LCX supplying the RCA territory (Figure 1E, 1F). Submaximal stress echocardiography did not show signs of exercise-induced myocardial ischemia. Due to the submaximal exercise (maximal workload 75 Watt) and the higher diagnostic accuracy of stress-perfusion cardiac magnetic resonance imaging (MRI), an adenosine stress perfusion cardiac MRI was performed which indicated no evidence of ischemia. In addition, late gadolinium enhancement did not reveal myocardial scars or areas of fibrosis.

Discussion

Congenital coronary anomalies, including anomalous origin, distribution, intercoronary communications, and coronary fistulae are relatively common, occurring at a rate of approximately 1% in the general population.¹ However, a single coronary artery (SCA) is an extremely rare congenital anomaly with an incidence of only 0.024% to 0.066% in the general population.^1-3 Lipton et al² classified the SCA in 9 patterns according to the origin, anatomical course, and termination of the anomalous vessel. The case presented here enters into the L-I pattern, where L implies that the ostium is located in the left sinus of Valsalva. Single coronary artery is commonly associated with other congenital anomalies, such as transposition of the great vessels, coronary arteriovenous fistula, or bicuspid aortic valve.⁴ However, in our depicted case no other associated cardiac anomalies were found and coronary obstructive lesions were absent. Although SCA is generally considered benign, this anomaly has been associated with congestive heart failure, acute myocardial infarction, and sudden cardiac death in the absence of atherosclerosis.^5-7 Thus, Shirani et al⁸ reported that 15% of the patients with SCA had myocardial ischemia as direct consequence of the anomaly. Various mechanisms, including anatomical features such as the compression of the anomalous vessel along its course between the aorta and the pulmonary artery or sporadic spasm of the anomalous coronary artery, have been postulated.

The greatest clinical challenge presented by coronary anomalies is the decision about the treatment. Due to the extremely rare variant of the SCA described in our case, it is difficult to predict whether patients with L-I type SCA are at high risk or will have a benign course. According to an American College of Cardiology/American Heart Association guideline, a surgical revascularization of coronary anomalies with a documented ischemia is recommended.⁹ However, previous studies revealed that standard clinical stress tests often fail to detect myocardial ischemia resulting from coronary anomalies.¹⁰  

Conclusion

We present an extremely rare case of an SCA, with the RCA arising as a terminal extension of the LCX. In our patient’s case, coronary angiography revealed no significant atherosclerotic lesions or abnormally slow angiographic filling to the RCA territory. In addition, stress echocardiography and adenosine stress MRI indicated no evidence of exercise-induced ischemia. Thus, the patient was discharged with beta blocker and ACE inhibitor for the treatment of hypertension and routine cardiac check-ups were recommended once a year. However, physicians must be aware that subjects with SCA are particularly susceptible to deleterious effects of atherosclerotic occlusive disease as the heart and the conduction system entirely depend on the SCA for oxygenated blood supply.

Editor’s Note: Disclosure:  The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no disclosures in relation to the content of this manuscript. 

 Manuscript received May 3, 2013; provisional acceptance given May 22, 2013; manuscript accepted July 17, 2013.   

Address for correspondence: Florian Blaschke, MD, Charite, Universitaetsmedizin Berlin, Campus Virchow-Klinikum, Department of Cardiology, Berlin, Germany. Email: florian.blaschke@charite.de  

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