Anomalous Origin of the Left Coronary Artery from the Right Coronary Artery: A Rare Case of a Single Coronary Artery Originating

It is thought that most coronary artery anomalies are congenital in origin, resulting from varied formation during embryonic development. Although a number of different anomalies may occur, the overall incidence of this abnormality has been reported between 0.3–1.3% of the general population undergoing cardiac catheterization.^1–4 The incidence may be underestimated, as many of the individuals with these anomalies are commonly asymptomatic, thus many of these anomalies go undetected. It is those individuals who experience signs and symptoms of myocardial ischemia whose anomalies are discovered. The importance of these anomalies arises when the origin and course is such that the anomaly leads to or predisposes a patient to the development of myocardial ischemia or sudden cardiac death. The association of these anomalies with sudden cardiac death has almost exclusively been related to those anomalies taking an interarterial course in which the anomalous artery passes between the great vessels (the aortic root and the right ventricular outflow tract (RVOT) or the pulmonary vessels. Because of the nature of these anomalies, it is vital to recognize the anatomic arrangement of these abnormalities at the time of coronary angiography in order to determine the need for further treatment or surgical intervention. Other modalities, including computed tomographic imaging (CT), magnetic resonance imaging (MRI), and transesophageal echocardiography (TEE), have also been employed to delineate coronary artery anatomy.^5-8 We report a case of a 68-year-old man who presented for coronary angiography secondary to symptoms of exertional chest pressure and an exercise stress test suggestive of myocardial ischemia. He was found to have a rare single coronary artery originating from the right sinus of Valsalva and forming the right coronary artery (RCA) which branched into a large right ventricular artery, forming the conduit to supply the left coronary artery (LCA). The implications of this patient’s anomaly, as well as other coronary artery anomalies and their significance and treatment, are discussed. Case Report. A 68-year-old man with a history of hypercholesterolemia managed with lipid therapy was referred to our institution for coronary angiography. The patient had experienced chest pressure and dyspnea on exertion over the previous few months and was referred by his physician to undergo exercise stress testing. The patient underwent myocardial perfusion imaging and exercised for 10 minutes (13 METS), achieving 91% of his maximal target heart rate (152) without developing any cardiac symptoms. His baseline electrocardiogram (ECG) showed normal sinus rhythm with no ST-T segment abnormalities. His exercise ECG at peak exercise showed 1.0 mm downsloping ST-segment depressions seen in leads II, III, aVF, V5 and V6, with no arrhythmias. These changes returned to baseline at 10 minutes into recovery. Perfusion imaging showed no evidence of any significant fixed or reversible perfusion abnormality, with normal wall motion and an ejection fraction of 73%. The patient was referred for coronary angiography to assess for the presence of coronary artery disease. On left heart catheterization, it became evident that the patient had a single coronary artery originating from the right sinus of Valsalva supplying his coronary arterial system. The mid-portion of the coronary artery forms a right ventricular (RV) branch which courses anteriorly and acts as a conduit to supply the left circumflex (LCX) and the left anterior descending artery (LAD). The rest of this artery continues as the RCA after the mid take-off of the RV branch (Figure 1). No stenotic disease of the coronary arteries was discovered and it was recommended that the patient be managed with medical therapy, including continued management of his hyperlipidemia and risk factor modification. Discussion. Congenital coronary artery anomalies are rare occurrences, with an incidence of about 0.3–1.3% of all patients undergoing cardiac catheterization. These anomalies are commonly asymptomatic, but more potentially serious ones may lead to myocardial ischemia, infarction, and/or sudden cardiac death. The specific course and origin of the anomalous vessel are the factors that determine an adverse or benign outcome.^1–4 Yamanaka and Hobbs9 studied 126,595 patients over a 28-year period who underwent coronary angiography and found that 1.3% (1,686) of these patients had a coronary artery anomaly. Other reports cite the incidence as low as 0.3%, but it is likely that since most patients with the less severe anomalies are asymptomatic, they do not come to medical attention. Of the patients in the study with anomalies, the most common abnormality found in 87% (1,461) of the 1,686 patients was an anomaly of the origin and/or distribution of a coronary artery. The remaining 13% (225) had coronary artery fistulae. Most anomalies were benign, did not result in signs or symptoms, and were discovered incidentally at catheterization. In the experience at our institution, from 8/1/95 till 12/30/2003, of the 57,008 cardiac catheterizations performed, 505 (0.01%) patients had an anomaly of their coronary arteries. An anomalous circumflex artery is the most common anatomic variant, and it occurs in approximately 0.32–0.67% of patients who undergo coronary angiography.^7,9 The LCX typically originates from a separate ostium in the right sinus of Valsalva, or as a proximal branch of the RCA, and passes behind the aortic root. In 0.03–0.17% of patients who undergo angiography,^7,9 the right coronary artery arises from the left sinus of Valsalva as a separate vessel or as a branch of a single coronary artery. Yamanaka and Hobbs9 noted that the RCA coursed immediately anteriorly between the aortic root and the RVOT to enter the right atrioventricular groove. This variant can be associated with sudden cardiac death in up to 30% of patients.⁷ The left coronary artery can originate from the right sinus of Valsalva or as a branch from a single coronary artery in 0.09–0.11% of angiographic studies. The interarterial course commonly occurs (up to 75% of patients) where the vessel passes between the great vessels (aortic root and the RVOT), and is associated with sudden cardiac death. The LCA also may travel anterior to the RVOT or posterior to the aortic root, or it may follow a septal course.^7,9,12–16 Garg et al.¹² examined the presence of atherosclerosis in anomalous coronary arteries. They found that in their study population, atherosclerotic plaques were seen in the anomalous arteries of only 13/39 (33.3%) patients, which was much less than the overall incidence of coronary artery disease in patients with congenital coronary anomalies in their series (66.6%). They therefore concluded, based on their substudy, that there does not appear to be an increased risk for the development of atherosclerotic coronary artery disease in anomalous coronary arteries.¹² In our patient, a single coronary artery arose from the right sinus of Valsalva and formed the RCA after an RV branch in the mid-portion which formed the LCA. This abnormality where the LCA arises from either the right sinus of Valsalva or as a branch from a single coronary artery forming the RCA, is extremely rare, occurring in 0.09–0.11% of angiographic studies.⁷ This accounts for 1.2–6.1% of all coronary anomalies.³ The ideal imaging tool for the diagnosis and delineation of coronary artery anomalies is angiography supported by imaging modalities including CT, MRI, and TEE. Although cardiac catheterization remains the gold standard for the evaluation of coronary anatomy, recent studies^6–8,17,18 suggest a complementary role for CT, MRI, and TEE for the diagnosis and delineation of the origin and course of these anomalous coronary arteries. Bunce et al.⁷ describe the use of three-dimensional coronary magnetic resonance angiography to identify the proximal anatomy of anomalous coronary arteries. Dawn et a.^l8 describe the use of multiplane TEE in 32 consecutive adult patients as a complementary tool for the delineation of the proximal course and pattern of flow of anomalous coronary arteries. Sevrukov et al.¹⁸ used contrast enhanced electron beam tomography with three-dimensional reconstruction to visualize the course of an anomalous left coronary artery. Once the diagnosis of the origination and course of the anomalous coronary vessel is made, the question of further management arises. As noted above, the association of these anomalies with sudden cardiac death has almost exclusively been related to those anomalies taking an interarterial course where the anomalous artery passes between the great vessels (the aortic root and the right ventricular outflow tract or the pulmonary vessels). It is these anomalies, when discovered, which are usually recommended to undergo surgical correction. Other anomalies, which include origination of a coronary artery from the pulmonary trunk, are much more severe and usually incompatible with life. They present at birth, and if caught early, may be surgically repaired. Surgical management involves direct re-implantation of the anomalous coronary artery into the proper sinus of Valsalva.^19,20 As the course of our patient’s anomalous LCA took an anterior direction, it was felt that his risk for sudden cardiac death was small, and no further intervention was recommended. Conclusion. We report the case of a 68-year-old man with a history of hyperlipidemia referred for coronary angiography and found to have an anomalous single coronary artery originating from the right sinus of Valsalva, forming the right coronary artery with supply of the left coronary artery from its mid-portion. The interest in this case was sparked by the uniqueness of this anomaly and the implications derived from this and other more serious congenital coronary anomalies. The proper recognition at angiography of these anomalies and their origination and course is the best method for determination of the proper course of action for their management.

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