A rare case of a unique single ostium coronary artery from the right coronary sinus with anomalous left circumflex course

¹Cardiology Department, Ibn Rochd University Hospital, Casablanca, Morocco

^&Corresponding author
Zakaria Qechchar, Cardiology Department, Ibn Rochd University Hospital, Casablanca, Morocco

Introduction    

The incidence of coronary artery anomalies discovered in the largest reported coronary angiography series is about 1.3% [1]. Among these anomalies, the single coronary artery (SCA) in which one coronary artery emerges from a single coronary ostium in the aorta, is a very rare angiographic finding (0.02% to 0.06%) [2] with different subtypes depending on the course of the abnormal artery. A very rare variant of the SCA is the anomalous origin of the left anterior descending artery (LAD) arising from the right coronary artery (RCA). In most cases, this anomaly is incidental finding with no clinical significance; but it can also cause angina, myocardial ischemia and sudden cardiac death, particularly if associated with a proximal course between the aorta and pulmonary trunk, due to the anomalous artery compression between the two vessels during exercise [3]. We present a case of SCA with an ectopic left anterior descending artery (LAD) arising from the proximal part of the RCA, and an anomalous origin of the left circumflex artery (LCx) from the right sinus of Valsalva (RSV).

Patient and observation     

We present the case of a 66-year-old Moroccan female with a history of hypertension, diabetes type 2 and hypercholesterolemia who presented with unstable angina. The patient reported complaints of typical effort angina few months prior to presentation, which progressed to become at rest, associated with NYHA II dyspnea. Vital signs were stable. Physical exam was unremarkable. Resting electrocardiogram was normal except for a type I AtrioVentricular block (AVB). Trans-thoracic echocardiography findings were unremarkable with normal left ventricular dimensions and function (LVEF= 60%) and no segmental wall-motion abnormalities, right ventricle parameters and heart valves were also normal. Both high sensitive troponins´ determinations were negative. Diagnostic coronary angiography was performed with multiple unsuccessful attempts for cannulation of the left coronary artery (LCA) by left Judkins. Selective approach (Figure 1) revealed a dominant RCA originating from the RSV. However, it showed a usual coronary artery anomaly: the Left circumflex artery (LCx) also emerged from the RSV and an ectopic LAD arose from the proximal part of the RCA. No significant stenosis was associated. The gated cardiac computed tomography (CT) confirmed these findings and showed a pre-pulmonic, pre-pericardial course of the ectopic LAD and an anomalous retro aortic course of the LCx (Figure 2, Figure 3). No « at risk » Inter-aorto-pulmonary course was detected and no signs of artery compression or obstruction were found at rest. Therefore, prophylactic surgery was not considered. Medical management was sufficient to control clinical signs during hospital course. However, we considered additional diagnostic stress imaging to evaluate the patient. No symptom nor cardiac event were detected in one year follow-up.

Discussion     

Isolated congenital coronary artery anomalies (CAAs) are very rare, with a prevalence ranging from 0.2-1.3% in the literature [1]. They can be classified into anomalies of origin, course and termination [4]. The majority of CAA are considered benign and are often asymptomatic, usually discovered as incidental findings at the time of catheterization. However, some CAA are considered « at risk » and are the second most frequent cause of sudden cardiac death (SCD) among young athletes, in particular CAAs with a course between the aorta and the pulmonary artery that induce ischemia. Among these, one of the rarest anomalies is the isolated single coronary artery (SCA), that was first described in 1903 and accounts for 0.02% to 0.06% [1,2,5] in angiographic series. SCA is defined by a single isolated coronary artery coming from a single coronary ostium in the aortic root, responsible for the perfusion of the entire heart myocardium [6]. This single coronary can originate either from the Left or the Right Sinus of Valsalva (RSV). SCA anomaly is rarely isolated and usually coexist with other congenital heart diseases such as transposition of the great vessels, bicuspid aortic valve, tetralogy of Fallot, truncus arteriosus, ventricular septal defect, patent ductus arteriosus, coronary arteriovenous fistula and patent foramen ovale [7]. In our patient, no other congenital cardiac defects was associated to the coronary anomaly. The various patterns of SCA are difficult to apprehend, some authors tried to make classifications to better understand this rare anomaly. For example, in 1950, Smith described 3 different types of SCA [6], completed by Ogden and Goodyer´s classification in 1976 [8]. Finally, in 1979, Lipton et al. proposed a more complete classification for isolated SCA that was more practical for angiographers [9]. The anomalous coronary artery is first called “R” (Right) or “L” (Left) depending on the sinus it is emerging from. It is then designated as group I, II, or III. Finally, the letters “A,” “B,” and “P” refer to “anterior,” “between,” and “posterior” patterns, depending on the relationship between the coronary artery and the aorta and pulmonary artery (Figure 4). In our patient´s case, the LCx arose from the RSV separately from the LAD that emerged from the proximal part of the RCA, which can be classified as an isolated single R-III subtype coronary artery anomaly accordingly to Lipton et al. classification. Another classification was Yamanaka and Hobbs´ in 1990 [1], who modified Lipton´s classification by adding “septal” and “combined´´ types, designated as “S” and “C,” in order to describe the anatomical variations with more precision.

The prognosis of SCA is not well defined and depends on the anatomical subtypes. Usually, SCA with left coronary artery (LCA) arising from the RSV, especially with an interarterial course, is classified among the potentially serious anomaly [1,10], responsible of several cases of SCD in young adults during exercise in the autopsy series [10]. Sometimes, the anomaly can affect myocardial perfusion and be responsible of ischemia, heart failure or SCD. SCA group I and III are usually completely benign with an extremely rare incidence of reported SCD unlike group II that is associated with the highest reported SCD [10]. However, cases of angina pectoris and myocardial infarction (MI) have been reported with group III [11], like it was the case of our patient who presented with unstable angina. The mechanism of ischemia in patients without atherosclerosis is not well known, some authors imputate it to the angulation at the origin from the RSV, others to coronary vasospasm or compression of great vessels, particularly in the context of an intense physical exercise. Venturini et al. [12] reported the case of a 74-year-old woman who presented with an acute MI with a SCA arising from RSV with a single ostium bifurcating into left main coronary artery (LMCA) and a dominant RCA. The angiography showed normal coronary arteries, with no significant stenosis. This case resembles ours because of both patients´ advanced age and the combination of a benign course of SCA with acute MI without coronary atherosclerotic lesions. As far as the diagnosis is concerned, the gold standard for the diagnosis and classification of CAA remains coronary angiography. However, exact course determination and relationships can sometimes be difficult to assess. The use of cardiac CT scan can be helpful to visualize the course of the coronary artery in a three-dimensional image, can characterize plaques and assess intraluminal narrowing with high accuracy [13]. Furthermore, coronary CT scan has an excellent spatial resolution to describe the relationship of the anomalous arteries with the great vessels cardiac chambers [14]. Other imaging modalities include cardiac magnetic resonance imaging (MRI) that is a suitable alternative to CT despite its lower spatial resolution, and transesophageal echocardiography (TEE) [15]. All in all, coronary angiography and imaging modalities are complementary when the diagnosis and therapeutic approach are not clearly established by cardiac catheterization. In fact, the course of the anomalous coronary artery and its relation to the great vessels was unknown in more than two third of cases in a Spanish angiographic serie including 23 300 coronary angiographies, which was imputable to the rare use to imaging techniques (only 2 cases, by TEE and MRI) [16]. In our case, we diagnosed the SCA anomaly by cardiac angiography and used coronary CT angiography to determine its course and its relationship with the great vessels. The patient had a pre-pulmonic, pre-pericardial course and an anomalous retro aortic course of the LCx. Therapeutic modalities are individualized depending on the patient's age, ischemic symptoms and the associated coronary lesions. Patients of more than 50 years have a very low incidence of SCD, hence, the therapeutic approach is similar to normal population with ischemic heart disease. In younger patients with a potential malignant variant, the risk SCD is greater and surgery is the treatment of choice [17]. Our patient had advanced age and her anatomic variation was considered benign, therefore, surgical intervention was not offered and she was managed with conservative medical therapy and regular follow-up.

Conclusion     

Left coronary artery emerging from the right sinus of Valsalva is a rare form of single coronary artery anomaly that can be responsible of ischemia sudden cardiac death. If the anomalous artery course is not between the great vessels, this anomaly is considered as relatively benign. Coronary CT scan and coronary angiography give the diagnostic confirmation. Despite this anomaly´s rarity, increased awareness may enable early diagnosis especially in active young individuals to prevent SCD. Multi-disciplinary management involving cardiologists, interventionists and surgeons, is required to provide individualized treatment strategies based on clinical presentation and coronary anatomy, and in some cases like ours conservative medical approach is preferred.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

All the authors contributed equally in drafting the manuscript. All the authors read and agreed to the final manuscript.

Figures     

Figure 1: left anterior oblique (LAO) angiogram showing single coronary artery emerging from the right coronary sinus

Figure 2 : coronary CT angiography: single coronary artery with prepulmonic left anterior descending artery and retro aortic circumflex artery with anomalous course

Figure 3: 3D CT scan angiography reconstruction presenting single coronary artery with prepulmonic left anterior descending artery and retro aortic circumflex artery with anomalous course

Figure 4: classification of angiographic types of isolated single coronary artery patterns according to Lipton et al. Abbreviations: R = right, L = left, RCA = right coronary artery, LCA = left coronary artery, LAD = left anterior descending coronary artery, LCx = left circumflex coronary artery, Ao = aorta, PA = main pulmonary artery, A = anterior, B = between and P = posterior to the great vessels

References