Single Coronary Artery from Right Aortic Sinus Giving Rise to Left Main Coronary Artery and a Hypoplastic Right Coronary Artery

   ABSTRACT: Coronary artery anomalies are uncommon and the occurrence of a single coronary artery with no structural heart disease is very rare. We report a hitherto undescribed type of single coronary artery originating from the right aortic sinus giving rise to left main coronary artery and right coronary artery that was hypoplastic proximally. J INVASIVE CARDIOL 2010;22:E112–E114    Key words: congenital defects, coronary artery anomalies    Case Report. A 43-year-old male with no coronary risk factors was referred for coronary angiography with three months history of exertional angina and a positive treadmill test. His electrocardiogram and echocardiogram were normal. A selective coronary angiogram demonstrated a single right coronary ostium leading to a common trunk from which the right coronary artery (RCA) originated and was proximally hypoplastic (Figure 1). The elongated left main coronary artery (LMCA) originated from the proximal part of the common trunk coursing intraseptally and then reached the anterior interventricular groove and divided into left anterior descending (LAD) and left circumflex (LCX) arteries (Figures 2A and B). The LMCA and LAD were free of atherosclerotic disease, but the LCX showed an early obtuse marginal with mild ostial stenosis (Figure 3). The LCX coursed backward from the proximal LAD forming the typical “eye” sign. A left ventricular angiogram revealed an ejection fraction of 65% and opacification of the left coronary artery, but no vessel in the usual RCA position (Figure 4). The patient was advised to follow an optimal antianginal medical treatment regimen and was doing well at 1-year follow up.    Discussion. Coronary artery anomalies are rare and represent about 1.3% of coronary angiograms.¹ They are usually asymptomatic. Various classifications are described in the literature and the common anomalies are: an anomalous circumflex artery originating from a separate ostium in the right sinus of Valsalva or as a proximal branch of the RCA; a RCA arising from the left sinus of Valsalva or as a branch of a single coronary artery; a left coronary artery or LAD originating from the right sinus of Valsalva or as a branch from a single coronary artery. The last two types can have an interarterial course and are associated with sudden cardiac death.²    A single coronary artery (SCA) with no structural heart disease is a rare congenital anomaly of the coronary arteries where only one coronary artery arises from the aortic trunk by a single coronary ostium, supplying the entire heart. The prevalence of SCA is reported to be less than 3% of all major coronary anomalies.¹ Incidence of an isolated single coronary artery is reported in about 0.024–0.04% of the population.³ The frequency of SCA arising from the right or left sinus of Valsalva is similar, though a right-sided origin presents with slightly higher frequency.^4,5 The anomaly of SCA may be associated with chest pain, sudden death, cardiomyopathy, syncope, ventricular fibrillation, or myocardial infarction.^1–3    In single coronary arteries arising from the right aortic sinus, the LMCA often arises from the proximal part of the common trunk and courses towards the anterior inter-ventricular groove where it divides. The anomalous LMCA arising from the right coronary system can follow any of the four courses (septal, anterior free wall, retro-aortic and interarterial).^5,6 The interarterial course commonly occurs where the vessel passes between the great vessels (aortic root and the pulmonary trunk), and is reported to present with sudden cardiac death in more than a third of patients.⁷ In patients with coronary anomalies, various causes for ischemia other than atherosclerosis have been described in the literature including slit-like ostium, ostial ridge, tangential origin of anomalous artery, coronary spasm, and interarterial or intramural course (at the aortic wall)8 with compression or exercise-related narrowing. In our patient, the LMCA traversed intraseptally towards anterior interventricular groove to divide into LAD and LCX. The angiographic appearance of the typical “eye” formed by the downward loop of LMCA and upward loop of LCX in our patient indicated a septal course of the LMCA.⁵ This type is usually considered benign in the absence of coronary stenosis.    The rarity in the angiogram is that the RCA was hypoplastic. This combination of hypoplastic proximal RCA in association with this type of SCA has not been described previously. Hypoplastic coronary artery disease (HCAD) occurs rarely and refers to the underdevelopment of one or more major coronary arteries or its major branches. Most of the patients reported were young adults and experienced sudden cardiac death without antecedent symptoms. Diagnosis is often made at autopsy.⁹ HCAD was first reported in 1970 by Ogden et al who found an incidence of 0.022% in a study of 224 necropsy cases of congenital artery anomalies.¹⁰ In living patients the diagnosis is made by coronary angiography.¹¹ There are few reports of SCA with LAD agenesis or hypoplasia.^12,13 Our patient is a combination of rare coronary anomalies wherein there was an SCA with hypoplastic proximal RCA. While the intraseptal course of LMCA was a benign coronary anomaly in our patient, insufficient perfusion due to hypoplastic RCA can cause apparent myocardial ischemia. Angiographically, there was adequate perfusion from the “dominant” looking LCX. This has been noted in a previous report, wherein, a nuclear scan documented evidence of persistent myocardial ischemia in a patient with distal HCAD despite no clinical symptoms.¹¹ Moreover, recognition of this kind of anomaly is very important because an ostial occlusion of either the common trunk or ostial LMCA can cause severe coronary insufficiency, since a large area of myocardial perfusion is jeopardized.¹⁴    The imaging modalities for the delineation of coronary anomalies include widely available standard coronary angiography, which is a sufficient method of evaluation in most of the patients. Echocardiography, multi-slice computer tomography or magnetic resonance imaging are also being widely used.7,15 Symptomatic patients with SCA are advised to seek medical treatment or intervention (percutaneous coronary intervention or coronary artery bypass surgery) in the presence of coronary stenosis. Surgical correction, either by coronary reimplantation or unroofing of intramural coronary segment, is usually recommended for those anomalies taking an interarterial course.    In conclusion, we report an undescribed type of single coronary artery originating from the right aortic sinus in which the left main coronary artery arises from the common trunk and the right coronary artery was hypoplastic.

References

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_________________________________________________ From the Department of Cardiology, Royal Hospital, Sultanate of Oman, Muscat. The authors report no financial relationships or conflicts of interest regarding the content herein. Manuacript submitted Septebmer 30, 2009, provisional acceptance given November 3, 2009, final version accepted December 4, 2009. Address for correspondence: Prashanth Panduranga, MD, MRCP, Department of Cardiology, Royal Hospital, PB 1331, Sultanate of Oman, Muscat, 111. E-mail : prashanthp_69@yahoo.co.in