Rare Coronary Artery Anomaly: Single Coronary Artery from Distal Circumflex Detected by CT

Introduction

A single coronary artery (SCA) is the presence of only 1 coronary trunk arising from the aorta [1]. It is an uncommon congenital anomaly of the coronary arteries distribution, with an incidence of only 0.03% in the general population undergoing coronary angiography [2]. The right coronary artery (RCA) arising from the distal circumflex artery is an extremely rare variety. Single coronary artery is usually asymptomatic [3]. Computed tomography angiography is useful for single coronary artery diagnosis [2].

We report a particularly rare case of a single coronary artery with the right coronary artery (RCA) arising from the distal circumflex artery. This case emphasizes its unusual nature and highlights the importance of non-invasive imaging in the diagnosis of rare cardiovascular pathologies.

Case Report

A 63-year-old man was admitted in our hospital after an inconclusive treadmill stress test attributed to equivocal ECG changes. He had no cardiovascular risk factor or comorbidities. The family history was negative for arrhythmia or sudden cardiac death (SCD). He was initially evaluated for palpitations. Physical examination results were normal. The baseline electrocardiogram and the resting transthoracic echocardiogram were normal. A subsequent Holter monitor assessment showed monomorphic premature ventricular beats less than 50 daily. Because of his low coronary artery disease (CAD) pre-test probability, non-invasive exploration with 64-detector-row multi-slice computed tomography (MSCT) was performed to visualize the coronary arteries. The right coronary artery origin could not be found in the right sinus of Valsalva (Figure 1). The left main coronary artery, left anterior descending (LAD), and circumflex artery (LCX) were normal in origin and distribution. The circumflex coronary artery was clearly predominant, giving off 1 marginal, 2 posterolateral, and the posterior interventricular arteries. However, we discovered the right coronary artery originating from the distal left circumflex artery, following a normal course retrogradely in the right atrioventricular groove. The RCA then gave off a right ventricular branch before terminating its course near the right sinus of Valsalva (Figures 2, 3). The left anterior descending artery (LAD) gave off a diagonal branch to the anterior portion of the right ventricle. There were no significant stenoses in these arterial vessels. No medication was administered. The patient remained asymptomatic, with no complications in follow-up.

Discussion

Normally, the aortic sinuses of the ascending aorta give rise to 2 key coronary arteries – the left coronary artery (LCA) and right coronary artery (RCA). The LCA subdivides into the left anterior descending LAD and left circumflex artery (LCX) [4]. Single coronary artery (SCA) is defined by the presence of only 1 coronary trunk arising from the aorta. It is an uncommon congenital abnormality of the coronary artery [1]. The right coronary artery (RCA) originating from the distal circumflex artery is a very rare variant of single coronary artery. The present case highlights the importance of non-invasive imaging in the diagnosis of rare cardiovascular pathologies like SCA.

The incidence of single coronary artery anomaly is estimated at approximately 0.03%, and around 20 different variations of single coronary artery have been described [2]. Lipton et al introduced the most commonly used classification of SCA [5]. Our case was classified as LI type.

The incidence of the right coronary artery (RCA) emerging from the left coronary system ranges from 0.1% to 0.9% [6,7], with most reported cases showing the RCA originating from the proximal or middle segment of the left anterior descending (LAD). Kim et al reported the case of a 13-year-old girl with the right coronary artery emerging from the left circumflex artery, like our case [7].

In their study, Michalowska et al assessed the prevalence and anatomic characteristics of SCA diagnosed with coronary computed tomography angiography. Between 2008 and 2018, they examined 30 230 patients who underwent coronary CT angiography. Among them, there were 17 cases of SCA. The mean age was 55±19.0 years, with 47% being men. The prevalence of SCA was 0.056%. In 11 cases (65%), the SCA originated from the right sinus of Valsalva. In the remaining 6 cases, it arose from the left sinus of Valsalva [1].

The prevalence described in the tomographic study by Graidis et al was 0.12% (3 of 2572) [8].

SCA is usually asymptomatic. However, the clinical presentation may be variable. Indeed, a patient may present with symptoms such as chest pain, breathlessness, palpitations, fainting, sudden death, ventricular fibrillation, or heart attack, particularly following physical exertion [3]. Some patients experience atypical chest pain or vague symptoms, despite having no evidence of obstructive coronary artery disease and negative stress tests for ischemia [9].

In patients with suspected chronic coronary syndrome and low or moderate (>5–50%) pre-test likelihood of obstructive CAD, coronary computed tomography angiography is recommended to diagnose obstructive CAD and to estimate the risk of major adverse cardiovascular events [10]. It is effective in diagnosing stable coronary artery disease [2] and offers a less invasive option, although it requires use of contrast media [11]. Further evaluation with coronary computed tomography angiography allows for exclusion of other types of congenital coronary anomalies, such as the anomalous origin of the left or right coronary artery from pulmonary artery.

SCA is typically benign; however, certain variants have been linked to a higher risk of sudden cardiac death [12]. In fact, while LI type is considered a benign variant, the other variants, which have a coronary artery branch coursing between the aorta and the pulmonary trunk (RII-III and LII-III types), may predispose to sudden cardiac death.

At present, there is no definitive algorithm for managing patients with SCA. Instead, treatment strategies are tailored to each individual, taking into account the anatomy of their coronary arteries. In patients with significant atherosclerosis and documented ischemia, revascularization is recommended [2]. Our patient was asymptomatic, with no significant stenoses in the arterial vessels. Follow-up was planned.

Conclusions

Single coronary artery (SCA) anomaly is uncommon. The right coronary artery (RCA) originating from the distal circumflex artery is a very rare variant of single coronary artery. Computed tomography angiography (CTA) must be performed in patients with low or moderate pre-test likelihood of obstructive CAD, as it plays a fundamental role in the diagnosis of rare cardiovascular pathologies like SCA.