A rare case of ectopic origin of the left anterior descending artery from the right coronary sinus misdiagnosed as a chronic total occlusion lesion

Abstract

We report a rare case of a left anterior descending artery originating from the right coronary sinus. The original left anterior descending artery was small and appeared occluded; it was initially misdiagnosed as a chronic total occlusion lesion. However, a displaced left anterior descending artery was identified during angiographic evaluation. Although a left main coronary artery arising from the right coronary sinus is uncommon (prevalence of 0.03%), to the best of our knowledge, this is the first reported case of an ectopic left anterior descending artery originating from the right coronary sinus.

Introduction

Coronary artery anomalies, occurring in 0.3%–1.3% of the population, encompass congenital variations in coronary origin, course, and termination. Although commonly incidental, anomalies with an interarterial course pose a significant risk of sudden cardiac death. ¹ An anomalous left anterior descending artery (LAD) originating from the right coronary sinus is exceptionally rare. ² Diagnosis is challenging. Conventional coronary angiography (CAG) may misinterpret anatomy, especially when an anomalous vessel coexists with a suspected chronic total occlusion (CTO), potentially leading to unnecessary intervention. Coronary computed tomography angiography (CCTA) is vital for accurate three-dimensional (3D) anatomical definition. ³

We present a rare case of a man in his early 60s with an initial CAG diagnosis of LAD CTO. Comprehensive evaluation revealed a dual LAD supply, including a hypoplastic native vessel and an ectopic LAD originating from the right coronary sinus, which created the CTO illusion. This is the first reported case of an ectopic LAD originating from the right coronary sinus, and it highlights the critical role of multimodal imaging in diagnosing complex anomalies and preventing misguided revascularization. ⁴

Case presentation

The patient, a man in his early 60s, was hospitalized and received treatment at our hospital in February 2025. He had developed chest tightness 1 month ago in the absence of identifiable predisposing causes, which was unrelated to physical activity, lasted for approximately 30 min, and resolved spontaneously. The patient had a history of coronary heart disease risk factors, including hypertension (5-year history of hypertension managed with 5 mg amlodipine besylate once daily), type 2 diabetes mellitus (2-year history of type 2 diabetes mellitus managed with 1 g metformin hydrochloride extended-release tablets twice daily), smoking, and alcohol consumption. The patient has no family history of coronary heart disease. Biochemical tests revealed the following: fasting blood glucose, 9.9 mmol/L; total cholesterol, 5.01 mmol/L; triglycerides, 1.43 mmol/L; high-density lipoprotein cholesterol, 0.83 mmol/L; and low-density lipoprotein cholesterol, 3.41 mmol/L. Liver and kidney functions were normal. Levels of cardiac biomarkers were as follows: myoglobin, 52.10 ng/mL (normal range: <110 ng/mL); creatine kinase-MB, 0.60 ng/mL (normal range: <5.0 ng/mL); and high-sensitivity troponin I, 33.00 ng/mL (normal range: <53.53 ng/mL). Electrocardiogram findings indicated the following: (a) sinus tachycardia; (b) frequent ventricular premature complexes; (c) complete left bundle branch block (LBBB); (d) ST-T changes (only LBBB); and (e) low voltage in the left precordial leads. Cardiac ultrasonography showed segmental wall motion abnormalities (reduced amplitude of left ventricular lateral wall motion), left ventricular wall thickening, mild dilation of the aortic sinus, mild tricuspid regurgitation, and mild aortic regurgitation. His left ventricular ejection fraction was 57%.

As the patient presented with chest tightness and had multiple risk factors for coronary heart disease, the local hospital performed CAG for further evaluation. CAG showed no stenosis in the left main coronary artery (LMCA), proximal occlusion of the LAD, severe stenosis of the left circumflex artery (LCX), and mild stenosis of the right coronary artery (RCA).

Due to the limitations related to equipment and personnel at the local hospital and considering the patient’s CAG findings, the patient was transferred to our hospital for further percutaneous coronary intervention (PCI). When we implanted a stent in the LCX lesion (Figure 1) and prepared to continue LAD treatment, we noted the absence of distal retrograde flow in the occluded LAD and no visible branches within its territory (Figure 2). We performed bilateral coronary angiography to assess the distribution of blood vessels in this part of the myocardium, which should be supplied by the occluded LAD.

Figure 1.

Stent implantation in the LCX lesion. (a) The mid-segment of the LCX demonstrated severe stenosis. Angle: CAU 30° and (b) stent implanted in the LCX lesion. Angle: CAU 30° LCX: left circumflex artery; CAU: caudal.

Figure 2.

The mid-distal segment of the LAD demonstrates absent blood flow. (a) No visible branches within the territory of the LAD. Angle: CRA 30° and (b) absence of retrograde flow distally in the mid-distal segment of the LAD. Angle: LAO 45° LAD: left anterior descending artery; LAO: left anterior oblique; CRA: cranial.

Remarkably, bilateral coronary angiography showed a looming coronary artery adjacent to the opening of the RCA (right anterior oblique (RAO) 30° + cranial (CRA) 30°). Therefore, we adjusted the angiographic catheter to reach this vascular opening; using angiography, we confirmed that this vessel was the other LAD of the anomalous opening (Figure 3). Its distribution area included the middle and far segment of the LAD, and it supplied blood to the LAD area together with the original LAD (Figure 4). The anomalous LAD demonstrated 20% stenosis in the proximal segment, 50% in the mid-segment, and 70% in the distal segment. We decided to perform conservative management with optimal medical therapy for the anomalous LAD stenosis, as the culprit lesion responsible for the present event was located in the circumflex artery and had been successfully treated using PCI. Therefore, the patient was considered to be diagnosed with the following: (a) unstable angina (acute coronary syndrome (ACS)); (b) hypertension; and (c) type 2 diabetes mellitus. At the 1-month follow-up, the patient was in good condition without any specific discomfort.

Figure 3.

Bilateral angiography incidentally demonstrated a faint, intermittently visible vessel next to the opening of RCA. (a) A looming coronary artery next to the opening of RCA. Angle: RAO 30° + CRA 30° and (b) this vessel was the second LAD arising from the anomalous opening. Angle: RAO 30° + CRA 30°

Figure 4.

The anomalous LAD supplies blood to the LAD area together with the original LAD. (a) The anomalous LAD. Angle = RAO 30° + CRA 30° and (b) the anomalous and original LADs. Angle = RAO 30° + CRA 30° LAD: left anterior descending artery; RAO: right anterior oblique; CRA: cranial.

Discussion

Although similar cases have been reported, our case does not fully align with the existing literature. Previous studies have reported cases wherein the anomalous LAD originates from the proximal right coronary artery and takes a course anterior to the right ventricular outflow tract to the left anterior interventricular groove.^5,6 In this case, the LAD originates anomalously from the right coronary sinus and courses between the pulmonary artery and the aorta.

Coronary artery anomalies constitute a diverse group of congenital disorders, classified based on anomalies of origin, intrinsic anatomy, and termination. ⁷ The proximal course of an anomalous artery is a major prognostic factor. The interarterial course (between the aorta and pulmonary artery) is considered high-risk or “malignant” due to its strong association with sudden cardiac death, particularly in young individuals during exercise. ⁸ This risk is attributed to potential compression between the great vessels during exertion, a slit-like ostium, or an acute take-off angle. In contrast, courses such as retroaortic, prepulmonic, and transseptal are generally considered benign as they are not associated with the same risk of life-threatening compression. ⁹

Management of coronary artery anomalies is not uniform and must be tailored, based on the anomaly’s anatomy, presence of symptoms, and objective evidence of ischemia. ¹ For diagnosis, noninvasive imaging, particularly CCTA, is the gold standard for defining the origin and course of an anomalous artery, providing superior 3D anatomical relationships compared with traditional angiography. ¹⁰ Conservative management is a reasonable approach for asymptomatic patients with anomalies of known benign prognosis or without evidence of inducible ischemia. ¹¹ Conversely, surgical intervention is most strongly indicated for symptomatic patients or those with high-risk anatomical features, primarily an interarterial course, especially when associated with symptoms such as angina and syncope, or objective evidence of ischemia. ¹²

However, for this patient, the anomalous LAD originated from the right coronary sinus, not the proximal right coronary artery. In addition, the original LAD in this patient resembled a CTO; to the best of our knowledge, this is the first such report. ¹³ The patient exhibited a unique dual-arterial supply system, comprising a normally patent LAD originating from the left coronary artery and an additional anomalous LAD arising from the right coronary sinus. Regarding the decision of whether revascularization should be performed and which revascularization strategy should be used, a comprehensive assessment should be conducted, considering the patient’s symptoms and functional test results. The patient’s symptoms and echocardiography (ECG) results should be evaluated first. Revascularization should be considered in cases of myocardial ischemia, depending on the patient’s symptoms and current clinical condition. ¹⁴ This study has certain limitations. A functional assessment of the patient’s LAD was not performed.

Such a rare anatomical variant poses significant diagnostic challenges, leading to potential misinterpretation. With advancements in PCI techniques, the number of surgeries for CTO lesions has been steadily increasing. ¹⁵ For CTO cases, CAG alone is insufficient—particularly in patients lacking retrograde collateral circulation distal to the occluded vessel—where particular attention must be paid to the presence of an aberrant coronary artery. Therefore, multimodal imaging assessment (CCTA combined with CAG) is essential for these patients. ¹⁶ This approach not only facilitates precise visualization of the occluded vessel’s course but also enables detection of aberrant coronary artery origins, thereby preventing unnecessary revascularization procedures and vascular perforation risks.