Congenital anomaly of the coronary arteries can be benign or potentially severe, causing myocardial ischemia, infarction, and sudden death. The incidence varies between 0.3% and 1.5% in necropsy studies and coronary cineangiography.¹ The origin and proximal course of the anomalous coronary arteries are the main factors predicting severity.^2,3

This anomaly represents the second most frequent cause of sudden death of cardiovascular origin in competitive athletes.⁴ Its diagnosis is difficult, as the individual may be asymptomatic until before the lethal event.^5,3 The surgical techniques used to treat this pathology have evolved; however, there is no consensus regarding the most appropriate treatment for each type of patient.^5,6

In the case of anomalous origin of the left coronary artery with an interarterial course, surgical revascularization is recommended, regardless of documented ischemia or symptoms.⁷

The objective of this study is to report an unusual case of anomalous origin of the left coronary artery from the right coronary sinus with an interarterial course in an asymptomatic patient.

We report the case of a 47-year-old male patient, who walked and ran 3 times a week. The patient, who denied angina, dyspnea, syncope, or palpitations, sought his physician for routine exams. He denied systemic arterial hypertension, diabetes, or smoking. The physical examination was normal. Electrocardiogram was normal, and the patient had normal blood pressure. He underwent an exercise test that revealed electrocardiographic changes during exercise compatible with an ischemic response pattern, without complaints of angina, with a normal blood pressure response, without arrhythmia, and a good workload (10 METs).

Doppler echocardiography was normal. Given these exercise abnormalities, myocardial perfusion scintigraphy was requested to assess the presence of myocardial ischemia.

Myocardial perfusion scintigraphy was performed under the Bruce protocol reaching stage IV, lasting 10 minutes and 6 seconds, reaching 10 METs, and 97% of the age-predicted maximum heart rate. The blood pressure curve was normal; the patient did not report chest pain, and the electrocardiographic tracing during exercise revealed a descending ST depression of 2 mm in CM5 and 1 mm in CM5 during recovery (Figure 1).

The perfusion images, analyzed qualitatively and quantitatively using Wackers-Liu software (Yale University), were normal, and the circumferential profiles of the images showed normal distribution (Figure 2). Left ventricular ejection fraction was also normal, without segmental contractile dysfunction.

Due to the inability to clarify the electrocardiographic changes induced by exercise, coronary tomography angiography was requested (Figures 3, 5, 6, 7, 8, 9, 10 and 11). The coronary calcium score was zero. The dominance was right; the left coronary trunk was absent. The anterior descending artery was non-dominant, originating from the right coronary sinus in an independent ostium; following a course between the aorta and the pulmonary artery trunk toward the anterior wall of the left ventricle; subsequently, it followed the anterior interventricular sulcus along the usual course. The circumflex artery was very important, originating in the right coronary sinus in an independent ostium, following a retroaortic course, passing between the aorta and the left atrium and continuing through the left atrioventricular sulcus in the usual course. The right coronary artery was the dominant artery, reaching the posterior interventricular sulcus, where it gave rise to a posterior descending branch.

Preoperative coronary cineangiography was performed, which confirmed the tomography angiography findings, namely, proximal systolic narrowing of the anterior descending artery during its interarterial course; it did not reveal obstructive arterial disease (Figure 4). The patient underwent surgical revascularization of the anterior descending artery through the anastomosis of the left internal mammary artery. The surgical procedure took place approximately 6 months after diagnosis, without complications. The patient resumed his physical activities and is asymptomatic.

Anomalous origin of the coronary artery is a rare congenital heart disease. In cases of anomalous origin of the coronary artery, the coronary artery originates from the coronary sinus inappropriately, either through a separate or common ostium or through a sub-branch. There are several subtypes; in the interarterial subtype, the coronary artery follows a course between the aorta and the pulmonary artery, presenting a potential risk of sudden death. A comprehensive review published by Cheezum et al. suggests that the true prevalence of this abnormality is likely underestimated. In this series, 39% of the sample with some type of anomalous origin of the coronary artery had the interarterial subtype. There are few studies that have screened for anomalous origin of the coronary artery in the absence of clinical indications.⁸

In current guidelines, coronary tomography angiography and cardiac magnetic resonance angiography are the only methods with a class I indication. In many centers, tomography angiography is the preferred method for this diagnosis. Invasive angiography allows for greater spatial and temporal resolution, and it has a class IIa indication for diagnosing anomalous coronary artery. Functional tests, such as exercise testing and myocardial perfusion scintigraphy, analyze the functional significance of the anomalous origin on coronary flow.⁹

Grani et al. examined 46 adults (mean age of 56 years) diagnosed with anomalous origin of coronary arteries by tomography angiography, and they identified perfusion changes only in patients with concomitant coronary artery disease.¹⁰

Physical stress is preferable to assess myocardial perfusion, since most cases of sudden death attributed to anomalous origin of the coronary arteries occur with strenuous exercise. Several publications have reported a large number of false positives and negatives with these methods. Among 27 young athletes with anomalous origin of the coronary arteries described by Basso et al., 6 patients had a normal exercise test before presenting sudden death. Therefore, the absence of ischemia during stress testing cannot be seen as sufficient.¹¹

This clinical case followed current recommendations. Even in the absence of documented ischemia, due to the interarterial course of the anterior descending coronary artery, revascularization was indicated.

The objective of this study is to report an unusual case of anomalous origin of the left coronary artery from the right coronary sinus with an interarterial course in an asymptomatic patient. It is necessary to reflect on this diagnosis in young patients with symptoms of angina and syncope on exertion. Nonetheless, the diagnostic challenge is enormous, considering that a large portion of these patients do not have symptoms before sudden death; this fact requires more research to find a cost-effective means of assessment, particularly in individuals who practice intense competitive sports.