The incidence of an anomalous coronary artery is approximately 1% in the general population. An anomalous right coronary artery (RCA) arising from the left anterior descending artery (LAD) is very rare, and has previously been considered a variant of a single coronary artery. We report a unique case of an anomalous right coronary artery originating from the left anterior descending artery. The anomaly was discovered incidentally. Cardiac catheterization was performed for preoperative evaluation of coronary anatomy in a patient with severe mitral regurgitation due to endocarditis. It is particularly important to identify coronary anomalies preoperatively, as the surgical approach may need to be altered. Case Report. A 39-year-old male with a history of cocaine abuse presented to the emergency room with fever, headache, weakness and visual changes. Lumbar puncture was consistent with bacterial meningitis. Blood cultures were positive for S. pneumonia. The electrocardiogram showed sinus tachycardia. There was a holosystolic murmur on physical examination, and a mitral valve vegetation was seen on transthoracic echocardiography. The patient was treated with antibiotics for pneumococcal endocarditis and meningitis. Transesophageal echocardiography showed a 2 x 2 cm mitral valve vegetation attached to the posterior leaflet, perforation of the anterior mitral leaflet and severe mitral regurgitation. Cardiac catheterization was performed prior to mitral valve surgery. Coronary angiography showed no atherosclerotic disease. The left coronary artery originated from the left coronary cusp. The left main, the left anterior descending (LAD) and the left circumflex (LCx) arteries were normal. An anomalous vessel was seen originating from the LAD, which followed the course of a typical mid- to distal right coronary artery (RCA). This anomalous RCA originated from the mid-LAD, distal to the first septal perforator. The anomalous RCA traveled along the free wall of the right ventricle, into the atrioventricular groove, and gave rise to a posterior descending artery (PDA) (Figures 1 and 2). There was also a separate small proximal RCA originating from the right coronary cusp, with conus, right atrial and right ventricular branches (Figure 3). Discussion. The incidence of coronary artery anomalies in reported series ranges from 0.6–1.3%.1,2 The largest angiographic series of 126,595 patients, by Yamanaka and Hobbs, reported a 1.3% incidence of anomalous coronary artery. The most common anomaly was a separate origin of the LAD and LCx, with an incidence of 0.41%, followed by the LCx arising from the RCA, with an incidence of 0.37%.1 In a series of 13,010 patients, Topaz et al. reported a 0.61% incidence of anomalous coronary artery.2 In this series, separate origin of the LAD and LCx was not considered an anomaly. The most common anomaly was anomalous origin of the RCA, with an incidence of 0.38%.2 The origin of an anomalous RCA may be from the left sinus of Valsalva, the posterior sinus of Valsalva, the ascending or descending thoracic aorta, the pulmonary artery, or the left ventricle.1–4 The RCA may also arise from the left main coronary artery, the LAD or the LCx.5–12 Origin of the RCA high above the right coronary sinus is not considered anomalous. Most of these anomalies are considered benign and are discovered incidentally. However, origin of the RCA from the left sinus of Valsalva, which then follows an interarterial course between the aorta and the main pulmonary artery, is considered malignant and has been associated with angina and sudden death.13 Atherosclerotic disease does not appear to be increased in patients with anomalous coronary arteries; in particular, the anomalous vessel does not appear to be predisposed to develop atherosclerosis.2,14 However, there is an association with other congenital heart disease, in particular, bicuspid aortic valve and mitral valve prolapse.2 Origin of the RCA from the LAD is very rare. Fewer than 10 cases have been reported in the literature.7–12 Prior case reports have considered origin of the RCA from the LAD to be a variant of a single coronary artery. Previous cases have not demonstrated any additional coronary arteries, either by aortography or multidetector computed tomography. Our case is the first described in which an anomalous mid- to distal RCA originates from the mid-LAD, with a coexisting separate proximal RCA which originates from the right coronary sinus. The PDA arises from the anomalous vessel. Because the ultimate source of the PDA is the left coronary artery, we considered this to be a left dominant system. This anomaly was discovered incidentally and is likely clinically benign. It is unclear if our patient also had underlying mitral valve disease, such as mitral valve prolapse, which predisposed him to developing endocarditis. Subsequently, the patient underwent successful mitral valve replacement. Postoperative transesophageal echocardiography showed minimal mitral regurgitation and normal left ventricular function. Conclusion. This is the first report of an anomalous RCA originating from the mid-LAD, with a coexisting separate proximal RCA originating from the right coronary cusp. This anomaly is likely clinically benign.
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