CLINICAL HISTORY
A 56-year-old Caucasian man with a history of intermittent atrial fibrillation had no history of myocardial infarction or angina. The patient had a normal electrocardiogram and treadmill stress test three years earlier and was taking no medications at the time of diagnosis. The patient’s blood pressure was within normal range, and he was slightly bradycardic, with a heart rate at 52 beats per minute.
IMAGING FINDINGS
Discretionary multislice CT coronary angiography was performed on a 64- slice Toshiba Aquilion scanner using a routine injection protocol to evaluate for coronary artery disease. CT coronary angiography demonstrated a large single coronary artery trunk arising from the right coronary cusp. The trunk immediately bifurcated into right and left coronary arteries. The right coronary artery continued as a dominant vessel, giving rise to posterior descending and posterolateral arteries. Moving anterior to the main pulmonary trunk and then following the course of the left atrioventricular groove, the left coronary branch gave rise to a small anterior descending artery and multiple marginal branches supplying the anterior, anterolateral, and lateral walls of the left ventricle. No significant coronary artery stenosis was seen.
DIAGNOSIS
Anterior variant of single right coronary trunk.
DISCUSSION
Isolated coronary artery anomalies are relatively rare, arising in about 1% of patients without other congenital cardiac malformations. Single coronary anomalies are one of the rarest varieties, with incidence of absent left main coronary ostium at 0.05% to 0.4% of this selected population. Some assert that the absence of the left ostium or anomalies in the origin of the left coronary artery are primarily related to congenital malformation of the aortic valve. Others claim that obstruction of the left ostium occurs through fusion of the left aortic cusp to the aortic wall.
In patients with an absent left coronary ostium, four variations in the initial course of the LAD arising from the RCA are possible: anterior, interarterial, septal, and, rarely, posterior (retroaortic). In the anterior variant, the most common of the four, the LAD courses anterior to the right ventricular infundibulum. In the septal variant, it courses within the ventricular septum beneath the right ventricular infundibulum.
The interarterial type can be life-threatening, as the LAD courses between the aorta and the main pulmonary trunk. Because a left main artery arising from the right coronary is supplying a large area of the myocardium, this anomaly is associated with increased incidence of various cardiac events including angina pectoris, myocardial infarction, arrhythmias, syncope, and congestive heart failure. It is also associated with increased risk of sudden death, secondary to decreased coronary flow reserve and other anatomical variants, including compression of the artery by the pulmonary trunk or aortic wall.
Condensed from “Diagnosis of variants of single right coronary trunk using 64 multidetector computed tomography,” (Radiology Case 2008 Nov;2[5]:19-22). The full case can be reviewed online at http://www.radiologycases.com/index.php/ radiologycases/article/view/90. Contributing authors Drs. Ashley E. Kemp and Farhood Saremi are affiliated with the division of cardiothoracic imaging at the University of California, Irvine.
BIBLIOGRAPHY
Datta J, White CS, Gilkeson RC. Anomalous coronary arteries in adults: depiction at multi-detector row CT angiography. Radiology 2005;35(3):812-818.
Saremi F, Abolhoda A, Ashikyan O. Arterial supply to sinuatrial and atrioventricular nodes: imaging with multidetector CT. Radiology 2008;246(1):99-107.
