Ectopic Origin Left Circumflex-MDCT

Our patient for routine diagnostic angiography   shows origin of circumflex from proximal RCA. Vessel  though is thinner in caliber relatively   shows no significant atheromatous changes.

Case submitted by- Dr Krishna Mohan Dr Sudheer  and Dr MGK Murthy

 NORMAL CORONARY ANATOMY:

The RCA courses in the right atrioventricular groove and provides nutrient branches to the right ventricular free wall, extending to the acute margin of the heart.  In 90% of patients, the RCA supplies the posterior descending coronary artery branch at the crux of the heart, which supplies the atrioventricular (AV) node and the posterior aspect of the interventricular septum.

The first branch arising from the RCA is the conal or infundibular branch, to supply the muscular right ventricular outflow tract or infundibulum. The RCA supplies blood to the atria with a highly variable pattern of small branches. The sinus node artery arises from the proximal RCA in approximately 50% of patients.

 The left coronary artery (LCA) arises from the mid position of the left (left anterior) sinus of Valsalva The left coronary ostium is usually single, giving rise to a short, common LCA trunk that branches into the left anterior descending (LAD) and circumflex (Cx) coronary arteries.  The LAD courses in the anterior interventricular groove, giving rise to the anterior septal perforating branches as it extends toward the cardiac apex. Small branches may arise from the LAD and supply the anterior wall of the right ventricle. Diagonal branches arise from the LAD and course at downward angles to supply the anterolateral free wall of the left ventricle.

 The Cx coronary artery courses along the left AV groove, around the obtuse margin, and posteriorly toward the crux of the heart. Should the Cx coronary reach the crux of the heart and supply the posterior descending coronary artery, the left coronary system would be termed dominant. This occurs in approximately 10% of patients.

 Atrial branches may arise from the Cx coronary artery and supply the sinus node in 40% of patients. Obtuse marginal branches arise from the Cx system to supply the posterolateral aspect of the left ventricle. In an estimated 70% of patients, a coronary branch (termed ramus medianus, intermedius, or intermediate branch) arises early off the left coronary system to supply an area between diagonal branches from the LAD and obtuse branches from the Cx systems.

ANOMALIES:

 Because of considerable heterogeneity of coronary vasculature, what is considered atypical, abnormal, aberrant, anomalous, accessory, ectopic, incidental, variant, or significant is often unclear. The terms anomalous or abnormal are used to define any variant form observed in less than 1% of the general population.

INCIDENCE:

Coronary artery anomalies are found in 0.6% to 1.55% of patients who undergo coronary angiography. MDCT diagnostic  angiograms are unravelling many anomalies not appreciated before specific anomaly to our case. The ectopic origin of the LCx is a well-recognized variant, which is considered the most common coronary anomaly and can be found in approximately 0.37% to 0.7% of all patients.  The anomalous LCx most commonly arises from a separate ostium within the right sinus, or as a proximal branch of the RCA .  Although this anomaly is classified as benign and asymptomatic, and a few cases of sudden death, myocardial infarction, and angina pectoris in the absence of atherosclerotic lesions have been reported

TECHNICAL SIGNIFICANCE:

if needed, angioplasty of these anomalous  vessels is very challenging to the physician