Congenital absence of left circumflex artery with a dominant right coronary artery

Abstract

Case 1: a 40-year-old man was admitted to our hospital with progressively worsening post myocardial infarction angina. Cardiac catheterisation was performed, which showed total occlusion of the left anterior descending artery (LAD) and the left circumflex artery (LCX) was not visualised. The right coronary artery (RCA) was a large artery supplying the left ventricular inferior and posterolateral walls and filling the LAD artery in retrograde. The patient was referred for coronary artery bypass grafting. Peroperative findings confirmed the angiographic evidence of congenitally absent LCX artery.

Case 2: a 39-year-old man with a family history of premature coronary artery disease underwent coronary angiography for the work-up of chest pain. A coronary angiogram showed normal LAD artery and absence of left circumflex system. The RCA was superdominant. An aortogram confirmed no anomalous origin and true absence of LCX artery.

BACKGROUND

Congenital absence of left circumflex artery (LCX) is a very rare vascular anomaly with very few cases reported in the literature. We had two cases with this anomaly and one of them presenting with myocardial infraction, which is only the second case of this kind in the literature.

CASE PRESENTATION

Case 1: a 40-year-old man had an inferior wall myocardial infarction for which he received thrombolytics. Subsequently he developed post myocardial infarction angina, which progressively worsened over a period of 3 weeks; later, he presented to our hospital for further management. He was a known diabetic and hypertensive for 3 years. He had a 20 pack/year history of smoking.

Case 2: a 39-year-old man presented for the work-up of coronary artery disease with history of left-sided chest pain on exertion as well as on rest. He had a family history of premature coronary artery disease.

INVESTIGATIONS

Case 1: an electrocardiogram showed Q waves and T wave inversion in leads III, aVF. Echocardiography showed severely reduced left ventricular systolic function. Inferior and posterior segments were akinetic, anterior, lateral and septal segments were hypokinetic. Moderate mitral regurgitation. Cardiac catheterisation was performed which showed total occlusion of the left anterior descending artery (LAD) artery and the LCX artery was not visualised (fig 1). The right coronary artery (RCA) was a large artery with 80% obstruction in mid vessel, supplying the left ventricular inferior and posterolateral walls and filling the LAD artery in retrograde (fig 2).

Figure 1.

Left coronary angiogram in left anterior oblique (LAO) view with caudal angulation showing absence of left circumflex artery.

Figure 2.

Right coronary angiogram in left anterior oblique view showing super dominant artery with 70% lesion in mid vessel and filling the occluded left anterior descending artery in retrograde.

Case 2: a coronary angiogram showed a normal LAD artery and absence of left circumflex system (fig 3). The RCA was superdominant (fig 4). An aortogram confirmed no anomalous origin and true absence of LCX artery (fig 5).

Figure 3.

Left coronary angiogram in right anterior oblique (RAO) view with caudal angulation showing absent left circumflex artery.

Figure 4.

Right coronary angiogram in right anterior oblique (LAO) view showing large right coronary artery with large branches supplying the left ventricular posterolateral wall.

Figure 5.

Aortic root angiogram showing absent left circumflex artery.

DIFFERENTIAL DIAGNOSIS

Ostial total occlusion of left circumflex artery is the differential diagnosis of total agenesis of the left circumflex artery.

TREATMENT

Case 1: the patient successfully underwent coronary artery by pass grafting. Peroperative findings confirmed the angiographic evidence of congenitally absent LCX artery (fig 6).

Figure 6.

Peroperative finding of absence of left circumflex artery in the atrioventricular groove.

Case 2: lifestyle modification was advised for risk factor management.

OUTCOME AND FOLLOW-UP

Case 1: postoperatively the patient remained in good health at the time of discharge and on subsequent clinic visits.

Case 2: on subsequent clinic follow-ups the patient remained in good health.

DISCUSSION

Most coronary artery anomalies are discovered as incidental findings during coronary angiographic study or at autopsy with incidence rate of 0.64% to 1.3% reported in the literature.^1,2 Coronary anomalies may be benign or clinically significant as in our case.

Yamanaka and Hobbs described 126 595 patients undergoing cardiac catheterisation between 1960 and 1988.³ Separate origins of the left anterior descending and left circumflex arteries from the left sinus of Valsalva was the most common anomaly, occurring in about 0.41% of the patients studied.

Absence of the left circumflex artery is a very rare congenital anomaly with only a few case reports in literature^4–9 with a reported frequency of only 0.003% in all patients who underwent coronary angiography.³

In this condition, lateral and posterior aspects of the left ventricle are supplied by a superdominant right coronary artery; a large diagonal artery and a long right coronary artery continuing along the atrioventricular groove.³

If the left circumflex artery cannot be visualised during coronary angiography, either an ostial total occlusion or congenital agenesis should be suspected. Anomalous origin of the left circumflex artery is diagnosed when the artery is not visualised during left coronary injection in the absence of proximal occlusion, and at the same time the ostium of the circumflex artery is visualised separately from right sinus Valsalva or as an extension of the right coronary artery.^10,11 CT angiography has recently emerged as a study of choice for coronary anomalies, which can delineate the origin, course of the vessel and its relation to surrounding structures very precisely.

In our case report one of the patients had peroperative confirmation of the absence of the left circumflex system. However, our second case of absent left circumflex artery did not undergo CT angiography for confirmation; additionally we do not have intravascular ultrasound (IVUS) at our centre, but the angiographic findings that supported congenital agenesis rather than proximal occlusion were absence of any stump, no collateral filling of the left circumflex system, supradominant right coronary artery and absence of wall motion abnormalities on the left ventriculogram.

LEARNING POINTS

• Angiographic recognition of coronary artery anomalies prior to surgery is of great importance.

• The cardiac surgeon must be aware of the abnormal anatomy in order to avoid accidental ligation or transaction at the time of surgery

• Absent left circumflex artery is a benign condition, but patients can present with chest pain and may have myocardial ischaemia or other life-threatening conditions.