Ectopic Origin of Left Coronary Ostium from Left Ventricle, with Occlusive Membrane

Abstract

Congenital atresia of the left main coronary artery, a condition in which the left main trunk is developed but has been occluded since birth, is a rare coronary anomaly. Herein, we describe this anomaly's association with a subannular location of an obliterated left main ostium in a patient with a bicuspid aortic valve and severe aortic stenosis. The patient underwent successful surgery. We discuss the embryologic implications of congenital atresia of the left main coronary artery, in view of the exceptional anatomic features of this condition. To our knowledge, this is the 1st report of a left coronary artery that was found to arise from the left ventricle.

Congenital atresia of the left main coronary artery (CALM) is a condition in which the left main trunk is developed but has been occluded since birth.¹ This extremely rare anomaly can present as an isolated feature or in association with other congenital cardiac abnormalities, most frequently supravalvular aortic stenosis.² Isolated, anomalous subvalvular origin of the right coronary artery (RCA) from the left ventricular outflow tract (LVOT) has been reported only once in the medical literature. Herein, we report what we believe is the 1st case of the left coronary artery (LCA) arising from the LVOT, and we discuss the embryologic implications of congenital atresia of the LCA.

Case Report

In November 2006, a 51-year-old man was admitted to our hospital with progressive chest pain and dyspnea during rest and exercise (New York Heart Association functional class III–IV). His medical history included hypertension and a severely stenotic bicuspid aortic valve.

Selective coronary angiography showed a dominant RCA with a normal origin from the right sinus (Fig. 1). However, no coronary artery could be found to arise from the left sinus. Instead, the LCA appeared to fill through a single branch (diameter, 2.5 mm), with origination from the proximal portion of the RCA and with a course into the upper ventricular septum. This unusually large septal branch trifurcated into branches that fed 3 independent sections of the LCA (Fig. 1): the distal left anterior descending coronary artery (LAD); the mid-LAD with 2 diagonal branches; and the proximal LAD with the ramus intermedius, the circumflex, and the left main trunk (Figs. 1 and 2). The left main trunk ended in a blind pouch, which was occluded by a valve-like membrane that showed systo–diastolic motion. The contrast medium cleared slowly from the left main trunk.

Fig. 1 Preoperative coronary angiogram (right anterior oblique projection) shows 3 intraseptal collateral vessels arising from the right coronary artery (RCA) and supplying the left coronary arterial system.

Fig. 2 Preoperative coronary angiogram (left anterior oblique projection) shows collateral filling of the proximal left coronary arterial system via intraseptal collateral vessels.

Transesophageal echocardiography showed a preserved left ventricular ejection fraction of 0.55 and moderate, concentric hypertrophy of the left ventricle. The aortic valve appeared bicuspid, with severe calcification of the leaflets and annulus, associated severe stenosis (valvular area, 0.5 cm²; mean transvalvular gradient, 61 mmHg), and mild insufficiency. Color-flow Doppler echocardiographic analysis revealed retrograde flow that filled the left main trunk. The proximal left main trunk appeared to be slightly lower than the RCA in the aortic root—within the LVOT.

The patient was referred for aortic valve replacement and coronary artery bypass grafting. At surgery, the right coronary ostium was found to have a normal origin from the right sinus, but the left coronary ostium could be found neither in its normal location nor anywhere within or above the aortic sinuses. Underneath the left posterior commissure, a whitish, depressible membrane—evident beneath the aortic valve annulus —bulged into the LVOT after retrograde administration of cardioplegic solution (Fig. 3). Aortic valve replacement was completed in a usual fashion, with use of a porcine Mosaic ULTRA® #23 stented aortic prosthesis (Medtronic Inc.; Minneapolis, Minn). Two coronary bypasses were performed: a left internal thoracic artery graft to the LAD, and a saphenous vein graft to the 1st obtuse marginal branch.

Fig. 3 Intraoperative photograph, taken after the retrograde administration of cardioplegic solution, shows the out-pouching of the subannular membrane (arrowheads) that covers the left main coronary ostium.

LVOT = left ventricular outflow tract

Postoperative magnetic resonance angiography (Fig. 4) confirmed the presence of a pouch that covered the left main trunk, below the prosthetic aortic annulus and within the LVOT. Diminutive LAD and circumflex coronary arteries were noted. The LCA and RCA clearly originated at different levels—the LCA from below the annular plane of the aortic valve, and the RCA from above. The bypasses to the LAD and obtuse marginal branch were patent. Postoperatively, the patient recovered well, returning to work 4 weeks after the procedure with normal exercise tolerance (NYHA functional class I).

Fig. 4 Postoperative coronary magnetic resonance angiogram shows the subannular origin of the left coronary artery ostium and the normal origin of the right coronary artery.

AV = aortic valve; LCA = left coronary artery; LV = left ventricle; LVOT = left ventricular outflow tract; RCA = right coronary artery; RV = right ventricle

Discussion

Coronary artery anomalies are uncommon, with an estimated worldwide incidence of 5.64% according to Angelini and colleagues,¹ who evaluated a continuous series of 1,950 patients by means of coronary angiography.

Although congenital atresia of the left main coronary artery (CALM) is frequently described as atresia of the left main coronary artery (LMCA), the left main trunk and, importantly, the distal LCA branches are indeed present, while the left main ostium is atretic. Congenital atresia of the LMCA needs to be differentiated from single coronary artery, in which a single, common trunk, located at any sinus of Valsalva, supplies the entire heart: in CALM, the 3 main coronary arteries (RCA, LAD, and circumflex) are normally developed (none is absent—and, in our patient, all were well-developed), but there is anomalous origination of all 3 from a single ostium.¹

Isolated subvalvular origin of a coronary artery from the LVOT is an even rarer congenital occurrence.¹ Only 1 case of anomalous origin of the RCA from the left ventricle has been reported in the medical literature; no other case has been reported regarding such an origin of the LCA.

During human embryogenesis, the coronary arteries first appear as originating from the aortic root at about the 30th day of intrauterine life.¹ Congenital atresia of the LMCA can present clinically early in life, in adulthood, or never, depending on the adequacy of the collateral circulation from the RCA. Our patient developed symptoms of angina and heart failure only after the aortic stenosis became severe, during adulthood. Patients with CALM are at increased risk of sudden death, especially if they have ischemia.³

At surgery, a membrane just below the left posterior commissura of our patient's bicuspid aortic valve was noted to bulge into the LVOT. When an anomalous LCA arises from the LVOT in the absence of ostial atresia, fistulous coronary-to-left ventricular flow is generated, with the likely development of coronary steal. Surgery is indicated in such symptomatic patients: ligation of the main trunk is required, together with bypass grafting of the distal LCA branches.

In cases of isolated CALM, the left main trunk, the LAD, and the circumflex artery are in their normal anatomic positions, although the left coronary ostium is atretic. In our patient, postoperative magnetic resonance angiography confirmed the presence of a blind subannular trunk of the LCA that ended at the out-pouching membrane. An extensive review of the medical literature regarding congenital anomalies of the coronary arteries revealed no other case in which CALM was associated with a subvalvular origin of the left main trunk.

The association of bicuspid aortic valve with coronary anomalies (well reported in the medical literature) was the object of experimental studies in inbred hamster families that were selected because of a high incidence of bicuspid aortic valve.^1,4 It is likely that the embryogenesis of the dysplastic aortic valve in our patient was related to the later mechanisms of LCA ostial atresia and of the LCA's apparent origin from the LVOT. We hypothesize that our patient was born with an abortive 3rd leaflet (the left) and that its dysplastic tissue eventually adhered to an initially well-developed LMCA trunk (suggested by the large ostial LCA diameter), which resulted in the delayed acquisition of CALM. This assumption would best explain the presence of a single collateral source of filling from the RCA and the interruption of the LAD into the 3 segments that connected individually to the trifurcating 1st septal branch.

Such unusual intrinsic anatomy of the LCA cannot be expected to occur when LCA occlusion develops later in life. In our patient's case, the presence of a well-developed left main trunk supports the likelihood of prograde flow at the LCA ostium during his embryonic life. The systo–diastolic excursions of the whitish, obstructive LCA membrane also suggest that the membrane was valvular tissue. If it is correct that the LCA originated from the left ventricle—a highly unlikely or “impossible” site of origin of an ectopic LCA—then the location of the obliterated ostium should be inside the diminutive aortic left coronary sinus, not in the subvalvular area.

The true evolution of the abnormality that made the findings in this patient possible will remain a matter of conjecture. This case exemplifies the collaboration among practitioners of cardiac surgery, cardiac imaging, and cardiology that enables the formulation of a precise operative approach and an excellent postoperative result.