Multiple variations of congenital anomalies of the coronary arteries exist that may occur in isolation or in association with other congenital anomalies. They can cause myocardial ischaemia. A rare but potentially lethal condition is the anomalous origin of the left coronary artery from the pulmonary artery. As pulmonary pressures fall in newborns with this condition, myocardial perfusion becomes dependent on collaterals from the right coronary circulation.1
Coronary Artery Fistulae
Fistulae arise from the right coronary artery (RCA) or its branches in about 50% of cases; the remaining fistulae arise from the left anterior descending artery (LAD) or the left circumflex artery (LCX) or their branches, or they have multiple origins. The fistula drains into the right ventricle in 41%, the right atrium in 26%, the pulmonary artery in 17%, the left ventricle in 3% and the superior vena cava in 1%.2 The most common haemodynamically significant coronary abnormalities are coronary artery fistulae.2 A left-to-right shunt exists in more than 90% of cases. About 50% of patients with a coronary artery fistula remain asymptomatic; the rest develop congestive heart failure, infective endocarditis, myocardial ischaemia or rupture of an aneurysm.2
Anomalous Origin of the Left Coronary Artery from the Pulmonary Artery
These patients may present with ischaemic symptoms or symptoms of heart failure from an ischaemic cardiomyopathy in infancy. They may present in the neonatal period or later in infancy or childhood. Most patients in whom the origin of the left coronary artery (LCA) is the main pulmonary artery manifest congestive heart failure and myocardial ischaemia in the first four months of life.2 This coronary anomaly is rarely seen in adults. In children, the diagnosis of coronary anomalies may often be made by echocardiography with colour flow Doppler.3–5 About 25% survive to adolescence or adulthood but develop mitral regurgitation, angina or congestive heart failure.6 Aortography typically shows a large RCA with absence of a left coronary ostium in the left aortic sinus. Selective left coronary angiography is very difficult but could be performed with left amplatz via pulmonary artery (author‘s experience). During the late phase of the aortogram, patulous LAD and LCX branches fill by means of collateral circulation from RCA branches.
A retrograde flow from the LAD and LCX opacifies the left main coronary artery (LMCA) and its origin from the main pulmonary artery. The clinical course of the patient tends to be more favourable if extensive collateral circulation exists. In rare instances, the RCA may arise from the pulmonary artery. The treatment is surgical, with reimplantation of the anomalous coronary or aortocoronary bypass.
Anomalous Origin of the Coronary Artery from the Contralateral Sinus
This anomaly – origin of the LCA from the proximal RCA or the right aortic sinus with subsequent passage between the aorta and the right ventricular outflow tract – has been associated with sudden death during or shortly after exercise in young persons (see Figure 1).7–11 The increased risk of sudden death may be due to acute take-off angles of the aberrant coronary arteries or possible compression between the pulmonary trunk and aorta. After its aberrant origin, the LCA takes an abrupt leftward turn and tunnels between the aorta and the right ventricular outflow tract. Sudden death is thought to result from transient occlusion of the anomalous LCA, caused by an increase in blood flow through the aorta and pulmonary artery that occurs during exercise and creates either a kink at the sharp leftward bend or a pinchcock mechanism in the tunnel. Origin of the RCA from the LCA or left aortic sinus with passage between the aorta and the right ventricular outflow tract is somewhat less dangerous (see Figure 2); however, this anomaly has also been associated with myocardial ischaemia or sudden death, presumably through the same mechanism.9–12 In rare cases of anomalous origin of the LCA from the right aortic sinus, myocardial ischaemia may occur even if the LCA passes anterior to the right ventricular outflow tract or posterior to the aorta (i.e. not through a tunnel between the two great vessels).13
The course of the anomalous coronary arteries is easily assessed by angiography in the right anterior oblique (RAO) view. There are four common courses for the anomalously arising LCA from the right sinus of Valsalva, one common course for the anomalous RCA arising from the left sinus of Valsalva and one common course for the anomalous LCX arising from the right sinus of Valsalva. The anomalous LCA arising from the right sinus of Valsalva may take a septal, anterior, interarterial or posterior course.14
The posterior course of the anomalous LCA arising from the left sinus of Valsalva is similar to the course of the anomalous LCX arising from the right sinus of Valsalva, whereas the common interarterial course of the anomalous RCA from the left sinus of Valsalva is similar to the interarterial course of the anomalous LCA arising from the right sinus of Valsalva.
When either the LCA or the LAD arises anomalously from the right aortic sinus, another angiographic method to identify the course of the anomalous vessel is to first pass a catheter into the main pulmonary artery and then perform an arteriogram of the aberrant coronary artery in the steep anteroposterior (AP) caudal projection. This places the aberrant coronary artery, the rightward and anterior pulmonary valve and the leftward and posterior aortic valve all in one plane. From this ‘laid-back aortogram’, which can be used even when mapping the course of anomalous coronary arteries in transposition of the great vessels, it is usually possible to confirm whether the course of the aberrant coronary artery is between the great vessels. Although angiography is useful for establishing the presence of anomalous coronary arteries, transoesophageal echocardiography and multidetector-row computed tomography (MDCT) may also be important adjunctive diagnostic tools for establishing the course of the vessels.15
Single Coronary Artery
Although there are numerous variations of this anomaly,16 it assumes haemodynamic significance when a major branch passes between the aorta and the right ventricular outflow tract (see Figure 2).
The coronary arteries may originate directly from the aorta, but their origins can be in unusual locations. The cannulation of the origin of these vessels may be problematic. These anomalies occur in about 0.5–1.0% of adult patients undergoing coronary arteriography.17
The Left Circumflex Artery Originating from the Right Aortic Sinus
In a series of nearly 3,000 patients, this anomaly was found in 0.67%.18,19 The anomalous LCX generally arises posterior to the right coronary artery and courses inferiorly and posteriorly to the aorta to enter the left atrioventricular groove. An interarterial course for an anomalous LCX originating from the right sinus of Valsalva is extremely uncommon.
Origin of All Three Coronary Arteries from One Aortic Sinus with Multiple Separate Ostia
This rare anomaly is similar to a single coronary artery. There is absence of a coronary ostium in either the left or right aortic sinus. The missing vessels arise in the contralateral aortic sinus, but instead of arising as a single coronary artery they arise through two or even three separate ostia.
High Anterior Origin of the Right Coronary Artery
This anomaly is commonly encountered but of no haemodynamic significance. The inability to engage the ostium of the RCA selectively from conventional catheter manipulation raises the question of this superior origin of the RCA above the sinotubular ridge. Forceful non-selective injection of contrast medium into the right sinus of Valsalva may reveal the anomalous take-off of the RCA, which can then be selectively engaged with an amplatz left catheter (see Figure 3).