The cardiovascular system appears at 3 weeks' gestation as a pair of cardiogenic cords. These cords migrate in a cephalad direction and form a single heart tube. Late in the fourth week of gestation, the coronary vasculature arises as isolated blood islands, which first develop near the ventricular apex. These blood islands multiply over the remaining ventricle, and then coalesce to form a primitive vascular network.

At 5 weeks, coronary buds arise from the truncus arteriosus; this undergoes septation and division to form the aorta and pulmonary trunk. Formation of coronary buds may be induced by these major vascular channels as they approach the truncus arteriosus. The lumenal continuity between the proximal coronary buds and the distal epicardial vessels forms during the seventh week of gestation, and the coronary circulation assumes its normal configuration.

The incidence of coronary artery anomalies varies between 0.2 and 1.2 per cent, depending on whether the series is based on pathological or on angiographic criteria. Anomalies of the coronary arteries may involve their origin, course, or termination.

Coronary ostia normally arise 1 cm or less above the aortic valve annulus. A high take-off refers to an ostium arising more than 1 cm above the aortic annulus; a low take-off originates from below the aortic annulus. These variations may complicate cannulation of the coronary arteries during cardiac catherization. Two coronary ostia are normally present, one located at the right sinus of Valsalva and the second at the left sinus of Valsalva; however, three or four coronary ostia are considered to be normal variants. Most commonly a conal branch arises from a third coronary ostium, rather than from its usual origin from the right coronary artery. This small, accessory conal artery is present in up to 50 per cent of normal hearts.

Coronary ostial stenosis or atresia can occur if the ostium and possibly a few millimetres of the coronary vessel fail to canalize properly. This rare condition is potentially lethal: the severity of symptoms depends on the degree of collateral flow. If an affected infant requires surgery, a subclavian artery graft should be performed, since saphenous vein bypass grafts are not successful in this age group.

An origin of the left circumflex artery from the right coronary artery or from the right coronary ostium is the most frequent anomaly occurring in otherwise normal hearts. In one series, this occurred in 26 of 45 patients (57.8 per cent) with angiographically confirmed coronary artery anomalies. The distal course of the left circumflex artery follows its normal path posterior to the aorta and into the left atrioventricular sulcus. The left main coronary artery continues only as the left anterior descending artery with its normal distribution.

This anomaly is diagnosed by coronary angiography. An avascular region in the posterior lateral left ventricle during left coronary injection suggests an anomalous origin of the left circumflex artery, assuming that there is no proximal obstruction in the left circumflex artery. Page et al. have described the ‘aortic root sign’, in which a profile view of the anomalous circumflex artery, coursing posteriorly behind the right sinus of Valsalva, is demonstrated during left ventriculography in a right anterior oblique projection.

This anomaly has not been reported as a direct cause of death, but it must be identified in patients undergoing valve surgery in order to prevent its injury during valve replacement.

Anomalous origin of the left main coronary artery from the right sinus of Valsalva is classified on the basis of the course of the left main coronary artery as it passes to the left heart. It may run anterior to the pulmonary trunk, posterior to the aorta, between the aorta and pulmonary trunk (Fig. 1(a)) 1751, or within the interventricular septum beneath the right ventricular infundibulum. The right coronary artery arises normally from the right aortic sinus. This anomaly is noted in 8.9 per cent of patients with angiographically confirmed coronary artery anomalies. Myocardial ischaemia or sudden death due to this coronary anomaly tend to occur in patients in whom the left main coronary courses between the aorta and pulmonary artery. Most sudden deaths occur after physical exertion: in one study, 13 of 16 patients (81.3 per cent) who died suddenly were engaged in or had just completed physical exercise. The mechanism of this sudden death is not clearly defined. One suggestion is that as the left coronary artery arises from the right sinus of Valsalva it forms an acute angle at its origin, resulting in compromise of the arterial lumen as it courses left along the contour of the aorta. As cardiac output rises with exercise the aorta expands, stretching the left main coronary artery and producing an occlusion of the slit-like orifice. Others have proposed that during exercise the left main coronary artery becomes compressed between the dilated aortic root and the pulmonary trunk, which is firmly anchored to the infundibular septum. The significance of haemodynamic compression between the great arteries is supported by the observation of a patient in whom the left main coronary artery arose from the proximal right coronary artery without an oblique take-off. However, there are doubts over whether a pulmonary artery under normal pressure can constrict an anomalous coronary artery perfused with systemic pressure. A symptomatic 14-year-old male with an anomalous left main coronary artery arising from the right sinus of Valsalva and traversing between the aorta and pulmonary artery underwent surgical enlargement of his left main orifice. He remained asymptomatic 9 years later, despite working in heavy construction.

This anomaly is more common in men than women, and almost all victims of sudden death are young males. Patients may present with exertional syncope, dizziness, and angina: symptoms which can mimic other cardiac abnormalities such as aortic stenosis. Physical findings such as murmurs and abnormal peripheral pulses can be helpful in the differential diagnosis. The resting ECG is normal in almost all young patients. A stress electrocardiogram should be carried to maximal effort to increase its reliability as a screening test for symptomatic patients. If evidence of myocardial ischaemia is obtained, a coronary arteriogram should be performed. If a normal maximal stress electrocardiogram is obtained in a young male with definite exercise-induced symptoms, a coronary arteriogram should still be considered to rule out this coronary anomaly.

Young patients with an anomalous left main coronary artery originating from the right sinus of Valsalva and coursing between the aorta and pulmonary artery should undergo surgery to prevent exercise-induced myocardial ischaemia and to reduce the high incidence of sudden death. Coronary artery bypass grafting to the left anterior descending artery and the left circumflex artery relieves symptoms and objective evidence of myocardial ischaemia. Surgical enlargement of a slit-like left coronary ostium may also relieve symptoms.

Both right and left coronary arteries arise from the left sinus of Valsalva in 27 per cent of patients with angiographically confirmed coronary artery anomalies. The right coronary artery courses between the aorta and pulmonary artery with a normal distal distribution (Fig. 1(b)) 1751. The left coronary artery is normal, both in its origin from the left sinus of Valsalva and in its final distribution. Presenting complaints of dyspnoea, dizziness, and exertional syncope are similar to those of patients with an anomalous left coronary artery arising from the right sinus of Valsalva and coursing between the aorta and pulmonary artery. The cause of ischaemia appears to be either compression of the anomalous artery between the aorta and pulmonary artery during exertion, or occlusion of the slit-like orifice of the anomalous artery, which is stretched by the aorta during exercise. Although patients with this anomaly have a history of myocardial ischaemia or myocardial infarction, sudden death was not seen in one autopsy series of 18 patients: surgical intervention in asymptomatic patients is not indicated. However, if the patient develops signs or symptoms of myocardial ischaemia, an operation such as aortocoronary bypass is warranted.

An anomalous left anterior descending artery can arise from the right sinus of Valsalva or the right coronary artery. It courses either between the aorta and the pulmonary artery (Fig. 1(c)) 1751 or anterior to the right ventricular infundibulum before finally reaching the anterior interventricular sulcus. The left coronary artery, arising from the left sinus of Valsalva, continues only as the left circumflex artery. In one series, this anomaly was found in 4.4 per cent of 45 patients with coronary artery anomalies confirmed by angiography. Sudden death can occur when the left anterior descending artery courses between the aorta and pulmonary artery; consequently, aortocoronary bypass is recommended. In patients with tetralogy of Fallot, the anomalous left anterior descending artery frequently courses anterior to the right ventricular infundibulum. It is important to recognize this anomaly prior to surgery, since the surgical approach may need to be altered.

In this anomaly the left coronary artery arises from the main pulmonary artery, but its distal distribution remains normal (Fig. 1(d)) 1751. The right coronary artery is normal, both in its origin from the right sinus of Valsalva and in its distal distribution. This anomaly was first reported by Brooks in 1886 in an autopsy study of two adults. In 1933, Bland et al. described a 3-month-old boy with ‘recurring attacks of dyspnoea, pallor, and profuse sweating’ in addition to an ‘acute discomfort precipitated by the exertion of nursing.’ At autopsy the left main coronary artery was found to arise from the pulmonary artery; the right coronary artery was normal. This anomaly in infants has subsequently been referred to as the Bland–White–Garland syndrome.

This anomaly was found in 10 of 3800 patients catheterized for congenital heart disease. Fontana and Edwards observed this anomaly once in an autopsy series of 357 patients with congenital heart disease. In their review of 58 patients in whom the left main coronary artery arose from the pulmonary artery, 46 patients (79 per cent) died by 13 months of age, usually from congestive heart failure. The remaining 12 patients lived longer than 15 years, but eight of these died suddenly.

This anomaly may present in infancy or in adulthood; the determining factor in the outcome is the degree of collateral circulation. In the infantile type, collateral circulation is inadequate, causing myocardial ischaemia and congestive heart failure.

During fetal and neonatal life, the pressures within the pulmonary artery and aorta are approximately equal; consequently, the pulmonary artery perfuses the left main coronary artery. Early in life, the pulmonary artery pressure begins to fall; at 12 months it is approximately one-quarter that of the aortic pressure. Survival depends on collateral channels forming between the right coronary artery and the anomalous left coronary artery, providing retrograde flow in the left main coronary artery, with arterial blood being supplied by the right coronary artery. If collateral circulation between the right and left coronary arteries is well established, the patient may survive to adulthood, despite the presence of a left-to-right shunt through the coronary circulation. The transition from antegrade to retrograde flow within the left main coronary artery is frequently associated with death.

The patient is relatively asymptomatic in the first few weeks of life, but the progressive fall in the pulmonary artery pressure produces symptoms such as angina-like episodes associated with feeding, paroxysmal crying, dyspnoea, tachypnoea, and restlessness at 2 to 3 months of age. Poor feeding results in minimal weight gain. Most patients deteriorate because of congestive heart failure and recurrent pulmonary infections. Mitral regurgitation can also occur due to ischaemia or infarction of the papillary muscles.

Physical examination often reveals signs characteristic of heart failure such as cardiomegaly, hepatomegaly, and rales. Auscultation may reveal a non-specific systolic murmur at the base or an apical systolic murmur due to mitral regurgitation. The ECG frequently demonstrates Q waves and ST segment elevation in the lateral precordial leads, indicative of anterolateral infarction. The chest radiograph shows cardiomegaly and interstitial pulmonary oedema.

Adult patients are frequently asymptomatic, and they may experience dyspnoea or angina only during strenuous physical exertion. On auscultation, a continuous precordial murmur may be detected, as well as the apical pansystolic murmur of mitral regurgitation. The resting ECG is almost always abnormal with ST segment changes. The chest radiograph may be normal, or may show cardiomegaly. In adults there is a high incidence of sudden death: this was the initial clinical manifestation in 8 of 10 patients who died from anomalous origin of the left main coronary artery from the pulmonary artery.

In both forms of this anomaly, cardiac catheterization with angiography is diagnostic. Aortic root injection shows a large right coronary artery with retrograde filling of the left main coronary artery through collateral vessels. Absence of retrograde flow through the left main coronary artery and into the pulmonary artery indicates poor collateral flow. In the infant, apparent absence of retrograde flow may be due to the persistence of elevated pulmonary artery pressure and antegrade flow in the left coronary artery, particularly if there is associated mitral regurgitation.

The mortality rate in untreated infants during the first year of life is as high as 90 per cent. Simple ligation of the left main coronary artery produces a single coronary arterial system, with variable outcome: more recent operations aim to maintain a two coronary artery system. In one such procedure, the ostium of the left main coronary artery is excised with a rim of pulmonary artery and is reimplanted directly into the aorta. Alternatively, the left main coronary artery can be ligated and a reversed saphenous vein graft placed between the aorta and the left main coronary artery, distal to the ligature. Finally, the left main ostium can be arterialized by creating an aortopulmonary window and baffling it within the main pulmonary artery to the left main ostium.

This anomaly is less common than anomalous origin of the left main coronary artery from the pulmonary artery. The right coronary artery arises from the right pulmonary sinus, but its distal distribution is normal. The left coronary artery is normal in its origin and distribution.

Patients with these coronary artery anomalies usually do not complain of angina; physical examination may only disclose a continuous murmur with diastolic accentuation. Definitive diagnosis is made by angiography: injection of the left coronary artery demonstrates retrograde filling of the anomalous right coronary artery through collaterals. Since cardiac arrest has been reported in patients with this anomaly, surgery is recommended. The procedure of choice is excision of the right coronary ostium with a rim of pulmonary artery and its reimplantation directly into the aorta. In older patients proximal ligation and aortocoronary bypass may be performed.

A single coronary artery can follow the course of the normal right or left coronary artery, can divide into two branches with each branch following either the right or left coronary artery, or it may not correspond with any normal coronary artery pattern. This anomaly was noted in two of nine patients with coronary artery anomalies confirmed by angiography. Some patients are asymptomatic; others may present with congestive heart failure or sudden death. Diagnosis is confirmed by cardiac catheterization and angiography. In these patients proximal coronary atherosclerosis is especially serious, since a second coronary artery is not present to contribute collaterals. Aortocoronary bypass is performed in symptomatic patients with confirmed coronary atherosclerosis.

A congenital coronary artery fistula is a communication between a coronary artery and an atrium, ventricle, pulmonary artery, or superior vena cava. During embryonic development, intratrabecular spaces of the myocardium communicate with the coronary arteries. Coronary artery fistulae may form if a large intratrabecular space persists; this results in a connection between the coronary artery and a cardiac chamber. In one series the fistulous tract arose from the right coronary artery in 56 per cent of patients and from the left coronary artery in about 40 per cent. In 90 per cent of the patients the fistula terminates in the venous side, the most common site being the right ventricle, followed by the right atrium and pulmonary artery.

The clinical status of patients varies from asymptomatic to severe congestive heart failure, mainly due to the left-to-right shunt. Many infants and children are asymptomatic; their fistulae are discovered only after a murmur is heard on a routine physical examination. Cardiac catheterization will delineate the fistula, which then should be surgically oversewn or divided.

Congenital aneurysms of the sinus of Valsalva are thought to arise due to defective development of aortic elastic tissue above the aortic valve annulus. Aortic pressure gradually causes an aneurysm to form at the thinned aortic wall, most commonly at the right aortic sinus. The aneurysm is often described as having a ‘wind-sock’ appearance. Rupture of the aneurysm forms a fistula, which usually leads into a low pressure chamber such as the right ventricle or right atrium. The majority of patients have associated cardiac abnormalities, such as ventricular septal defects and aortic valve anomalies.

Unruptured sinus of Valsalva aneurysms are rarely discovered prior to angiography, which is usually performed for associated cardiac lesions such as ventricular septal defects. Acute rupture results in sudden chest pain and dyspnoea, as well as the appearance of a loud, continuous murmur. A widened pulse pressure may suggest aortic incompetence. Echocardiography can help confirm the diagnosis, while cardiac catherization will define the fistula and any associated cardiac anomalies, as well as define the size of the shunt.

A combined surgical approach is recommended: the aneurysm is resected through the involved cardiac chamber and the fistula is closed through the aorta. Additional procedures such as closure of a ventricular septal defect or an aortic valve reconstruction or replacement may be necessary.

Ectopia cordis is defined as a heart which is partially or completely outside the thorax. It was first described by Stensen in 1671. There are four basic types of ectopia cordis classified according to the location of the heart: cervical, thoracic, thoracoabdominal, and abdominal. Cervical ectopia is found only in malformed fetuses, and only one case of true abdominal ectopia has been reported. In one review of ectopia cordis, 62.5 per cent of all cases were of the thoracic type. These anomalies are often associated with other congenital defects, such as Cantrell's syndrome, which includes a midline, supraumbilical abdominal wall defect, a defect of the lower sternum, deficiency of the anterior diaphragm, a defect in the diaphragmatic pericardium, and congenital intracardiac defects. This syndrome is thought to result from defective mesodermal development at 14 to 18 days of embryonic life.

The objective of surgical treatment is to replace the heart into the mediastinum. This operation may be complicated by the presence of other associated defects such as omphalocele, and diaphragmatic and sternal defects, which are present in thoracoabdominal ectopia cordis. Since the thoracic cavity is often too small to accept the heart, chest wall reconstruction may be necessary.

Congenital cardiac diverticula can occur in any one of the four cardiac chambers. Atrial diverticula can cause arrhythmias, and if on the left side of the heart, they can be a source of cerebral emboli. Muscular ventricular diverticula can rupture or lead to congestive heart failure. Ventricular diverticula are frequently associated with other congenital abnormalities, such as midline thoracoabdominal defects. Surgical resection, usually with cardiopulmonary bypass, is the recommended therapeutic approach.

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