ALCAPA is the most common causes of myocardial ischemia and infarction in children. The left coronary artery usually arises from the left posterior sinus of the pulmonary artery (Fig. 31.3). It is more frequently seen in males with a male-to-female ratio of 2.3:1 and an incidence of 1:300,000. This anomaly is rarely recognized in the neonatal period because the pulmonary pressures and oxygen saturation are similar to that of the systemic pressures and oxygenation. Thus, coronary ischemia does not manifest. After the neonatal period, the pulmonary pressure decreases progressively reducing coronary perfusion and eventually causing a reversal of flow to the pulmonary artery (PA) (coronary steal). The steal phenomenon not only decreases left ventricular (LV) function but also increases the end-diastolic pressure of the left ventricle. The decreased oxygen content of the blood originating from the PA aggravates LV ischemia. Unrepaired ALCAPA leads to dilation, infarction, or fibrosis of the LV. Fibrosis can lead to mitral regurgitation. The RCA is usually enlarged, with a normal origin. Collateral circulation is crucial to compensate this disease. Collaterals run over the right ventricular outflow tract (RVOT) or through the interventricular septum and connect the two coronary arteries. Survival is related to the extent of collateral circulation from the RCA. About 10 % of patients with ALCAPA have good collateral flow and do not develop early myocardial ischemia as infants. The clinical presentation is delayed until adolescence or early adulthood. In neonates, the symptoms include interrupted crying, diaphoresis, and poor weight gain. In older children symptoms can range from shortness of breath to chest pain especially after any stress or Valsalva maneuver. Signs can be those of heart failure, tachycardia, angina, murmur, and cardiomegaly (Zheng et al. 2011).

ARCAPA is usually asymptomatic and is typically diagnosed when performing other cardiac surgeries or during autopsy. If the patient has a right dominant coronary system with lack of inter coronary system, ARCAPA may present as an infarction, often associated with other congenital anomalies like tetralogy of Fallot and aortopulmonary window (Vairo et al. 1992).

In AAOCA, the abnormal coronary originates opposite from the sinus of Valsalva (right or left). AAOCA is usually asymptomatic in infancy, and symptoms develop with exertion in adolescence and/or adulthood if there is a specific anatomic substrate. Risk factors for developing ischemia include an intramural segment, interarterial segment (between the aorta and pulmonary trunk), acute angle at take-off, and/or ostial stenosis. Early atherosclerosis can develop in these patients. There are several variants: the abnormal left coronary from the right aortic sinus (ALCA-R), abnormal right coronary artery from the left aortic sinus (ARCA-L), and abnormal left anterior descending from the right aortic sinus (ALAD) (Fig. 31.2b, c). In Davies et al. series of AAOCA, ALCA-R (58 %) was more common than ARCA-L (36 %). The abnormal vessel can take an interarterial (between the aorta and the pulmonary artery), retroaortic, prepulmonic, or septal (subpulmonic) course. The interarterial course though rare (5 %) is most frequently seen in patients with ALCA-R and has the highest risk for SCD during exercise. The mechanism for SCD involves coronary ostium stenosis and/or coronary artery compression leading to myocardial ischemia and ventricular tachycardia/ventricular fibrillation. During exercise the myocardial oxygen demand increases, but the supply cannot be met. The increased pressure in the cardiac chamber and/or the great vessels compresses the interarterial segment. Following the law of Laplace (tension = pressure × radius), smaller coronary vessels are at the highest risk of compression from the great vessels (Shriki et al. 2012; Erez et al. 2006; Davies et al. 2009).

This anomaly can present as a consequence in failure to develop or failure to canalize the left main trunk. Most of the time, this absence is compensated by collateral circulation from branches of the RCA.

Myocardial bridges are characterized by coronaries that run in the deeper layers of the myocardium producing ischemia, infarction, or arrhythmias.

These are abnormal connections between coronary arteries and abnormal connections between coronary arteries and cardiac chambers. Most of the time (>50 %), these patients are asymptomatic, but a few can develop congestive heart failure, cardiac enlargement, arrhythmias, obstruction of veins in the right or left side of the heart, “steal” causing ischemia, angina, infective endocarditis, atherosclerosis or thrombosis, and embolization. Frequently patients with pulmonary atresia with an intact ventricular septum have fistulous communication (30–60 %). In patients who associate coronary ostium stenosis, the coronary circulation depends on the RV pressures, and the entity is known as right ventricle-dependent coronary circulation (RVDCC). Patients with RVDCC are at the highest risk for cardiac arrest with induction of anesthesia, because of reduction on RV pressures, coronary perfusion is reduced (Powell et al. 2000; Brown et al. 2006).