Anomalous aortic origin of the coronary artery with an interarterial course (AAOCA) is a relatively rare congenital cardiac defect that is associated with increased risk of sudden death and cardiac morbidity (Fig. 32.1). Presentation of AAOCA in adulthood
is most commonly associated with symptoms of coronary ischemia and/or arrhythmia. Most common symptoms include dyspnea with exertion, chest pain at rest or with exertion, atrial or ventricular arrhythmia, syncope or near syncope, and sudden cardiac death. The combined incidence of these defects approximates 0.17% in autopsy series and 0.1% to 0.3% in patients undergoing catheterization or echocardiography. In a postmortem study, 57% of the 49 patients with anomalous origin of left main coronary artery (ALMCA) and 25% of those with anomalous origin of right coronary artery (ARCA), died suddenly. Increased risk of sudden death associated with exercise is well described with both ALMCA and ARCA, but sudden cardiac deaths may occur in asymptomatic patients and without predisposing exercise. In the older adult patient, the defect may exist alone or on combination with atherosclerotic coronary disease. It is difficult to define the risk of death or serious complications related to this defect but estimates by Mirichandani places risk of death due to anomalous interarterial coronary artery at 1/650 and Corrado puts risk at 24 per 100,000 person-years.

In this anomaly, the anomalous artery originates in the wrong sinus and travels within the wall (intramural) of the aorta to exit the aorta adjacent to the appropriate sinus. The coronary passes between the aorta and the pulmonary artery. While most of these anomalous coronary arteries are intramural and interarterial, some may be extramural and interarterial. This variant is still considered at risk because of the potential compression between the aorta and pulmonary artery and sudden death is reported in both clinical and pathologic series.

The potential mechanisms responsible for ischemia and sudden death with AAOCA is displacement of the intimal flap covering the ostia of the coronary artery into the lumen of the artery during diastole, compression of the interarterial portion of the coronary artery during systole, and during exercise with higher pressure in both
the aorta and pulmonary artery, spasm, or compression of the anomalous coronary within the intramural segment by the intercoronary commissure. In the adult patient, the diagnosis is sometimes made serendipitously during provocative testing for other cardiovascular disease with catheterization or echocardiography.

Because of the risk of sudden death and other adverse cardiac events, most cardiologists and surgeons recommend surgical repair of AAOCA ALMCA especially with symptoms, or evidence of, ischemia on provocative testing. Controversy exists regarding management of the AAOCA ARCA. Most, but not all, cardiologists recommend surgical repair for the symptomatic ARCA patient, but there has been increasing reluctance to recommend surgery for the asymptomatic patient with ARCA because of the relatively low risk of sudden death in this patient population especially in the young (<10 years) and the older (>30 years). Also, morphologic characteristics of the AAOCA do not seem to predict risk of adverse outcome; making decision for surgical intervention even more difficult. The small risk of sudden death or cardiac ischemia must be weighed against the risk of the operation. Unfortunately, even though the mortality and morbidity is minimal with current surgical therapy, the long-term outcome of the manipulated coronary artery is yet to be determined. If surgical repair is declined or deferred, avoidance of strenuous physical activity and competitive athletics is often prescribed, but is not necessarily protective because in athletes who had sudden cardiac death, more than half had a negative stress test.

Still, some cardiologists believe that the risk of sudden death with the asymptomatic ARCA is so small, that exercise limitation is not necessary. Until there is some rational consensus or data-driven treatment algorithm regarding the nonoperative management, there will continue to be controversy and consternation by patients and practitioners alike.

Anomalous origin of the left coronary artery from the PA is very rare in adults. Most patients present in infancy with severe heart failure and mitral valve insufficiency. As the pulmonary vascular resistance falls in the neonate or infant, coronary blood flow is syphoned away from the myocardium into the low-pressure pulmonary circulation, resulting in myocardial ischemia dilated left ventricle and mitral valve insufficiency. If the pulmonary vascular resistance remains high or there is high pressure in the pulmonary artery for other reasons like peripheral pulmonary stenosis or high RV pressure from a large VSD, then there is less runoff of coronary flow into the pulmonary artery and myocardial perfusion is preserved. In this situation, the defect may go unnoticed until adulthood and only be discovered during investigation for other cardiac problems, usually with echocardiogram or CT scan. Indication for repair of this defect is usually upon diagnosis as long as there is not significant cardiac dysfunction or complicating factors like suprasystemic pulmonary hypertension. In most cases, associated cardiac defects like mitral valve disease, pulmonary stenosis, and the presence of pulmonary hypertension make perioperative care very complex.

Patients with ALCAPA whose coronary collateral system is well developed in infancy may survive into adulthood without developing symptoms. However, the blood fllig;ow in the left coronary becomes retrograde and preferentially fllig;ows into the pulmonary artery (coronary steal) resulting in signi filig;cant myocardial ischemia unless there is significant pulmonary hypertension to prevent a steal situation. All adults with this defect are at risk of sudden death without surgical revascularization. More than 90% of patients who survive into adulthood will die at a mean age of 35 years without surgery.

ARCAPA is more likely to be associated with other congenital heart defects and less likely to present in infancy. In fact, 50% of the patients with this lesion are asymptomatic at presentation. Thus the defect may have a higher prevalence than thought. Like ALCAPA, if symptoms are present they are likely to be CHF. AV valve insufficiency is unusual. Repair of ALCAPA or ARCAPA is to establish a two coronary artery system by translocating the anomalous coronary to the aorta, and is indicated at the time of diagnosis.

The significance of myocardial bridging has been a topic of controversy. Myocardial bridging is defilig;ned as a segment of a major epicardial coronary artery, which travels intramural through the myocardium beneath the muscle bridge. Myocardial bridging is generally confined to the mid left anterior descending artery (LAD) greater than 70%. The degree of coronary obstruction by the myocardial bridge depends on such factors as location, depth, length of the muscle bridge, and degree of cardiac contractility. The estimated frequency that has been reported varies from 1.5% to 16% when assessed by coronary angiography, but in some autopsy series, it is as high as 80%. Angiographically, the maximal decrease in luminal diameter within the myocardial bridge during systole was 84% at rest, with a persistent decrease in diastolic diameter of 41%. Traditionally, myocardial bridging has been considered a benign condition, however, presentation and symptoms include: Ischemia and acute coronary syndromes, coronary spasm, ventricular septal rupture, arrhythmias (including supraventricular tachycardia and ventricular tachycardia), exercise-induced atrioventricular conduction block, stunning, transient ventricular dysfunction, early death after cardiac transplantation, and sudden death.

Ischemia associated with the myocardial bridge may result in gross or microscopic changes such as interstitial fibrosis, replacement fibrosis, contraction-band necrosis, or increased vascular density. The depth of the coronary artery under the epicardium may predict the severity of pathology and risk of sudden death and may be helpful in the decision to intervene.

Normally, only 15% of coronary blood flow occurs during systole. Angiographically, the maximal decrease in luminal diameter within the myocardial bridge during systole was 84% at rest as noted above, with a persistent decrease in diastolic diameter of 41%. It has been postulated that the repeated compression of the intramyocardial coronary may result in increase sheer stress on the intima just proximal to the intramyocardial portion and eventually result in fixed narrowing or atherosclerotic changes. Atherosclerotic changes rarely affect the coronary artery under the muscle bridge. Indication for repair of these defects is the presence of symptoms or in association with other cardiac surgical repair.

Coronary artery fistulas result from the abnormal termination of the coronary artery. Coronary artery fistulas are estimated to be present in 0.2% to 2% of the population and may be even more prevalent. Congenital coronary artery fistula formation is attributed to the persistence of abnormal sinusoidal connections to cardiac structures from the coronary arteries. Coronary fistulae can involve connection to a cardiac chamber (coronary–cameral fistula) or to a central venous structure (coronary arteriovenous fistula). Most patients who experience symptoms related to a coronary artery fistula present during the fourth through sixth decades of life. In adults, they are usually congenital, but may be acquired as when associated with trauma or after a cardiac surgery. Most are single but may be multiple and may arise from both coronary arterial systems. They originate most commonly from the LAD and second most from the RCA and usually terminate in the pulmonary artery and the right atrium or ventricle. As these are low-pressure chambers, flow through the coronary artery will gradually increase and because the fistulous communication is usually quite small, the pressure combined with the increased flow in the coronary will result in dilation of the proximal coronary. It is thought that some fistulas spontaneously close in childhood, but some persist into adulthood and the coronary artery can become quite dilated and the left-to-right shunt can result in significant CHF. Ischemia may result from a steal of blood into the low-pressure chamber through the fistula. Endarteritis of the fistula has been reported. The dilation of the coronary can be quite significant and alarming, but rupture is exceedingly uncommon. Adult patients with coronary artery fistula usually have a continuous loud murmur and cardiomegaly on x-ray. They often have an abnormal ECG,
even though they are unlikely to have symptoms of ischemia. They are most likely to have congestive heart failure from the left-to-right shunt.

Therapy is indicated in all symptomatic patients. Percutaneous device closure has become the first-line therapy whenever possible.