Imaging Studies
For initial screening purposes, preferred imaging modalities should (1) be noninvasive; (2) be applicable to a wide population, at a reasonable cost, with a minimal level of side effects such as those that could be involved in the use of ionizing radiation; and (3) have reliable diagnostic accuracy.
Noninvasive imaging modalities in patients with coronary artery anomaly are used to either visualize the anomalous vessels or evaluate a heart murmur or symptoms of dyspnea, angina, syncope, or endocarditis. Visualization of anomalous coronary arteries can be achieved by the following noninvasive methods:
Transthoracic and transesophageal echocardiography
Echocardiography is an attractive screening option in view of its relative simplicity, noninvasiveness, lack of ionizing radiation, relatively low cost, and widespread availability. [25, 26] However, the discriminating power of echocardiography is intrinsically limited (both temporally and geometrically), and few opportunities are available for aligning the echocardiographic imaging planes with the coronary anatomy, which presents curves and phasic movements. Therefore, this technology is less than ideal for firmly diagnosing most types of coronary artery anomalies in adults.
Computed tomographic angiography (CT angio)
For studying coronary artery anomalies, CT angio has seen a dramatic rise in interest since the introduction of multidetector computed tomography (MDCT) scanners with 4 detector rows in 1998. The earliest reports on coronary artery anomalies were based on experience with electron-beam computed tomographic (EBCT) scanning, which correlated closely with coronary angiography. [27, 28, 29, 30]
Initial reports concerning the use of MDCT for identifying and characterizing anomalies of coronary origin and course have been quite encouraging, especially considering the benefits of 3-dimensional image reconstruction. [31, 32, 33, 34] Multiple MDCT studies of coronary artery anomalies have already been performed, including studies done to correlate noninvasive findings with that of invasive coronary angiography. Rapid advances in CT angio technology has made this imaging modality a reliable means of defining coronary artery anomalies. However, routine use of CT angio in young patients with suspected coronary anomaly should be discouraged due to exposure to relatively high doses of ionizing radiation. The importance of interpretation skills and proper training in accurate diagnosis of coronary artery anomalies by this modality should be emphasized.
Coronary magnetic resonance angiography (MRA)
MRA is a noninvasive technique without the disadvantages of CT angio, including ionizing radiation and nephrotoxic contrast agent. As a tomographic imaging technique, MRA allows 3-dimensional reconstruction and omnidirectional visualization of a coronary artery origin and course. In several published series, MRA has been shown to be as accurate as coronary angiography in defining the origin and proximal course of the coronary arteries. [30, 35, 36, 37, 38, 39, 40, 41, 42, 43] However, high resolution definition of the more distal portions of anomalous coronary arteries may be problematic in some patients.
Although generally considered safe, MRA is not free of limitations including its inability to be used in patients with claustrophobia or in those with certain metallic implanted devices. Gadolinium-based MR contrast agents have also been implicated in several instances of nephrogenic systemic sclerosis, particularly inpatients with advanced kidney disease.
This modality of imaging is, however, the preferred diagnostic test in younger patients in whom echocardiography has failed to provide adequate definition of the coronary artery anatomy.
Invasive coronary angiography
Definitive diagnosis of coronary artery anomalies at times requires selective arterial angiography via catheterization. [44]
During coronary angiography, placing a pulmonary artery flotation (Swan-Ganz) catheter to guide assessment of the course of the anomalous vessels is recommended.
Origin of coronary artery from pulmonary trunk may require pulmonary angiography; however, most arteries are visualized during selective arteriography of vessels originating from the aorta.
Other Tests
Other diagnostic studies include the following:
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Electrocardiogram (ECG) for evaluation of myocardial ischemia. Note that congenital coronary artery anomalies associated with the origin of the left main or right coronary arteries from the opposite sinus of Valsalva and the type B (ie, between the aorta and pulmonary trunk) course of the anomalous vessel are of particular concern in young competitive athletes. Standard testing with ECG under resting or exercise conditions is unlikely to provide clinical evidence of myocardial ischemia and is not a reliable screening test in athletes. Premonitory cardiac symptoms may occur shortly before sudden death (typically associated with anomalous left main coronary artery), suggesting that a history of exertional syncope or chest pain requires exclusion of this anomaly.
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Nuclear myocardial perfusion studies using exercise and single-photon emission computed tomography (SPECT) in association with thallium or technetium-based radiolabeled agents can demonstrate ischemia within the myocardial territory supplied by the anomalous coronary artery. Coronary angiography is then recommended to define coronary anatomy.
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Intracoronary ultrasonography: This invasive study allows evaluation of the mural structure of anomalous coronary arteries in patients in whom invasive coronary angiography fails to clearly demonstrate degree of luminal narrowing or its physiologic significance.
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Coronary angiography showing separate origin of the left anterior descending (LAD) and left circumflex (LCx) coronary arteries from the left coronary sinus of the aorta (absent left main).
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Coronary angiography showing the anomalous origin of the left main (LM) coronary artery from proximal right coronary artery (RCA) with subsequent retroaortic (dorsal [type D]) course to the left side.
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Selective left coronary artery angiogram demonstrating anomalous origin of obtuse marginal (OM) coronary artery from proximal left anterior descending (LAD) coronary artery. LM=left main, LCx=left circumflex.
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Coronary angiography showing the anomalous origin of the right coronary artery (RCA) from the left anterior descending (LAD) coronary artery with subsequent anterior course (anterior [type A]) to the right atrioventricular groove.
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Coronary angiography showing the origin of the right coronary artery (RCA) as the continuation of the left circumflex (LCx) coronary artery.
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Coronary angiography showing the presence of a fistula originating from a diagonal (diag) branch of the left anterior descending coronary artery with anomalous communication with the pulmonary artery (PA).
