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EDUCATION EXHIBIT |
1 Department of Diagnostic Radiology, University of Maryland School of Medicine Baltimore, Maryland
Coronary artery anomalies are uncommon but potentially lethal variants that occur in about 1% of individuals (1). Many of this heterogeneous group of congenital abnormalities consist of slight alterations in the normal configuration of the coronary arteries and have no clinical significance. The more important abnormalities are those in which the coronary artery originates or courses in an anomalous fashion. In some anomalies, the origin and course of the coronary artery are both abnormal. Abnormal coronary artery termination, such as occurs with arteriovenous fistula, is often included in the spectrum of coronary artery anomalies (2).
Even among those patients with markedly anomalous coronary arteries, the majority are asymptomatic. Symptoms are often age dependent. In infants, an anomalous origin of the left main coronary artery from the main pulmonary artery may manifest with symptoms of cardiac ischemia because of the perfusion of cardiac muscle by unoxygenated blood from the right side of the heart. Other symptoms with variable age of onset include congestive heart failure due to arteriovenous fistulas and angina pectoris due to myocardial bridging (2).
In young adults, passage of an anomalous coronary artery, particularly the left main or anterior descending artery, interarterially between the aorta and pulmonary artery is associated with sudden death, often during exercise (3). In contrast, a benign clinical course is associated with passage of the anomalous coronary artery anterior to the pulmonary artery, posterior to the aorta, or through the muscular septum.
One proposed mechanism for the mortality associated with passage of the anomalous vessel between the aorta and pulmonary artery is increased tone in the great vessels during physical exertion, causing compression of the intervascular coronary artery (3). Ancillary factors may include the presence of a slit-like coronary orifice and substantial angulation or kinking of the intervascular coronary vessel with respect to its origin, thereby decreasing peak blood flow. The importance of the interarterial form of anomalous coronary arteries is underscored by the fact that this anomaly is the second most common cause of sudden death due to structural heart disease in young adults (4). As a consequence, many investigators recommend prophylactic coronary artery bypass grafting distal to the affected segment as treatment for interarterial coronary arteries, particularly left main and anterior descending vessels (5).
The majority of coronary anomalies are found incidentally at coronary angiography in patients who undergo the procedure for evaluation of coronary artery stenosis. Multiple approaches have been suggested to determine the course of the anomalous artery with respect to the great vessels (6). Nevertheless, a precise characterization often remains elusive because the anomalous artery, the aorta, and the pulmonary artery do not enhance simultaneously. The rarity of anomalies contributes to the lack of certainty among all but the most experienced angiographers (7). Thus, further delineation of the anomaly with noninvasive techniques to confirm or exclude an interarterial course is often desirable. Magnetic resonance (MR) angiography and CT are most often performed.
MR angiography can be used to assess coronary artery anomalies effectively without ionizing radiation or iodinated contrast material. Several investigators have achieved promising results with this technique (8,9). Nevertheless, MR angiography has inferior spatial resolution and is more sensitive to arrhythmias compared with CT, and it cannot be used in patients with cardiac pacemakers.
CT has been shown to be effective in assessing the origin and course of anomalous coronary arteries, initially with the use of electron beam CT (10). More recently, technologic advances have allowed the use of multi–detector row CT for multiple cardiac applications, including assessment of atherosclerotic coronary disease. Investigations have shown multi–detector row CT to have considerable potential for revolutionizing the evaluation of coronary artery stenosis, but substantial challenges remain (11). In contrast, as shown by recent investigations, multi–detector row CT appears poised to assume the role of the standard of reference for the assessment of coronary artery anomalies (12,13).
The article by Kim et al (14) provides a thorough review of the various types of coronary artery anomalies as visualized at multi–detector row CT. The authors’ classification system, based on a modification of an earlier scheme described by Greenberg et al (15), appropriately categorizes anomalies by origin, course, and termination. In addition to the high-quality multi–detector row CT scans of coronary artery anomalies, many correlative conventional angiograms are provided.
To date, the most common clinical indication for the use of noninvasive imaging (including multi–detector row CT) in variant coronary artery anatomy has been the assessment of suspected anomalies discovered at catheter-based angiography. In this context, multi–detector row CT appears to have recently gained the ascendancy over other noninvasive techniques. A more far-reaching consideration is the likelihood that increasing use of gated CT for a variety of cardiovascular studies, such as assessment of the aorta and pulmonary vasculature, will lead to large numbers of anomalies being discovered incidentally at multi–detector row CT. The goal for all CT practitioners will be to correctly identify the anomaly, determine its clinical importance, and provide an appropriate follow-up recommendation. The article by Kim et al (14) will undoubtedly serve as an excellent reference for achieving these objectives.
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-year experience at the Texas Heart Institute. Tex Heart Inst J 2002;29:299–307.[Medline]Related Article
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