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J Thorac Cardiovasc Surg 1996;112:836-840
© 1996 Mosby, Inc.

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CORONARY ARTERIES ARISING FROM THE CONTRALATERAL AORTIC SINUS: ELECTRON BEAM COMPUTED TOMOGRAPHIC DEMONSTRATION OF THE INITIAL COURSE OF THE ARTERY WITH RESPECT TO THE AORTA AND THE RIGHT VENTRICULAR OUTFLOW TRACT

Paris, France

Received for publication Dec. 7, 1995 Accepted for publication Feb. 29, 1996. Address for reprints: Elie Mousseaux, MD, PhD, Service de Radiologie Cardiovasculaire, Hôpital Broussais, 96 rue Didot, 75014 Paris, France.

The variations in the initial course of a coronary artery with an abnormal origin are more important than the abnormal origin itself. Certain of these variations are associated with sudden death, myocardial infarction, or angina pectoris when the left main coronary artery or the right coronary artery passes between the aorta and the pulmonary trunk. ¹ The relationship between the initial course of the aberrant coronary artery and the aorta and the right ventricular outflow tract, however, can be difficult to assess by coronary angiography. Electron beam computed tomography (EBCT) and magnetic resonance imaging have recently shown potential in the visualization of the coronary arteries. ^2,3 This report describes six cases in which the initial courses of the left main coronary artery, originating in the right sinus of Valsalva, or the right coronary artery, originating from the left sinus, were clearly detailed with EBCT.

Case histories and EBCT results

In three cases with the left main coronary artery arising from the right aortic sinus, EBCT detected the initial course of the abnormal coronary artery with respect to the right ventricular outflow tract. The passage of the artery between the aorta and the pulmonary trunk was found in one patient admitted to intensive care for an extensive acute anterior myocardial infarction (Fig. 1). Coronary arteriography showed the left main coronary artery arising from the initial part of the right coronary artery in the second case. EBCT examination (Fig. 2) depicted the intramyocardial tunneling of the left main coronary artery within the septum before its bifurcation into the left anterior descending and circumflex arteries. In the third patient with an extremely abnormal left ventricular compliance (Fig. 3), the course between the pulmonary artery and the ascending aorta could not be formally ruled out by conventional coronary arteriography. The passage of the left main coronary artery well in front of the pulmonary trunk was clearly detected by EBCT. EBCT confirmed the right coronary artery's origin in the left aortic sinus and detected the passage of the artery between the pulmonary artery and the aorta in three other cases (Fig. 4).

View larger version (570K): [in this window] [in a new window]   Fig. 1. Electrocardiographically gated 100 msec axial EBCT images after enhancement at four levels from top (A) to bottom (D). Both exact origin of left main coronary artery (arrow) from right sinus of Valsalva and its passage between ascending aorta (AA) and pulmonary artery (PA) are shown in A and B. Division of left coronary artery into left anterior descending and circumflex arteries behind pulmonary artery is depicted in B, C, and D.

View larger version (698K): [in this window] [in a new window]   Fig. 2. Electrocardiographically gated 100 msec axial EBCT images after enhancement at four levels from top (A) to bottom (D). Left coronary artery arises from initial part of right coronary artery (arrow) in B, C, and D. Its intramyocardial course crossing upper part of interventricular septum is shown in C and D (open arrow). A also shows calcified left anterior descending artery and circumflex artery lying within anterior interventricular groove.

View larger version (505K): [in this window] [in a new window]   Fig. 3. Two native electrocardiographically gated 100 msec axial EBCT images after enhancement at two levels in A and B. C, Three-dimensional surface-shaded image. D, Selective right coronary arteriography viewed in left anterior oblique projection. Origin of left coronary artery (black arrow) from right coronary artery (white arrow) in right sinus of Valsalva is seen in A and B. Initial course of left coronary artery in front of pulmonary artery (PA) is shown in C and D; it then divides into left anterior descending artery (white arrowheads) and circumflex artery (black arrowheads). AA, Ascending aorta.

View larger version (129K): [in this window] [in a new window]   Fig. 4. Electrocardiographically gated 100 msec axial EBCT images after enhancement. Both coronary origins are detected on left aortic sinus, and the passage of right coronary artery (arrow) is detected between ascending aorta (AA) and pulmonary artery (PA)

This report illustrates the utility of EBCT in determining the exact origin of the left main coronary artery from the right sinus of Valsalva, or the right coronary artery from the left sinus of Valsalva. Above all, it shows that this method is accurate for evaluating the initial course of the abnormal coronary artery with respect to the right ventricular outflow tract. The passage of the artery between the aorta and the pulmonary trunk, considered an important risk factor for infarction or sudden death, can be diagnosed by this means. When the left main coronary artery arises from the right aortic sinus or the right coronary artery arises from the left sinus, it can be difficult to determine angiographically whether the aberrant vessel passes in front of the right ventricular outflow tract or behind it, between the outflow tract and the aorta. In our experience, the best way to determine this has been to pass a catheter into the main pulmonary artery and then perform an arteriogram of the aberrant coronary artery in the direct lateral projection. The catheter locates the pulmonary artery, and it is then usually possible to determine whether the coronary artery runs anterior or posterior to the outflow tract. Invasive procedures during coronary arteriography can be avoided, however, if EBCT is employed after conventional arteriography.

Selective coronary angiograms may also be difficult when the origin of the coronary artery is abnormal. This was the case in two patients in our study in whom the right coronary artery arose from the left sinus of Valsalva. EBCT was nevertheless able to detect the abnormal origin of the right coronary artery in these patients and show that it ran between the pulmonary artery and the aorta. The intramyocardial tunneling illustrated in Fig. 2 is the second important variation in course of the left coronary artery arising from either the aorta or the common coronary artery that can be recognized by EBCT. Detection of such variation can alter management, because the absence of evidence of myocardial ischemia, both clinically and at autopsy in reported cases, suggests that tunneling is unlikely to cause myocardial ischemia. ⁴

EBCT is based on scanning electron beam technology that eliminates all mechanical motion except for that of the patient table. The EBCT scanner acquires complete computed tomographic scans in 50 or 100 msec, producing high-resolution images free of artifacts even in moving organs such as the heart. In this study, EBCT was therefore carried out with contiguous electrocardiographically gated 100 msec scans during breath holding and delivery of an injection of 100 ml contrast medium. A distance between sections of 3 mm or less ensures that the initial few centimeters of the coronary arteries and their relationship with the neighboring structures at the base of the heart can be visualized. The minimum section thickness with the new systems of EBCT is 1.5 mm, and this should allow better three-dimensional representation of coronary arteries. ³ Morphologic EBCT analysis was carried out on the native sections and after three-dimensional reconstruction and surface-shaded representation, such as in Fig. 3 (C).

EBCT was initially developed for the noninvasive quantification of coronary calcium, ⁵ but these new systems of both acquisition and representation may well make it capable of detecting atheromatous coronary stenoses by the injection of contrast material. ³ Charges for heart EBCT examination with intravenous contrast medium in the United States currently range from $600 to $800. The diagnosis of coronary stenosis by tomographic methods has already been shown to be feasible with magnetic resonance angiography without the need for contrast material and ionizing radiation. Both spatial resolution and coronary artery enhancement, however, are still less than those obtained by EBCT during breath holding.

Acknowledgments

We thank Lynn Sartori and Owen Parkes for their editorial assistance.

Footnotes

From the Department of Cardiovascular Radiology,^a INSERM U66,^b and the Department of Cardiology,^c Hôpital Broussais, Paris, France.

References

1. Roberts W. Major anomalies of coronary arterial origin seen in adulthood. Am Heart J 1986;111:941-63.[Medline]
   
2. Manning WJ, Li W, Boyle NG, Edelman RR. Fat-suppressed breath-hold magnetic resonance coronary angiography. Circulation 1993;87:94-104.[Abstract/Free Full Text]
   
3. Moshage WE, Achenbach S, Seese B, Bachmann K, Kirchgeorg M. Coronary artery stenoses: three-dimensional imaging with electrocardiographically triggered, contrast agent-enhanced, electron-beam CT. Radiology 1995;196:707-14.[Abstract/Free Full Text]
   
4. Roberts W, Dicicco B, Waller B, Kishel J, McManus B, Dawson S, et al. Origin of the left main from the right coronary artery or from the right sinus with intramyocardial tunneling to the left side: the case against clinical significance of myocardial bridge or coronary tunnel. Am Heart J 1982;104:303-5.[Medline]
   
5. Fallavollita JA, Brody AS, Bunnell IL, Kumar K, Canty JM. Fast computed tomography detection of coronary calcification in the diagnosis of coronary artery disease. Circulation 1994;89:285-90.[Abstract/Free Full Text]
   

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