Anomalous Course of the Left Main or Left Anterior Descending Coronary Artery Originating From the Right Sinus of Valsalva
Identification of Four Common Variations by Electron Beam Tomography
An aberrant origin of the left main coronary artery (LM) or left anterior descending coronary artery (LAD) from the right sinus of Valsalva is a rare anomaly that has been associated with myocardial ischemia and sudden cardiac death. Depending on the anatomic relationship of the anomalous vessel to the aorta and the pulmonary trunk, the anomaly can be classified into 4 common courses: posterior, interarterial, anterior, and septal course. Contrast-enhanced electron beam tomography (EBT) has been shown to permit classification of anomalous coronary arteries. We present 4 cases that illustrate the common variations of this anomaly. In all cases, EBT was performed using a C-150 XP EBT scanner (Imatron Inc). During inspiratory breathhold, 40 to 50 axial cross-sections of the heart were acquired triggered to the ECG at 40% of the R-R interval (100 ms acquisition time, slice thickness 3 mm, table feed 2 mm, intravenous injection of 160 mL contrast agent at 4 mL/second). In addition to the original axial images, 2-dimensional multiplanar reconstructions and 3-dimensional reconstructions were rendered on an image processing workstation (NetraMD, ScImage) to display the anatomic course of the anomalous LM or LAD. In all cases, the results were confirmed by invasive coronary angiography.
Posterior or Retroaortic Course
In the nonprocessed axial image (Figure 1A) and the 3-dimensional reconstruction (Figure 1B), EBT shows the retroaortic course of the LM that originates from the right sinus of Valsalva and passes posterior and inferior to the aortic root.
Interarterial or Preaortic Course
Anterior or Prepulmonic Course
In a patient with a right-sided single coronary artery, the LAD originates from the proximal right coronary artery and takes a course anterior to the right ventricular outflow tract to the left anterior interventricular groove (Figures 3A and 3B). The left circumflex coronary artery (LCX) follows a retroaortic course (not displayed).
Septal or Subpulmonic Course
In this case, the LM ostium is located adjacent to the right coronary ostium. The LCX takes a prepulmonic path, whereas the LAD follows an intramyocardial course through the interventricular septum beneath the right ventricular infundibulum (Figure 4A). The artery surfaces in the midsection of the interventricular groove, which is clearly shown in the 3-dimensional reconstruction (Figure 4B).
These examples illustrate the potential of contrast-enhanced EBT to visualize the exact 3-dimensional course of anomalous coronary arteries.
The editor of Images in Cardiovascular Medicine is Hugh A. McAllister, Jr, MD, Chief, Department of Pathology, St.Luke's Episcopal Hospital and Texas Heart Institute, and Clinical Professor of Pathology, University of Texas Medical School and Baylor College of Medicine.
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