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Figure 1 The coronary venous system. Coronary veins parallel the major epicardial coronary arteries, but are free of obstructive disease, and thus can provide a platform for myocardial access. The anterior, septal, and lateral walls are drained by branching vessels from the anterior interventricular coronary vein (AIV) (which parallels the left anterior descending artery), which drains into the great cardiac vein (GCV) (paralleling the left circumflex artery) and through the coronary sinus (CS) into the right atrium. (A) Anterior and (B) posterior views. AIV = anterior interventricular coronary vein; CS = coronary sinus; GCV = great cardiac vein. Courtesy of Transvascular, Inc.