Vieussens' Arterial Ring.

The Vieussens' artery is an anastomotic communication between the conus branch of the right coronary artery and the left anterior descending (LAD). Vieussens' ring is so named because it circles around the great vessels in the form of a partial ring. The course of the artery can be best understood in 2 orthogonal views. In the left oblique view, the artery appears coursing upward to the left. In the right oblique view, it courses anteriorly across the right ventricular outflow tract. The clinical significance of Vieussens' arterial ring lies in it being a major source of collateral blood flow to an occluded LAD. The presence of this large collateral may explain preserved ventricular function in our patient, despite severe triple-vessel disease.