“Vieussens ring”- an unusual form of inter-coronary collateral from conus artery to diagonal artery

In patients with critical stenosis or total occlusion of either the left anterior descending artery or right coronary artery, the conus branch of right coronary artery sometimes serves as a major source of inter-coronary collateral. These collateral channels form the Vieussens ring. Here we report a case of a 74-year-old diabetic and hypertensive male whose angiogram revealed normal appearing left main, discrete lesion with critical stenosis of proximal left circumflex (LCx), left anterior descending artery (LAD) revealing diffuse disease of mid segment with critical stenosis and dissection, and chronic total occlusion of right coronary artery. However, diagonal branch could not be visualized. The large and tortuous conal branch was filling the large diagonal branch of LAD. In our case, Vieussens ring was serving as collateral to diagonal branch instead of LAD. It has both diagnostic, as well as therapeutic implication as it helps surgeon to avoid any inadvertent damage to the conus artery especially if surgery involves manipulation of the right infundibulum. It may serve as an alternative to the retrograde route when the lesion cannot be successfully crossed using an anterograde approach for LAD recanalization.