Case Presentation. A 52-year-old veteran presented to the emergency department with typical angina. In the hospital, myocardial infarction was ruled out and a myocardial perfusion scan was performed for evaluation of reversible ischemia. The myocardial perfusion scan showed a moderate postero-basal area with mild reversibility. A gated pool study estimated the ejection fraction to

Figure 1

Right coronary angiogram showing occluded right coronary artery in its proximal segment and Vieussens artery draining into the Aneurysmal Sac. CA 1 = communicating artery number one; Catheter = right coronary diagnostic catheter, JR4; RCA = right coronary artery.

be 47%. The patient underwent cardiac catheterization. Right coronary angiography (Figure 1) showed a completely occluded right coronary artery in its proximal course. Contrast injection of the right coronary artery also filled another artery originating from the superior aspect of right coronary artery known as the Vieussens’ artery1 or the right conus artery (Figure 1). The Vieussens’ artery divided into two channels that reconstituted to form one communicating

Figure 2

Aneurysmal sac communicating with pulmonary artery at the junction of communicating artery number two and the sac. Contrast washout is seen in the pulmonary artery. CA 2 = communicating artery number two; CA 3 = communicating artery number three; LM = left main artery; LAD = left anterior descending artery; LC = left circumflex artery; Catheter = left coronary diagnostic catheter, JL4.

artery that drained into an aneurysmal sac (Figure 1). This aneurysmal sac was also fed by another two communicating arteries that arose from the left coronary system, as noted on the left coronary angiogram (Figure 2). One of the communicating arteries arose from the left main artery at its origin and had a tortuous course before terminating in the aneurysmal sac. The other communicating artery arose from the diagonal artery and also terminated in the same aneurysmal sac. The aneurysmal sac itself measured 1.7 x 1.0 cm. The left coronary artery angiogram also revealed a left anterior descending artery with moderate stenosis in the proximal segment and a high grade lesion in the mid portion (Figure 2). There was a large left circumflex artery with a high-grade ostial lesion of the second marginal. On further examination of the coronary angiogram, it was noted that the aneurysmal sac had a communication to the pulmonary artery, and the injected contrast was seen washing away in the pulmonary trunk (Figure 2) during the left coronary angiogram. Right heart catheterization did not find any significant step-up of the patient’s oxygen saturation.

When the Vieussens’ artery forms an anastomosis with a similar arterial branch from the left coronary system and occasionally with the pulmonary trunk, it is called the Vieussens’ arterial ring.2,3 This is the first reported case of aneurysm of this arterial ring system. This case also presents a unique form of left-to-right shunt that includes both the right and left coronary systems. Vieussens’ arterial ring was first described by Raymond de Vieussens1 in 1706. It is thought to be a remnant of embryonic cono-truncal circle that gives rise to coronary ostia. Its clinical significance is unknown, but is proposed to serve as a collateral between the right and left coronary arteries in the event of an ostial right coronary artery, an ostial left main or a proximal left anterior descending artery occlusion.3