Saturday, September 29, 2012

Innominate Artery Aneurysm

Speaking of the innominate artery (a.k.a. the "brachiocephalic artery"), what is the likelihood of an innominate artery aneurysm?

Well, the first step would be to know what the normal diameter of the innominate artery is....

The reported normal size of the innominate/brachiocephalic artery is between 8-13 mm with 14 mm or greater considered dilatation.

The patient below is a 71Y lady who presented for evaluation of liver cysts.  During the exam dilatation of the innominate artery to 18 x 18 mm was also found, with dilatation of the origin of the right subclavian artery and kinking of the origin of the right common carotid. Although pacemaker wires were present for sick sinus syndrome, no cardiology report or prior imaging mentioned dilatation of the innominate artery.

71Y F with a right innominate artery/brachiocephalic artery aneurysm and kinking of the right common carotid artery. Incidentally, the diameter of the aorta is top normal at 3.9 cm.

My attempt at a Terrarecon reformat of the aneurysm.  There is artifact at the origin of the innominate and left common carotid artery from the overlying pacer wires in the left brachiocephalic vein.  This angle of view is meant to demonstrate the nondilated origin of the innominate artery corresponding to a class A aneurysm (below).

According to a recent series, innominate artery aneurysms that involve the origin of the artery (B) or involve the ascending aorta (C), are more common than those that only involve the artery itself (A).

Isolated aneurysms of the innominate artery are definitely uncommon events, although there does not seem to be a documented incidence in the literature. Conditions that are considered predisposing risk factors are the usual large artery arteriopathies: Takayasu's arteritis, syphilis, and of course, atherosclerosis.

In the 1950s, most innominate artery aneurysms were due to syphilis and presented at a late stage with compressive symptoms and few interventional options.

The most specific symptoms related to a compressive innominate artery aneurysm include dysphonia, dyspnea, or SVC syndrome.  Dysphonia is related to its proximity to the recurrent right laryngeal nerve, curling around the right subclavian artery (below).

Embolization of aneurysm thrombus material to the right upper extremity and right cerebral hemisphere are other documented sequelae of an innominate artery aneurysm.

Buckling or kinking of the innominate artery implies elongation,  tortuosity, and dilatation of the vessel, but the artery can buckle without being aneurysmal. This differentiation was more of a concern in interpretation of frontal radiographs, before the true size of the vessel lumen could be easily measured with cross-sectional imaging.

Treatment of an innominate artery aneurysm remains surgical.

1. Honig, EI, Steinberg I., Dotter CT. "Innominate artery: angiocardiographic study," Radiology 58: 80, 1952.
2. Honig EI, Dubilier Jr. W, Steinberg I. "Significance of the Buckled Innominate Artery." Ann Intern Med. 1953 Jul;39(1):74-80
3. Kieffer E, Chiche L, Koskas F, Bahnini A. "Aneurysms of the innominate artery: Surgical treatment of 27 patients." Journal of Vascular Surgery 34:2, 2001.