FIG 3. Example of aneurysm formation, with persistent stenosis (group I-C 6-mm elliptical defect).

A, Angiogram shows a double shadow due to a massive adventitial hematoma that formed immediately after lesion creation.

B, Angiogram obtained 2 hours later shows a subadventitial hematoma with the characteristics of an aneurysmal pouch.

C, Angiogram obtained 1 week later shows that the hematoma has become a saccular aneurysm.

D, Chronic-stage (3-month) angiogram shows that the aneurysm is smaller.

E, Photograph shows external protrusion of the aneurysm (arrow).

F, Chronic-stage photograph obtained in shows that part of the intimal defect extends to the aneurysm orifice (arrow).

G, Chronic-stage photomicrograph shows that the inner layer of the aneurysm dome (asterisk) is covered with organized clots and fully endothelialized (elastica van Gieson stain, original magnification x5). Arrows indicate the adventitia; single arrowheads, media; double arrowheads, intima.

H, Scanning electron micrograph shows endothelialization (original magnification x700).