Aortic Aneurysms & Dissections

A) True aneurysm

Outpouching or dilatation of all three layers of the heart

Fusiform:

—spindle shaped expansion of the entire circumference

—involvement of the entire circumference of the artery

—most common type

Saccular:

—outpouching involving one side of the artery

§ Whether fusiform or saccular, the lumen of the aneurysm characteristically contains laminated clot

§ Many aneurysms are not pure examples of either. By the time the aortic wall has been stretched to aneurysmal size, little or no recognisable aortic tissue is present. The wall is composed entirely of fibrous tissue

B) False aneurysm

a pulsating haematoma; a disruption in the arterial wall allows an accumulation of blood to be held in place by the surrounding tissue

C) Dissecting aneurysm

§ occurs when blood between the medial and intimal layers of the arterial wall begins to split the arterial layers; can lead to rupture of the artery

D) Aortic Dissection

§ Longitudinal cleavage of the aortic media by a dissecting haematoma is the cardinal feature of aortic dissection

§ The medial separation is not usually circumferential, but the entire length of the vessel is often involved

§ Plane of dissection:

1. Ascending aortalateral margin of aorta
2. Archsuperior aspect [greater curvature]
3. Descendingoften lateral; may be medial or spiral

§ An intimal tear connects the true aortic lumen with the false lumen

§ The tears are usually single & transverse

§ Ascending aorta is involved in two-thirds of all aortic dissections — the intimal (“entry”) tear is usually located a few cm above the aortic valve; the medial dissection may confine to the ascending aorta but usually extends beyond the arch

§ Dissections limited to the descending aorta constitute 25% of all cases and are the 2nd more frequent anatomical type; here the proximal limit [associated with the entry tear] is near the left subclavian artery

DeBakey Type I	Stanford Type A Daily	Diffuse lesion of aorta that includes ascending aorta, aortic arch & descending aorta
DeBakey Type II	Stanford Type A	Lesion only involves proximal and transverse aorta [small group]
DeBakey Type III	Stanford Type B	Lesion involving aorta distal to left subclavian