Atheromatous changes of blood vessels affects early in -
Sites of Atherosclerosis 

Atherosclerotic plaques develop primarily in elastic arteries (e.g., aorta, carotid and iliac arteries), and large & medium sized muscular arteries (e.g., coronary artery and poplitial arteries).
In descending order, the vessels most commonly involved are -


Abdominal aorta (most common) → Causing aneurysm
Coronary arteries (heart) → Causing MI
Popliteal arteries → Causing ischemic gangrene of lower limbs.
Internal carotid arteries → Causing stroke
Circle of willis → Causing stroke


Vessels usually spared are
Vessels of upper extremities
Mesentric and renal vessels, except at their
Kidney
Liver
Heart
Spleen