What reasons would a person not be able to have bypass surgery perform on 3 arteries blocked over 90%? patient is 36, 6'1", 200 lbs.

Bypass: There could be medical reason like severe kidney disease , lung disease or due to technical reasons like the vessels are too small.

Usually can: Diffuse distal atherosclerosis and no place to do the hookup. Other would be some life risk or expected short life expectancy. Most can be bypassed. Seek thoracic surgical opinion if not done already. At 36 and not huge, would seem to be worth doing.