How deadly is leg bypass surgery due to peripheral arterial disease?

Small risk: As with all surgery, there is some risk. Your exact risk will depend on your comorbidities.

Heart Risk: The lion share of the mortality risk with leg bypasses is from complications related to your heart. Because we know there are blockages in the arteries of the legs, we presume there are significant blockages in the arteries feeding the heart as well. Your vascular surgeon would likely have sent you for heart testing and found that you were an acceptable risk. Discuss with him or her.

Not especially: The consequences of peripheral arterial disease are extremely serious -- gangrene and osteomyelitis can kill you, slowly and painfully. There are risks with all surgery, and graft infections can be very serious. If medication and lifestyle changes have not successfully cleared your arteries, it's probably worth the risk for most folks. Best wishes, and choose wisely.