Should I have my 11 year old Shar Pei treated for heartworms?

I have an 11 1/2 year old Shar Pei. Two nights ago a pitbull broke into our yard and did a lot of damage to my dog before we could rescue him. He went to the vet and has around 100 stitches all over his body. The worse part is that I found out he has heartworms. What is the life expectancy of a Shar Pei and should I put him through the pain of the treatment?