12years ago I had a six cab.recently on a walk I felt a burning in my chest. I had a catherizatin done one found the arter that goes on the left side of my heart is totally blocked and can't be repaired. They increased my atenenol and isorbiride but I am afraid to do emptying for fear of a heart attack. Someone told me this is called a widow maker. Can I exercise I was walking on a treadmill for 3 miles and doing it in 40 minutes gradually going from 3 mph to 4 mph and changing incline positions from o to 12. Now at 2.6 mph and 13 minutes I get a burning in my chest and calves.