I had quadruple bypass in Jan 2018 at age 56. My symptoms were occasional lightheadedness, out of breath while climbing stairs and occasional tingling in my left arm. Thankfully I did not have a heart attack and I was in reasonable shape from riding 100+ miles a week. Surgery was uneventful and only the chest cracking was painful for several weeks. Once I convinced the cardiologist that I just wanted to get back in the bike he okayed me to skip cardiac rehab. I was biking 37 days after surgery and back to my 100 miles a week a month later. I wear a HRM and have an avg HR in the 120s after a 25 mile ride. I watch my HR above 140 and top out at 160. Just keep riding.