About 20% of adults who have major non-cardiac surgery had elevated troponin levels, yet nearly all of them did not have symptoms of injury, according to a new scientific statement from the American Heart Association. People with cardiovascular risk factors such as high blood pressure and type 2 diabetes, as well as those with sleep apnea, anemia, congestive heart failure or who are older than age 75 should be monitored for elevated heart enzymes after surgery to improve outcomes, according to the new statement published today in Circulation journal.