I've heard that before, I wouldn't think that's really out of the question. It's not just heartbeats though, depending on the sport, it's the wear and tear of other parts of the body too. Marvelous Marvin Hagler looked like the picture of health and he died at about 68, which is 6 years short of the average person. No cause of death was ever given. Joe Louis and Sugar Ray Robinson, about as great as fighters get, both died in their late 60's too. Joe had heart problems, he also got involved in drugs at a ridiculous older age. Sugar Ray had diabetes and pugilistica dementia, they both had brain problems. Joe was put into a psychiatric facility at one point by his son.
You'd think athletes would live longer lives but they die just like everyone else at about the same ages, even earlier depending on the sport.