Who needs an ambulance when you can actually run to the hospital? That's exactly what one man did. His is a story of surprise and survival. A marathon runner in seemingly perfect health having a heart attack. And believe it or not, doctors say the sport itself may actually alter heart health.

His medals are just one symbol of his years as an endurance athlete, triathlons, the ironman, marathons. But this image may better reflect the toll so much exercise has taken on Richard Doran's body. The 46-year old had 100-percent blockage in a coronary artery.

Dr. Justin Levisay, Clinical Cardiologist, NorthShore University Health System: "And he actually walked into the Evanston emergency room during his run, they did an EKG and found he was having a heart attack."

Richard Doran, 46-yr-old marathon runner and heart patient: "That day I was set to do a 17 mile run."

Like other marathon runners in the home stretch of training, Richard felt good as he embarked on the long run.

Richard Doran: "It was about an hour and 20 minutes into the run, and I felt fantastic. I was doing 8:15's, 8:30's, my heart beat was right, felt good. And then all of the sudden, out of the blue I got a sudden feeling of indigestion."

Instead of pushing through like so many athletes – ignoring pain, this father thought of his family listened to his body. Though weak, he sprang into action.

Richard Doran: "And I just decided, I just said to myself, 'This is not my time.' And I started walking towards the hospital. I was only four blocks, thank God."

Dr. Levisay: "I looked at the EKG, and without question he was having a heart attack. When you see this whole area of the heart that's not getting blood supply after 3-5 minutes this heart muscle actually starts to die."

It's happened before during races – but often occurs even in training as athletes drive themselves further. Running long distances actually alters the blood.

Dr. Levisay: "The blood becomes sticky, the heart is working harder, there's just a whole host of hormones and responses for your body to exercise, which are a good adaptation to exercise, however, in terms of the cardio vascular system they can absolutely cause problems and the risk is even greater when you're actively running."

The very exercise that *does* improve heart function, in extremes can change the heart muscle.

Dr. Levisay: "There is a danger to extreme endurance athletics. There was a study done in Britain and what they found is that 50 percent of the people who had done all of these marathons or were endurance athletes their whole lives had scarring of their heart. And that zero percent of the people who didn't had scarring of the heart.

Heavy exertion causes inflammation … a buzzword for heart attack.

Dr. Levisay: "That high levels of inflammation in your body are associated with the development of coronary artery disease.

Richard Doran: "Anything to an extreme can't be that good, but when you do feel like you're in great shape, you just kind of do it, its normal it's a normal part of your life."

Richard learned the hard way. But he has the rest of his life to spend with his family appreciating his health now.

Richard Doran: "Even if you have some signs and you don't think its anything major, its not a bad thing to go get it checked out. Because if you don't get it checked out and something major does happen, you know there's no dead heroes. Thank God I'm here."

Doctors say while they want people to know the dangers of extreme athletics and the new research showing the permanent damage to the heart, exercise itself is good for you. The epidemic of heart disease in this country is not caused by people being too active, it's from people not being active enough.