Greg Welch's Heart

Former world champion triathlete and "world's fittest human" Greg Welch has survived nine open-heart surgeries in the past 2 1/2 years. He's only 40 years old and is the father of two young girls. Welch suffers from ventricular tachycardia (V-tach), which makes his heart beat dangerously fast.

"My bad days are behind me," says Welch, who had a defibrillator implanted. "They're over. ... I'm the luckiest man in the world."