Though Allison Longest had a normal pregnancy, soon after she gave birth to her son, Zachary, on December 16, 2013, she and her husband noticed that something was wrong. “He wasn’t eating very well, and after looking into it, the doctors at Riley Hospital for Children at Indiana University Health discovered that he had a heart murmur,” the 39-year-old from Indianapolis told Runner’s World. “But it was minor, and no one was that worried about it.” Two weeks later, Zachary was brought in for a heart check-up on Christmas Eve. To the surprise of his parents, the doctors diagnosed him...