Angel Vazquez, 38, of Kissimmee, Florida, vividly remembers the moment last June when he first thought he was having a heart attack. He was working from home that day—his mom was there to take care of his daughters—when suddenly he started to feel terrible. “I started to sweat profusely, I had trouble breathing, my heart was pounding, and I felt like I was about to faint,” he tells Runner’s World. “I didn’t want to freak anyone out, but I just had a gut feeling. My dad had two heart attacks and my uncle had a few as well.” So he...