During sudden cardiac arrest — which is caused when the heart's electrical system suddenly malfunctions — the heart stops beating and blood is no longer pumping through the body or the brain. Harper probably survived the event because of his excellent physical fitness and the immediate medical attention.However, the fact that he was in such terrific shape also made having a heart attack at 51 that much more stunning.(Photo by Bennett Raglin/Getty Images for The Valentine Fuster Mount Sinai Foundation for Science, Health & Empowerment, Inc.)NEW YORK, NY - APRIL 17: Bob Harper poses at the opening night of the new musical based on the film 'Groundhog Day' on Broadway at The August Wilson Theatre on April 17, 2017 in New York City.(Photo by Bruce Glikas/Bruce Glikas/Film Magic)Bob Harper attends the Hetrick-Martin Institute's 30th Annual Emery Awards: Help Me Imagine at Cipriani Wall Street on December 7, 2016 in New York City.(Photo by Jared Siskin/Patrick Mc Mullan via Getty Images) Kohl's Wellness Ambassadors Kevin Curry, Jordan Younger and Bob Harper attend the Kohl's Motivation Market on January 12, 2017 in Los Angeles, California.(Photo by John Sciulli/Getty Images for Kohl's) TV personality Bob Harper poses for a portrait during the NBCUniversal Press Day at The Langham Huntington, Pasadena on January 13, 2016 in Pasadena, California.
(Photo by Andrew Toth/Getty Images)NEW YORK, NY - NOVEMBER 07: Bob Harper attends The 2017 ICP spotlights luncheon honoring Pulitzer Prize-Winning photojournalist Lynsey Addario on November 7, 2017 in New York City.(Photo by Thos Robinson/Getty Images for the International Center of Photography)NEW YORK, NY - APRIL 24: Host Bob Harper during the Tribeca Film Festival premiere for the feature documentary, The Resilient Heart, at the Tribeca Film Center on April 24, 2017 in New York City. Valentin Fuster on his global trek to fight heart disease by educating adults as well as todays new generation on how basic lifestyle changes can have a significant impact on your health.The film was directed by Oscarï¿½-nominee and Grammyï¿½ winning director Susan Froemke, and was made with generous support from The Valentin Fuster Mount Sinai Foundation for Science, Health & Empowerment, Inc.More than 326,000 people suffer an out-of-the-hospital sudden cardiac arrest each year, according to the American Heart Association.The survival is an estimated 10 percent, although that may increase to about 30 percent if treated quickly with a defibrillator, as Harper was.