Advertisement It was a cold, clear night in Melbourne on May 20 as Kate Bendall lay rugged-up in bed reading her Kindle. But something felt off. She woke her husband Simon and told him she was having palpitations. “It felt like there was a horse race going on in my chest,” the 50-year-old nurse said. “It felt scary.” Simon sat up and noticed his wife looked pale. He tried taking the pulse on her wrist, but struggled to locate it. He remembered that his Apple watch had recently been updated with an ECG app, so he gave the watch to Kate. Using the feature they were able to measure the rhythm and strength of her heart’s electrical signals.