Sam Champion admits he was caught off guard when he learned he’d have to undergo an emergency heart procedure this week.

On Monday, the “Good Morning America” weathercaster took many viewers by surprise when he shared a photo of himself on Instagram in a hospital bed. In the accompanying caption, he thanked medical professionals at Mount Sinai’s Fuster Heart Hospital in New York, while noting he was “expected to make a full recovery” following the procedure.

Returning to “Good Morning America” on Wednesday, Champion spoke candidly about the procedure, which he said took just one hour to complete. Though he’d been tested repeatedly, he said, his doctors had told him “everything looked fine” until they took note of one symptom.

Watch Champion speak about his health below.

“I’m healthy. My heart presents as healthy,” he explained. “There was one symptom that kept persisting. I didn’t know it could mean a heart attack until I had a nuclear stress test to see what was going on inside my heart, to see how my heart was moving and holding blood.”