The actor appeared on The Doctors on Wednesday to promote his new NBC show Heartbeat, and he broke some 35-year-old news.
"Ever since I was 10 years old, I was diagnosed with congenital heart block," he said. "Then when I was 14 I got a pace maker put in."
The news shocked Dr. Kathy Magliato, whose life inspired Heartbeat: "I had no idea," she told Kennedy, 45. "You can't even see it."
Kennedy stars alongside Melissa George and Dave Annable in the medical drama about the personal and professional life of heart transplant surgeon, Alex Panttiere.
"I always tell people I learn more on this show than I did in school," Kennedy said of the show, calling Magliato a "legend."
He added, "Each week we have a case that's based on something really bananas."
Heartbeat airs Wednesdays (8 p.m. ET) on NBC; The Doctors airs weekdays (check local listings).