Heart Of The Matter: Triathlon Champion Karsten Madsen Triumphs Over Atrial Fibrillation
Education and Advocacy It was the worst night of my life,” remembers Karsten Madsen, a 24-year-old Canadian triathlon champion from Cambridge, Ontario. In his last year of high school, during a fitness test, the student athlete could not run a lap around the gym without panting.

He couldn’t catch his breath.
He knew something wasn’t right and had a hunch it might be atrial fibrillation, a condition involving irregular heart rhythm — something he was familiar with since his dad also had it. Madsen landed in the hospital where his suspicion was confirmed. He joined approximately 350,000 other Canadians who also faced an increased risk of stroke three to five times greater than someone without it and a decrease of cardio output of 30–40 percent. That kind of loss was significant, especially to someone with hopes of becoming a top athlete.
"At night, I’d listen to my heartbeat intently and I couldn’t fall asleep because I was worrying.” Without proper rest, his training suffered and Madsen became depressed.
It was devastating news. “The emergency on-call physician told me I would not be able to race ever again,” he says. “At that point, I was already competing in triathlons in the elite class. I remember lying in the hospital bed — stressed and crying. My heart was peaking at 220 beats per minutes, then dropping to 50.”
The quest for effective treatment
When the therapies prescribed to try and regulate his heartbeat didn’t work, it looked like Madsen would have to be on blood thinners for the rest of his life, precluding him from a future as an athlete. His parents pushed for another option — a cardioversion, a procedure that uses electricity to jolt the heart out of fibrillation and into a normal rhythm. It had worked for his father and Madsen was hopeful it could for him too.
He was lucky. The cardioversion worked the first time. Sometimes, it can take multiple tries. “After that, I was better, not in the rhythm anymore, but I had to go back to training. At night, I’d listen to my heartbeat intently and I couldn’t fall asleep because I was worrying.” Without proper rest, his training suffered and Madsen became depressed.
“I was done,” he says. “Mentally I couldn’t bring myself to train or push myself the way I did before the procedure.” Around the end of 2011, he quit and enrolled in college to become a police officer instead. Part way through the semester, Madsen realized he wasn’t ready to give up his dream of becoming a world-class athlete.
Back on the competitive track
Working with a sports doctor and a coach, he grew stronger — mentally and physically — over time. Every time he did a workout and didn’t experience atrial fibrillation it felt like a victory and his confidence grew. He was back on track.
Fast forward to 2015. Madsen became the ITU National Xterra Champion. Now, he’s setting his sights on the ITU Multisport World Championship taking place in Penticton in 2017. In the meantime, he shares his story about atrial fibrillation — hoping to inspire, support, and encourage others.
“Athletes like Mario Lemieux and Larry Bird also had that condition,” he says. “They’ve had the same issue yet were still able to become top athletes. You just have to be smart about it. Accept whatever comes and know that you’ll be able to deal with it.”