In his last year of high school, during a routine fitness test, Madsen could not complete a lap around the gym without panting. Later that evening, he was diagnosed with atrial fibrillation, otherwise known as AFib, a heart condition that results in a 30 percent loss of cardiac output.

“At that point, I was already competing in triathlons in the elite class,” Karsten recalls. “I remember lying in the hospital bed, stressed and crying. My heart was peaking at 220 beats per minutes, then dropping to 50.”

Pulse points

According to the American Heart Association, more than 2.7 million suffer from atrial fibrillation in the U.S., which heightens risk of future heart disease, blood clots and stroke. The most common symptoms include irregular and rapid heartbeat, palpitations, dizziness and shortness of breath.

When seeking treatment, Madsen’s parents opted for 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, who also lives with the condition, and Madsen was hopeful it could work for him too.

'“At night, I’d listen to my heartbeat intently and I couldn’t fall asleep because I was worrying.”'

He was lucky. The cardioversion worked the first time. But it wasn’t an immediate return-to-form.

“At night, I’d listen to my heartbeat intently and I couldn’t fall asleep because I was worrying,” says Madsen. Without proper rest, his training suffered and he became depressed. But in a moment of clarity, Karsten changed his outlook and decided to not abandon his dreams.

A new perspective

“There are people who have it far worse than I do all over the world,” he explains. “My worst-case scenario is kind of like breaking an arm, except when you break an arm, you need six weeks to recover. For me, I can go into the hospital and be cardioverted with a deliberator and I’m ready to go again with no lag.”

When training, the sportsman has to monitor his heart rhythms carefully. “I do a lot of counting beats, especially when the intensity is high,” Madsen outlines. “I truly believe that my AFib is triggered by large amounts of stress. I just have to make sure I’m taking deep breaths and that I have a little bit of time each day to unplug and turn off.”

Staying the course

In 2015, Madsen became the ITU National Xterra Champion. Today his sights are set on the ‘ITU Multisport World Championship taking place in Penticton, Canada in 2017. In the meantime, he shares his experiences with AFib, hoping to inspire, support and encourage others.

Madsen lives in Ontario, where he works with community programs to help youth stay active. His advice for patients who may have been recently diagnosed? “Just keep plugging with it — don’t let it change what your goals are.

"You can still be an athlete; you just need to be mindful. Athletes like Mario Lemieux and Larry Bird also had that condition,” he offers. “It actually makes you more in tune with your body, and teaches you what to listen for.”