An athlete receives a heart-stopping diagnosis

At age 40, Tania is a keen endurance athlete, participating in competitive triathlon and mountain bike events.
During a routine consultation, she mentions that, while participating in a recent first-aid course, she was observed to have an irregular pulse.
She has also noticed frequent skipped heartbeats in the past few months.
On occasion, she has episodes of breathlessness and visual disturbance during intense exercise.