Case report:
A 36-year-old athletic male mountain biker with no significant past medical or cardiac history suffered from upper respiratory symptoms 6 weeks before hospital admission. He had a positive test by polymerase chain reaction (PCR) for COVID-19 infection at that time. The patient had received the second dose of the Moderna vaccine at the end of May 2021. Two months later, he suffered from severe fatigue and persistent bradycardia at the time of his positive COVID-19 testing with a heart rate (HR) in the 30s. He was diagnosed with a breakthrough COVID-19 infection.  His symptoms gradually improved but his exercise tolerance remained very limited and he could not raise his heart rate appropriately with activities. Due to persistent fatigue and bradycardia, he went to urgent care where he denied any significant dizziness or syncope.