I have gone through the same issue. Mine was caused by strep throat oddly enough. The infection moved from my throat to the lining around my heart causing it to swell and damage my heart. Doctors were initially confused because this is something that is extremely uncommon nowadays (It was common in the 30's/40's and is still around in less fortunate parts of the world). It shows and reacts like a heart attack. I was instructed to take a month off work and light duty the second month and back at it after that. I can understand being a high level athlete being instructed to take more time off. Not sure how severe his is but it's never fun, I lost 20-30% of my heart function but have since fully recovered so my hopes are high for Letestu.