Cold induced coronary artery vasospasm is very real. A deep breath in the severe cold whilst exercising gets freezing air down the trachea and into the bronchi producing reflex coronary artery vasospasm.
I thought this was medical hype until about 6 years ago (age 54) when i went up a hill in sub zero temperatures before warming up. i suddenly realised what crushing central chest pain was!
Stoped the bike and put a scarf over my mouth to prewar the breath and it settled in a moment o but I was properly scared and never doubted it again