you should keep something with you at all times in case of emergency. either bracelet, necklace, or info inside your wallet. better someplace to be easily seen my emergency personnel!
Being a red cross certified life guard and CPR and first aid, if we decide you need shocked with the machine that get your heart going, we’d need to know that before we used it on you. It would kill you if we did it and you have a pacemaker.
So yes if you accidentally pass out and quit breathing and need shocked to start your heart others need to know this so they can perform the right life saving technique. Make sure you wear something to let other know, they don’t always have time to search med. record.