I don't want to seem pushy but this is a serious matter and absolute truth has to be implemented here.
The best advice is to call emergency services.
My husband had a heart attack while he was alone and the feeling that your heart is working at a different rhythm is nonsense, it doesn't happen like that.

Please, if you or anyone you know is in distress, call emergency services. Don't try to deal with it yourself, you could cause more damage or even death to your 'patient'.

https://www.bhf.org.uk/heart-matters-magazine/medical/ask-the-experts/cough-cpr