As someone who experienced heart attack like symptoms as an under 30 year old, did go into the hospital and got a pericarditis[1] diagnosis, I think that describing your friends unknown heart condition as a heart attack is unnecessary fear mongering considering similar symptoms can present themselves as a much less severe condition. Both the Vaccine and Covid are known have a low chance of causing heart issues.

[1]https://www.mayoclinic.org/diseases-conditions/pericarditis/....