For mRNA vaccines to cause change in your DNA, it needs to integrate with your DNA. For doing so it needs to pass through the cells nucleus (which it cannot do as it requires certain signal molecules) then it needs to convert into DNA via reverse transcriptase (which it doesn’t have) and then integrate into your DNA via integrase enzyme (which it lacks). So vaccines can’t change your DNA that’s for sure. 
But rise in heart related issues after COVID has much to do with lockdowns more than vaccines according to me. Lockdowns caused increase in fear, stress, sedentary lifestyle and at the end of the day we are social beings and are not made to be locked inside a house. 
I might sound blue pilled 😂 but that’s what I believe is true.