Hi there ~
Having had or having a myocardial infarction
is not something that you should disregard, especially when you also have heart palpitations. Though medical marijuana has been approved for chronic intractable pain
in certain states of the united states of america, it is not yet in use or FDA approved for anxiety
or palpitations. You should also get yourself tested for the palpitations and get treatment for the same. It is critical that your friend stop marijuana use now, and that marijuana use probably increases the risk of any cardiovascular disease
though there is not much in terms of scientific research that has been conducted on it due to industry pressures.
I hope this helps and hope your friend comes off of marijuana and finds different and adaptive ways of having fun and relax. Take care and have a lovely day !