What are the effects of an electric shock on the heart?

I have a friend who told me 6 months ago he received an electric shock at work of 4000 volts, which is extremely high. he went into cardiac arrest, but his work mates performed cpr and got him back, then took him to the hospital. at the hospital they told him he was ok, but he was supposed to get heaps of tests done afterwards, as the shock was so big. he told me he never got the tests done, as they cost so much and he felt fine. but he also said his heart sometimes has like murmurs or extra beats or something? im pretty sure theres a proper word for it. do you think he needs to get the tests done? or will they be a waste of time and money? could there be any life-threatening permanent damage done? thanks guys