How does DRUGs used 4 calming a heart disease???

Recently i came to know my father've heart disease problem might be older age & workload i couldn't stayed here bit felt bad but he was in treatment after all lots of caring person towards him .......nothing to worry abt them 2,3 days back he got well in normally .... i was wondered it must be reasoned behind nothing else its a "DRUGS". DRUGS are then used to shrink it to a normal size. So, after getting DRUGS heart pump is implanted to give the heart a rest. Once, the heart has gone down in size more DRUGS can be given to strengthen d organ.