Wow! welcome to the forum. That is a pretty complicated procedure although certainly doable.
1) You would have to isolated the cardiomyocytes carefully.
This would entail looking up Pubmed to see what previous investigators did to extract viable cardiomyocytes.
Q: Do you really need cardiomyocytes carefully extracted? Or can you simply remove the heart and simply extract the proteins from whole tissue?
2) Protein extraction is quite easy once you got the cells. You could easily extact with a proteomics compatible lysis buffer. Dialyze the cells and get them ready in a buffer that allows 2-D separation. Hard part is going to be getting SAME amount of protein loaded for DISEASE heart failure cells and Normal cells.
3) Separate on 2-D. Get a fun robot to collect the spots. Send them all in for sequencing! and compare using scanning/sequencing CONTROL vs DISEASE!
hope that helps!
post here your response!