The Wrestler/WMG

The final frames are...

 * . The entire movie is about him losing everything but wrestling.  His heart is then trying to take that away from him, too.  The final match is even with his rival from his peak.  His heart starts failing near the end of the match, but he does his big finishing move anyway.  From a medical perspective, it's inevitable.  From a storytelling perspective, it's poetic.
 * That's not really a guess so much as heavily implied.