It's not talking about blocked arteries, it's stating regenerating the damage to a heart post heart attack / cardiac arrest. Once heart muscle is damaged from MI heart attack or prolonged arrest due to lack of oxygen, that muscle is dead.
No shit, that's what I just stated. What the article is stating is MRNA may be able to regenerate the dead tissue. The post I replied to apparently didn't even skim the article, due to their reply to that post. Still a big no thanks to the MRNA on that one or any for that matter