I don't pretend to be an expert in this area but getting medical equipment approved is a huge undertaking and I don't know what the ramifications of changing anything would be. Say they take your 0day and fix it. Then they have to go through the entire re-certification process again and after however many months or years, NEW patients get the fixed pacemaker. But what about all the old patients?
While I sympathize, the only realistic approach here is to make the consequences for killing someone via a 0day for the "lulz" so drastic that it would certainly legally bleed over into the disclosure. I realize this is the approach we do tend to take here in the US.