It would take a very large dose to affect the heart and even then it would just lead to a slower heart rate instead of stopping it. The heart does not need nerves to tell it to beat and it’s action potential triggering is different than muscles and nerves. They’ll be brain dead from being without oxygen before they’re heart dead, similar to opioid overdoses.
I would personally imagine that you may need to be defibrillated at some point but otherwise probably yes? The toxins are causing the paralysis and people do survive it so I can only imagine that the heart takes back over after a certain amount of effort. Otherwise, I don’t actually know.