Help needed with a plothole: can vampires 'make' their hearts beat?

So, I'm writing a story about a girl discovering a supernatural world parallel to her own. The twist is, the ordinary world has been shocked by the discovery of vampires, and they're being hunted down and put into 'reserves'.
Every student and every working person has to undergo a bi-annual 'MediCheck', where they basically check if you're human. I've found ways for my vampires to evade things like a blood test and a body temperature test (including them spreading rumors about themselves so they can easily pass other normal vampire 'marks', like not being able to be seen in a mirror). Anyway, I've just discovered a huuuuge plothole: vampires' hearts don't beat.
In 'my' mythology, blood sort of kick-starts the vampire's body again: the blood flows, albeit very slowly, the blood enables a vampire to heal and use their supernatural abilities, even lets their hair and nails grow again (albeit very, very slowly), and most importantly, let them control the muscles of their body. So would it be too implausible to give them control over the muscles of their hearts, so they could make their heart beat by choice, like they can breathe by choice but it's not necessary?