What is Vagal overdrive??

Have you tried looking under vasovagal overdrive? Isn't it to do with when vagal activity is decreased and causes bradycardia? Atropine acts to inhibit that... Hahaha, i'm not a med student that's for sure. I'm a vet tech who would much rather have gone and finished her vet degree and constantly trying to diagnose things! I hate not knowing the whys of medicine!!!