What Causes Double Vision, Vertigo And TIA Like Symptoms?

I get double vision and vertigo-like symptoms.. one doctor suggested transient ischemic attacks.. i dont have risk factors like diabetes or high blood pressure.. instead i have bradycardia (during the day 35bpm, at night drops below 30bpm). i usually have the problems when i have to get up and moving around really quickly in the mornings. the mornings i can take it slow getting up and dont have to rush anywhere i tend to be more likely to be okay. can the heart have trouble going from 30bpm while sleeping to 60+bpm while im rushing around if it has to increase too quickly? if it does, would it not get enough blood/oxygen to my brain causing symptoms like TIA? ive seen a neurologist who had me get an mri to rule out brain tumor. ive seen a cardiologist several years ago for othostatic hypotension, which i dont have nearly as often as i used to.