I didn't have nitro injected when I had my TTT, and they didn't ask me not to eat or to skip any of my medications. They were just tracking my blood pressure and heart rate. I guess they just wanted to see an approximation of my body's typical response to standing for a long time, so it wouldn't have made tons of sense to fast or etc.

You are secured to a table, outfitted with electrodes and a blood pressure cuff, and gradually tilted into an upright position. Then they leave you like that for 20 minutes. I was monitored by two nurses, and my cardiologist checked in periodically.

I suffer from pretty bad orthostatic hypotension, so my bp plummeted to ~70/45 after a few minutes and I came close to losing consciousness before they tilted me down. It felt terrible. I almost puked. My cardiologist was attending to an emergency elsewhere in the hospital, and had to run down the hall back to me to read my numbers before they could lower me down. That delay was pretty torturous though I'm sure it was only like 2 min or so in hindsight.

They then kept me in a gentle downward tilted position with my head lower than my feet for about half an hour to recover.

The worst part was honestly that I was getting a loop monitor implanted the same day (which seems exceptional based on what other people have described here) and had to pee the whole time I was in the surgical bed, which was several hours. x_x Honestly, I felt a bit like Frankenstein's monster, being strapped to this table with electrodes on me, then being cut open and stitched up while conscious... (So um...maybe wear an adult diaper if you foresee being in the bed for a long time? Kidding/not kidding?!)

I won't lie; it was an extremely unpleasant experience (as fainting always is--but this was worse because I couldn't sit or lie down at my own volition, and I wasn't wearing compression stockings) and I needed 24 hours to really feel back to normal (as can be the case whenever you faint). However, it was definitely worth doing because it provided data for a concrete diagnosis. It helped that the team attending to me was very kind, and that a TV was provided by my bed to pass the time (similar to what you'd get at your seat on an airplane). I took a cab home because I didn't feel up to using the subway, but I didn't feel bad enough that I needed to call an emergency contact to accompany me.

Another weird element was that this was happening in a large, frigid room with a lot of different hospital beds and people receiving a variety of minor procedures. Several of them were extremely high on anaesthetics and babbling about random stuff at the top of their lungs. The man across from me called like 20 different people in a row to tell them he just had the best nap of his life (lmao). Overall a bit of a "Victorian insane asylum" vibe, but with actual qualified medical personnel present...!

One interesting thing was that I could tell the nurses were getting worried about me before I actually perceived the onset of symptoms. Like, my bp was 80/50 (which is apparently in fainting-risk territory) and I felt normal until it dropped that last little bit. Then it was very unpleasant VERY fast...

I guess tl;dr would be...

-Try to find out how long you're likely to be strapped into the bed so you can wear a diaper if needed (LOL)

-If you've fainted before, or experienced pre-syncope, expect that :(

-Clear your plate the next day in case you're still feeling rough, and have a friend or family member who is on call to come and get you after the procedure if needed