The near-passing out quite possibly had more to do with your bearing down than your
PVCs. I wish I could remember the URL for it, but I just saw a funny video where I get pressed a heavy barbell over his head. It was obviously more than he was used to. The muscles tensed to make that lift are a lot of the same ones you used to bear down.
After the lift he dropped the barbell, took two steps, then fell flat on his face. Unconscious. There are times when after a meal, if I'm on the floor reading my kids a story, I'll stand up quick and need to hold onto something.
It's just the body reacting to inputs, opening up arteries and veins, reducing blood pressure really quickly, which can cause you to pass out.
And think of the breathing/stethoscope thing the doctor always does, that we were talking about recently - it almost always gets me close to passing out, and it does to most others, too.