Chemical Treadmill

I had to take a treadmill test today for a pre-surgical cardiac workup. Because it's a hip replacement, I couldn't do the regular "trot till you drop" routine. No worries. They lay you out, inject some kind of poison into your vein, and for six minutes you wish you were dead. The drug expands your arteries (?), simulating the effects of a murderous run. There's a cardiologist right there "in case", but it's the nurses who notice you've turned beet red. "Are you uncomfortable?" After what seems like half an hour, they cheerfully announce: "You're almost halfway through...only a little more than three minutes."I assume surgery is still a "go". Surely they'd have called by now if something turned up. ...Oops, there goes the phone.