3 1/2 hours!
When I had mine, I was inpatient and wasn't stable so they used a drug to get my heart to do what it would do had I been able to do a regular stress test (I think it was called andosine or something like that). First, they took images of my heart. Then I did get on the treadmill for a couple of minutes while they injected the drug (not fun) and then they took more images of my heart.
One thing to keep in mind: Stress tests are accurate in women only 80% of the time. They have just recently come to the realization that heart disease presents differently in men then it does in women. Even though heart disease is just as prevalent in women as it is in men, women only make up 25% of study participants. They've always just assumed that the tests used on men will work on women the same. They're realizing now that they were wrong.
In my case, I had a false positive. After the stress test they did a heart cath (my third) and found everything to be ok.
Good luck to you!