I have done this test, and I work in a facility where we do these exams on a daily basis. There are two different ways that this can be done. There is a "stress" portion done on one day, and the "resting" portion done on a different day. In our facility we can do either one first. For each of the two days there are two parts. In one type of the test you will walk on a treadmill to reach a target heart rate, and for those that are not able for physical or other reasons are not able to do a treadmill there is a medication to simulate exercise. The stress portion of the exam in our facility is done with a doctor present. I had no after effect, and rarely see any adverse effect from anyone who has had this exam. It is a good tool to learn what the heart is doing or no doing. As with any type of exam your doctor is the best place to get information regarding any potential issues you may have.