text: how do they perform a 4 1/2 hour cardio stress test? i am scheduled to have this stress test next week. i can't figure out why it takes so long to perform. i am a nuclear medicine technologist.  and i think you are talking about a cardiac stress imaging test.  i don't know exactly how the facility you are doing it at does their's, there's several ways to do it.  i am assuming it is the rest/stress method.  so, what they will do is inject you with a radioisotope while you are at rest, wait about 20 minutes and image your heart for about 15 minutes or so.  then you come back in about 1-2 hours and they will run you on the treadmill to reach your target heart rate, once in is reached, they will inject a radioisotope again while your heart is in a stress state.  they will put you on the camera again and image your heart for 15-20 minutes.  this time they will hook up some ekg leads to synchronize your heartbeat with the camera.      the purpose of imaging your heart in a rest and stress state is to find spots where the radioactive medicine didn't perfuse to in the heart muscle.  when you exercise the coronary arteries dialate and blood usually perfuses to the heart muscle better.  now if the pictures show an area where there was no perfusion on rest and stress images, that means that is dead muscle that cannot be repaired by increasing perfusion to the muscle, it probably died when you had a heart attack or some chest pain over time.  but if the images show a area that didn't perfuse on rest, but then it did get blood to it when you exercised and opened up those coronary vessels, then it is fixable.  they will probably put in a stent and/or do blood thinner therapy to get blood to that heart muscle so it doesn't die.