The thallium scan helps determine if areas of the heart do not receive enough blood. The exercise thallium scan is especially useful in diagnosing coronary artery disease, the presence of blockages in the coronary arteries (the vessels that supply oxygen-rich blood to the heart muscle).
Yes, it would be appropriate to take a stress test to determine if there are any vessel occlusions that may be blocking a good and adequate blood supply to the heart cells. If there are any occlusions that would strongly indicate the source of your wife's symptoms.
Hope that answers your question, and if you have any other questions, you are welcome to respond. Thanks for your question, take care