Constriction In Throat, Difficulty Breathing. Upper GI Test, ECG Done. Causes?

I have a friend who is suffering some symptoms and her physicians so far have been able to make a diagnosis. She will suddenly suffer a constriction in the throat and tightness on the right side of her upper torso. She has had to go to emergency twice when her throat closed up and she had difficulty breathing . She has had a upper Gi test and an ECG . I think some blood tests have been done. I think she is going to have an MRI . She is an otherwise very healthy woman of 56 who plays tennis almost every day and is very fit and has a good attitude toward life. She said she doesn t have allergies and hasn t been around any pesticide spraying. We re concerned.