I am 48 years old with only a Hx of MS. I tried my 1st dose of Tysabri in November and had an allergic reaction and they stopped the med and gave me Benaddryl and steroids. Since I am very lightheaded, SOB and have chest pain. I can not tolerate any activity. My Neuro says it is Cardiac. I had a Chest CT that just shows some minor plaque, my echo only show a Tricuspid Valve leak mild- mod. I had a nuclear stress test that made me lightheaded, SOB and gave me some chest pain. The results show my heart rate accelerates to fast, there is poor Cardiac perfusion in one section of the heart and Aortic enlargement. A Cardiac Cath is recommended, what do you think it may show, and what kind of tx is needed. I know I need this test, but I am frightened to do it. I really don t have a choice as I can not tolerate any activities. Need some advice, or what to ask the Drs.