Hi, I Was Diagnosed With Rheumatic Heart Disease-moderate Atrial Enlargement

Hi, I was diagnosed with Rheumatic Heart Disease-moderate atrial enlargement with moderate mitral stenosis after returning from a trip to Colorado. this was 6 months ago-I flew back this weekend in the Denver area and experienced after 3 days there-dizziness-inability to speak normally-I do not remember the last day there. Would I have a problem with altitude with Mitral Stenosis?