Heart failure with preserved ejection fraction and potential pulmonary hypertension

I'm 19F. With all of my symptoms(shortness of breath, pitting edema in legs rsvp of 42 ejection fraction of 72), my cardiologist did all the tests and diagnosed me with heart fialure with preserved ejection fraction. She also referred me to a pulmonologist who now is sending me in for a right heart catheterization for possible pulmonary hypertension. And pulmonary hypertension freaks me out, because it's fatal. I know I shouldn't be worrying before I know what it is, but I just feel so overwhelmed. Can someone please help explain these things to me?