What Causes High Heart Rate And Breathlessness, Given My ECG Shows Sinus Tachycardia And My Echo Shows Mild MR, TR, And PAH?

I am 22 year old female with normal BMI. I had echo and ecg done due to high heart rate and shortness of breath on exertion. My ecg shows sinus tachycardia(129bpm). All parameters in my echo are normal except mild MR, mild TR with mild PAH with RVSP 45mmhg. My blood profile is normal including thyroid and hemoglobin. What could be the reason of my high heart rate and shortness of breath?