Inappropriate Sinus Tachycardia

Does anyone have (IST) Inappropriate Sinus Tachycardia? I'm 19 weeks and 5 days pregnant and went to see a Cardoligist today because of my heart rate being way to high and haveing spells of getting dizzy and very hot and sweaty and almost passing out. Just wondering if anyone has this or something like it and what did they do for you?