Heart rate problems while being pregnant

So out of curiosity has anyone experienced a high heart rate while being pregnant? I am 33 weeks and 4 days and yesterday my heart rate went up to 170 and my baby girls heart rate dropped tremendously! I almost passed out, my ears were ringing, I couldn't see anything, and I ended up throwing up because of it! It got to the point where they were going to do an emergency C-section but luckily my heart rate and baby's heart rate both went back to normal. I just had to get an echo done on my heart today and I am having to wear a heart monitor for 24 hours because they do not know what has caused this! I was just wondering if anyone has experienced anything like this during their pregnancy and what did you have to do? Were you able to deliver the baby still naturally or did you have to have a C-section?