Are you seeing a cardiologist and/or peri?
Did you know you had mitral valve prolapse already? Pregnancy puts a much greater load on your heart because your blood volume increases so much, so what might have been a minor prolapse can become much more significant.
My understanding is that when your heart is not functioning well (e.g. the mitral valve problems) it has to work harder, and so it beats faster. It's also not uncommon to have irregular heartbeat in this situation.
I was not diagnosed until about 34 weeks, and my twins ended up being born a few days later. By that time, I was in congestive heart failure, so they treated me pretty aggressively. I did take a beta blocker, along with digoxin, which also regulates the heart rate.
I really think that if your heart rate is that high, you have to do something to lower and regulate it. I would also be concerned that your heart function should be monitored pretty closely, so that you can be treated appropriately if it starts to get worse (which sometimes happens as the pregnancy advances because your blood volume increases). Another thing that was stressed by my docs was that it's important to have it under good control before you have to deal with labor (although that was fine for me, as it turned out).
If your doctor said, basically, there was nothing he/she could do, you have to see another doctor.
I hope that doesn't sound too blunt. The thing is, cardiac problems in pregnancy are relatively rare, and so most OBs don't see them often. But it is nothing to mess around with. You should obviously watch closely for signs of swelling (which my OB and I brushed off as normal...not) and shortness of breath (which I assumed was asthma...not).
Good luck, and feel free to post again or email me off-list if I can be of more help.
Nancy
