Unexplained tachycardia episode

I'm a 31 yo female, 5'4", 155 lbs. I was experiencing tachycardia during my first pregnancy 4 years ago, had a full cardiac work up and while the tachy was attributed to increased blood flow due to pregnancy, I was diagnosed with a benign 1st degree AV block. Fast forward to second pregnancy (delivered April 08) and had similar tachycardia episodes. No big deal.

This week, I woke up feeling nauseous in the middle of the night, threw up once, felt dizzy and nauseous all the next day and after almost passing out, went to ER. My heart rate was up as high as 155. After tons of blood work, EKG's, echocardiagram and 3 bags of IV fluids, they basically had no explanation as to why my hr was so high. It stayed in the 130-140 range for 16 hours. In the end the doc said may have been a combination of a virus, stress, exhaustion, etc.

Is this an acceptable thing to have happen while not pregnant? Do I need to have more extensive cardiac work-ups to determine if there is an underlying cause for this? What are the other differential diagnosis possibilities for this type of thing? Thank you so much!

[Michael J. McWilliams, M.D.]

I always think back to right after my wife and I got married.  She got the flew and her heart rate stayed around 130-140 for about 3-4 days.  If you are very sick, your heart rate can easily go that high.  If an EKG was done and the rhythm was sinus tachycardia --- normal rhythm, must fast -- that means your heart is responding to physiologic stimuli (pain, fever, fear, etc).  Some people have a higher resting heart rate and there heart rates increase faster than others.

The first place for you to start is with your primary care doctor.  If they think it is appropriate for further cardiac testing, they will order it.