Right Axis Deviation???

I am a healthy 25 yo white female. 5' 6" and regularly 140 lbs.   I am an ex-smoker of 6 years (quit Aug 2007).  I just had my second child October 5th of this year, no complications with either pregnancies or births.  I have always had a slight mitral valve murmur.

Last week, I noticed I had some chest pressure at times.  I checked my heart rate and at the times I felt the pressure, my HR was in the 40's.  I had an echo and EKG this past April,  They were both normal other the mild mitral valve regurgitation (MVR).  I went to the doctor this past Friday because of the problems I have been having, and my EKG showed RIght Axis Deviation.  He said the right side of my heart is working harder than the left side. My bloodwork came back normal.  My doctor set me up for a Cardiology appt next week.  

What would cause my EKG to change in those few months?  I am nervouse about what might be wrong.  I am assuming I will have another EKG and maybe an Echo to look further into this situation.  Does anyone have any advice, similar situations or idea of what might be going on?? Thanks.  Good luck to you all.

[itdood]

I don't have particular experience with this.  Wikipedia has good info on it though.  From what I read this can either be very mild or very pronounced.  For mild RAD, they said it was due to things like bing very tall and how the heart sits in the thorax.  For pronounced RAD it's due to a congenital defect in the heart, something usually termed heart block.  For this type of RAD, the heart block occurs in something called the AV node.  One of the branches that stimulates the ventricles doesn't send a signal to that side to beat (hence the block).  This means the stimulation will come around to that side from the other ventricle which causes a delay.  Instead of the ventricles beating at the same time they beat at different times, hence the deviation.  

The only reasons I can think of why it didn't show up until now are.  

It requires a sensitive 12 lead EKG to detect
Other docs missed it
Or, it wasn't always there and just occurred now.  This would mean it's probably a very mild form

The cardiologist will be your final word.