Recent Sinus Ablation

In Jan, 07, I developed episodes of rapid heart rate and inc B/P.  Average would be 154/105-P-122.  Had all kinds of tests, angiogram inc, and dr determied was atrial fibrillation/put me on Rythmol SR 325 MG 2 X's daily.  This did control the heart rythym and BP.  2nd opinion said not atrial fib as my HR was regular even when racing.  Referred me to arrythmia specialist who did a Sinus Ablation.  After or during the procedure, while checking out my heart, it was discovered I had problems with the AV Node and since the ablation, about 10 days ago, I have had almost continuous rapid heart rate, still not irregular, but it does not drop back to normal as before.  It will stay in the 90's to 120's almost all day.  Up until this episode in Jan of this year, I have been relatively healthy, just before this happened, I was diagnosed with high cholesterol.  I am female, 65 years of age and really worried about what is going on.  The dr who did the ablasion said he did not know what caused the AV Node to react this way after the sinus node ablation, but said he would speak with professors and read journals to find a cause.  In the meantime, I'm on no medication and feel ok other than being ansious about my condition.  When I asked the dr what to be aware of all his office staff said was to call if my pulse rate got up around 200.  What should I be looking for as far as life threatening situations? What can be causing this? What is the prognosis?  Thanks for any info you can give me.