How high can sinus tachycardia be?

I am a 33year old female. For the past 5 years I have had episodes of waking up in the middle of the night with sweating, fear of dying and then my heart rate escalates with tingling in legs and arms. I have had holter, echo, ekg, lab work, and event monitor done. The event monitor showed sinus tach at rates of 150-160 bpm.  One episode which was the worst showed 180 bpm. I almost went to the ER. My cardiologist said the 180 episode was sinus tach. He had an EP specialist look at the strip and concurred. My questions are as follows: 1. Can sinus tach go as high as 180 bpm at rest. 2. Can panic attacks make the heart rate go up that high? 3. Since the last 180 bpm episode I have been on Atenolol 25mg Q day. I have not had my heart race since taking it, although I still wake up in the night with some of the other symptoms. Will I become tolerant to the Atenolol and need to increase the dosage? 4. How can you tell the difference between SVT and sinus tach with that high of a rate and not able to distinguish P waves? I trust my cardiologist, but I have heard from other medical people that sinus tach does not go that high at rest. I do not smoke, drink alcohol or use caffiene.
Thank you.

[CCF-M.D.-CRC]

Dear jocie,
Sinus tachycardia is by definition any heart rate coming from the sinus node between 100 bpm and maximum heart rate.  In your case maximum heart rate is about 190.  If the tachycardia is sinus and is coming at a time when it should not be elevated the term "inappropriate sinus tachycardia" is used.  Panic attacks can and do elevate heart rate.  Atenolol is a good first line drug for inappropriate sinus tachycardia and is generally well tolerated.  Generally once the appropriate dose is given it does not need to be increased.  It would be difficult to distinguish sinus tach from other SVTs without being able to see P waves but may be possible using other clues such as rate, morphology and onset/offset of the tachycardia.

[jmpnjkflsh]

I have had sinus tachacardia at rest of 214bpm as measured by the aicd I have implanted.

The aicd discharged twice within 30 seconds.

It has since been adjusted to tolerate this level unless it persists for longer than 5 minutes.

[Buzz]

What is a aicd implant.   I am very brother by sinus tachycarda.
I;m now on metoprolol 50mg twice a day.