Beta Blockers and sinus tachycardia

[Claudia]

My heart rate is constantly elevated (around 100 bpm) and goes much higher when under stress or exercise.  Under stress it's been as high as 175 bpm.
After going to 3 cardiologists, the last of them an Electrophysiogist from John Hopkins med. center at Baltimore, and after EKG's, an echo, and holter monitor, I was diagnosed with Sinus tachycardia.
I was put on Toprol-xl 50 mg, and at first my heart rate went down to the low 80's, but my blood pressure went down as well to as low as 85/65 (used to be around 100/70).  After a couple of months and some stressful days, the toprol is not as effective, and my pulse is in the 90's at rest and my blood pressure about normal.  
I'm going for surgery next week (major surgery not related to heart); I was supposed to have this surgery months ago, but cancelled when ready in pre-op due to high pulse (went to 160 bpm because of anxiety of surgery, even with Toprol).  I normally suffer from anxiety and panic attacks.
My questions are:
1) My doctor says that nothing is wrong with my heart so I don't need to increase the Toprol, but since I get so anxious with this surgery, I can double the dose the day of the surgery, that this sound reasonable to you?

2)  My blood pressure went low when started Toprol, will double the dose that day bring my BP too low?  Will the anxiety avoid my BP from going too low? (it gets higher with anxiety as well)?  Isn't it dangerous to increase the dose when having gral anesthesia?

3)  I have not had an EP study, is it possible to tell by EKG's, holter and echo I have sinus tachycardia? (my pulse is constantly high).  All cardiolgists said I have sinus tachycardia.

4)  How come Toprol was effective at first and then decreased it effectiveness?

Thank you so much for your help,

Claudia

[Leah]

Ever hear of rapid heart beat(200 plus , blooodshot eyes and pounding head---------all occuring just before having a loose bowel movement? It then stops abruptly after the bowel movement.
Thanks, Leah

[JR]

that probably 120bpm every once in awhile wouldnt be that bad!...some poor people (me included) go up to 250bpm and fall down in the floor turning blue....be glad you only have an overactive adrenal gland!

[LS]

I haven't been diagnosed w/ sinus tachycardia but I have episode of rapid heart beat around 120 for no reason...even when I don't feel stressed.  My resting heart rate is normally about 90 but sometimes lower and sometimes just over 100.  I do have mitral valve prolapse and was taking a beta blocker, but not anymore.  Anyway, before I knew of my MVP, I had an iridologist look into my eyes and she said that I had an overactive adrenal gland.  I asked what that meant and she just said that it wasn't good. I felt fine and just dismissed it.  Now, however, I wonder if that is the cause of my episodes of rapid heart beat more so than just a symptom of MVP.  Just a thought....

[Cleveland Clinic, MD]

Dear Claudia,
It sounds as if you have been diagnosed with inappropriate sinus tachycardia.  There are other postings on this site that deal with that topic that you can also read.  I have tried as best as possible to answer your specific questions.  As to questions about medication doses only your doctor can answer those for your situation.

1) My doctor says that nothing is wrong with my heart so I don't need to increase the Toprol, but since I get so
     anxious with this surgery, I can double the dose the day of the surgery, that this sound reasonable to you?
A: This is probably OK but you will need to check with your doctor for what is best for you.

     2) My blood pressure went low when started Toprol, will double the dose that day bring my BP too low? Will the
        anxiety avoid my BP from going too low? (it gets higher with anxiety as well)? Isn't it dangerous to increase the
     dose when having gral anesthesia?
A: Yes, it is possible  that doubling the dosage could bring your blood pressure too low.  Again, your doctor will have to coordinate with anesthesia the best way to handle your tachycardia during surgery.

     3) I have not had an EP study, is it possible to tell by EKG's, holter and echo I have sinus tachycardia? (my pulse
     is constantly high). All cardiolgists said I have sinus tachycardia.
A: If they have been able to 'capture' the tachycardia on some recording (e.g Holter monitor) they can be reasonably certain that it is inappropriate sinus tachycardia.  

     4) How come Toprol was effective at first and then decreased it effectiveness?
A: This is due to what is called 'tachyphalaxis' which means the body becomes adapted to a certain dosage and usually indicates a need to increase the medication slightly.  50 mg of Toprol is not a big dose so your doctor has room to increase the dosage.