Sinus node reentry tachycardia

[gdeniseg]

I am a 31 year old female (weight 138 lb.) who has been having noticable tachycardia for a little over a year now.  I had an echo which was completely normal and I wore a Holter monitor that showed I was having short runs of SVT (about 4 beats), so at that time nothing was done about the SVT - and the Holter also showed my heart rate got down to 49 during sleep, so they elected not to treat me with any medication at that time.  However, in November I suddenly developed a heart rate around 150-160 and ended up in the ER.  My EKG was interpreted as SVT.  However vagal maneuvers failed to stop it, so Adenosine was administered which also failed to stop it.  At that time my cardiologist was contacted and she suggested putting me on Cardizem drip which did bring my rate down to around 110.  When my cardiologist saw me the next day she stated that she saw small p-waves and that she thought I had 'sinus node reentry tachycardia'.  So I was also started on Lopressor 50 mg. bid which keeps my heart rate about 50 to 60 most of the time, which I love because I mentally can't tolerate tachycardia.  
My questions are:  I have tried to research SNRT but cannot find any relevent info about it.  What is it?  What causes it?  How is it different from SVT?  Does it mean I have any kind of heart disease?  Do you think the Lopressor is causing my heart rate to go lower than 49 during sleep?
I also work in the medical field and very much appreciate your valuable time.   Thanks so much.

[CCF-M.D.-MJM]

Hi gdeniseg,

SNRT is not an introductory level arrhythmia.....

Reentry is a common mechanism for arrhythmia.  It refers to an "electrical" circuit that forms and "over powers" the normal conduction chain of sinus node -- AV node -- ventricle.  The circuit fires at a much faster rate than normal sinus rhythm and essentially suppresses it by pacing at a much faster rate.

As far as what causes, I am afraid I can't fully answer that question without a chalk board and a lot of time--if you don't have a medical background.  It requires two separate pathways.  A fast pathway that recovers slowly and a slow pathway the recovers quickly.  I perfectly timed premature beat induces block in one of the pathways, usually the slow pathway.  With the next regularly timed beat, the slow pathway is now recovered.  The block in the fast pathway recovers by the time it meets the slow pathway allowing conduction up the opposite direction.  This forms a reentry circuit.  If the reentry circuit does not involve the AV node, it is unlikely that adenosine will break the SNRT.

How is it different from SVT?
SVT describes any arrhythmia that originates above the ventricle, hence supraventricular tachycardia (SVT).  It is not a type of arrhythmia, rather a category under which many of other arrhythmias apply including: AVNRT, AVRT, atrial fib., a. flutter, a. tach, etc.


Do you think the Lopressor is causing my heart rate to go lower than 49 during sleep?
Sure it could, but I wouldn't think twice about a rate of 49 -- it’s normal for the heart to slow down during sleep.


I hope this helps.

[tickertock]

snrt , very interesting sinoatrial nodal reentrant tachycardia, usually slower than most svts 120-150 bpm, imitates sinus tachycardia, usually ivolves a reentrant loop very close or near the sinus or sinoatrial node. do a google search on sinoatrial nodal reentrant tachycardia, sinus node rentry tachycardia is the same thing.

[Neener44]

I'm not sure if my heart will go back to normal size and it's been over 4 years since my last echo. I see my ep doctor again next month maybe I'll ask him. From what I've read it is possible for your heart to go back to normal if it's not too enlarged. I don't have as many symptoms as I use to so I think I'm doing better overall. At first meds did not work for me and now after two procedures my heart rate is pretty well controlled with sotalol. I can get my rate up pretty high with exercise though and I'm also very sensitive to heat. Hope the lopressor keeps working for you. I know the ep study and ablation sounds really scary, but it really is not that bad. You just need to make sure you have an excellent doctor with tons of experience. My doctor does at least two procedures each weekday morning 4 to 5 days per week. Take care.
Neener