Malignant Vasovagal Syncope

What is the role of the vagus nerve in malignant vasovagal syncope?  
What is the meaning of "hypertone" in a nerve?  
Why does my hypertone stop my heart and drop my BP to where it can't be detected?  
I have had CPR  and after many tests, it eventually lead to measured asystoles of 38, 17 and 31 seconds on three differing tilt tests.  Even with injected Atropine I lost all BP on retilt and passed out.  This demonstrated that a pacemaker wouldn't keep me going.

What is the role of insulin hypersensitivity in syncope?  Would metformin help or hurt in this situation?  Thanks.

[AireScottie]

I've never heard "malignant" used with vasovagal syncope.  Is this different from regular vasovagal syncope?  I too have been asystole with tilt tests, but haven't ever been told it's malignant.

Finding a cause for this can be a very long process.  I was told my vagus nerve was the problem for some time, but in the end, it turned out the problem was peripheral neuropathy (from an autoimmune disease) and nothing to do with the vagus nerve.  If you're looking for a cause, basic tilt tests are probably not enough.  What other tests have you had?  Catecholamine levels?  Hemodynamics?  24 hour Holter monitor?  When you ask about insulin sensitivity, do you mean actual diabetes or not?  Because diabetes is a MAJOR cause of peripheral neuropathy, which can kill off your autonomic nerves and make BP and heart rate regulation almost impossible.

[supineallthetime]

I'd guess that hypertone is a ways of saying the nerve or something signaling it is hypersensitive to an otherwise normal stimulation (like the signal is amplified).  I've heard that sort of thing in regard to the "baroreflex" which is the response to variation in blood pressure that is supposed to keep things balanced, especially during "orthostatic" stress (flow changes from standing up).

The vagus is like a "backbone" to the nervous system through the body, the autonomic nervous system.  It comes down and branches out to various areas for both sensing and control.  Signals down the vagus can do things like heart rate & volume changes, sweating, etc.  It's not the entire picture, since things in the blood can induce changes too... but it's the key nervous system control.

There are two generally opposing divisions, the sympathetic and the parasympathetic.  I think as far as the heart goes sympathetic stimulation tends to speed things up and parasympathetic tends to slow things down.  So in your case they might be referring to a "hypertone" of the parasympathetic aspect of the vagus... which would cause a drastic dive in heart rate, volume, etc. and BP.  It can also be bad sensors somewhere... or "hypertone" in the sensor signal perhaps... causing an otherwise functioning autonomic nervous system to respond badly.  Or the "central" processing of these signals can be goofed or skewed for some reason.  There could also be "denervation" which takes away half of the balancing act... leaving a bad instability... but that wouldn't be called "hypertone".

[Heiferly]

There's way too much here for me to address at once.  I'm going to start at the beginning, since the term "malignant vasovagal syncope" is new to our forum, and begin with a brief discussion of that.  I apologize for however long it's going to take me to fully address these questions.  (SandOne, you may not be aware but I'm just now recovering from a setback in my own health and am plodding along as best I can, so everyone has been kindly bearing with me.  Thanks in advance for your patience.)

"The use of the term 'malignant vasovagal syncope' also merits comment. The original description emphasised [sic] a prolonged asystolic response during head up tilt.4 The term has now been broadened to denote clinical characteristics (frequent syncope without warning and/or traumatic outcome). As a following article in the same issue reports,5 the term malignant may be more emotive than scientifically accurate and consensus on its appropriateness is overdue."

from Warren Smith, Green Lane Hospital, Auckland, New Zealand's Letter to the Editor.   Heart 1998;79:105; doi:10.1136/hrt.79.1.105
Copyright © 1998 BMJ Publishing Group Ltd & British Cardiovascular Society

http://heart.bmj.com/cgi/content/full/79/1/105  accessed 1 Oct 2009

(The author's response is interesting as well for anyone with the time/inclination to check this one out ... use the URL I included above.  You may need to register--at no cost--to view it.)

"Hypertone" is, essentially, a state of being excessively responsive to stimuli.  

(To be continued...)