Clarification on a few odds and ends...

[JennKay]

Hi all,

I came across this while searching the internet and had never heard of it before -

"NE also acts on β-1 receptors in the myocardium, resulting in a mild increase in myocardial contractility and myocardial oxygen requirements. However, NE has minimal effect on cardiac output and heart rate as the increase in afterload from α-1 stimulation results in a reflex bradycardia."

NE = norepinephrine 

https://www.openanesthesia.org/norepinephrine_cv_effects/#:~:text=NE also acts on β,results in a reflex bradycardia.

Has anyone ever heard of reflex bradycardia or has anyone ever had a doctor mention it? I will have moments where my HR drops into the low 50s, usually only in the morning after I take the dog for a walk (presumably when my NE and epinephrine would be elevated). I am usually asymptomatic when it happens, but I have always wondered why I would be in bradycardia. I'm no longer doing vigorous exercise like I used to, and I take a beta blocker, but only half of a single dose so I don't think the beta blocker should be having that much of an effect on my pulse. I think this "reflex bradycardia" could potentially be what is going on.

Thoughts from the group? I know I have read older posts where someone will say that all of a sudden they are dealing with bradycardia while flaring or it will happen just out of the blue.

[Pistol]

@JennKay thanks or the article! I have HPOTS as well as NCS. During my first TTT I passed out because I went into tachycardia and suddenly my HR went from high to 50 and I passed out. In my case excessive NE will usually cause a rise in HR and BP due to constricted vessels. But at times the body compensates for this with another faulty ANS response, causing HR and BP to drop from a sudden release of the vessels, causing syncope or presyncope ( which means almost fainting ). 

In the first several years of my illness I had tons of heart monitors and even an implanted monitor. They would show periods of bradycardia following extended periods of tachycardia. Often this would cause dizziness and lightheadedness. Noteworthy to mention is the fact that during episodes of bradycardia my PVC's would also increase. 

[MikeO]

I get some Junctional escapes that result in Bradycardia that at least in the clinical setting have been asymptomatic. These also coincide with transient drops in blood pressure. I also get the other side of the spectrum and will suddenly get a sharp rise in HR. these are almost always symptomatic. 

[JennKay]

Thanks for the thoughts and experiences! I am beginning to wonder if I am in a constant state of reflex bradycardia then b/c my PVCs correlate with a low resting pulse. I think I posted a screen shot of my last heart monitor showing that my PVCs follow a diurnal pattern with more at night.

[JennKay]

One more thought!! I guess this means that for some of us our vagal response is both friend and foe (b/c it is still active, just over active or inappropriately activated) while others don't have the same vagal activity to lower their pulse -- making their phenotype more like traditional POTS with a sustained elevated HR in response to NE. 

[Sushi]

Then there is tachy-brady syndrome otherwise known as sick sinus syndrome. I was diagnosed with that and now have a pacemaker.