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Unusual Patient -- Pulse Pressure Varying Every Few Seconds

  1. Mar 15, 2015 #1

    berkeman

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    As part of an EMT shift at an athletic event yesterday, I took vitals on a 45y/o female Pt who had completed the stressful event about 30 minutes prior. She is very fit and experienced in athletic competition.

    When I was auscultating her BP, I thought that it sounded like she was skipping some heartbeats or had an irregular heart rhythm. I usually take the BP both on the way up and the way down (and estimate HR while I can hear the pulse), and I definitely heard something going on with her heart rhythm. So after the BP I spent a minute or so listening to (well, palpating) her radial pulse, and I felt something that I'd never felt before.

    Vitals: HR 60 (irreg?), RR 12, BP 128/78 (irreg?)

    Her pulse pressure was varying over the course of every 6-10 beats or so. Her systolic pressure for most of the beats was 128, but I could feel that some of the beats occasionally were much softer under my palpation. Strange!

    So I talked with her a bit about it, and her HX showed no cardiac issues. I know that pulse pressure varies over the course of physical exertion and exercise, but up until now I'd only seen smoothly varying pulse pressures that increased with exertion, and returned to normal smoothly over a period of many minutes. See for example this study:

    circ.ahajournals.org/content/18/2/249.full.pdf

    I showed her how to take her radial pulse so that she could see if it happened consistently after exercise (or even without exercise...), and asked her to talk about it with her doctor when she saw him/her next. Does anybody know of pathologies or other causes that can result in a pulse pressure varying over the course of just a few heartbeats?


    EDIT -- While I was palpating her pulse, the rate turned out to be regular, and it was just the varying pulse pressure that made me think it was irregular during the previous auscultation.
     
    Last edited: Mar 16, 2015
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  3. Mar 16, 2015 #2

    Doug Huffman

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    I am an ageing serious cyclist with a cardiac history; athletic heart syndrome, cardio-neurogenic hypotension and EMT training long ago.

    You may be describing Pulsus bigeminus that is a sign of hypertrophic obstructive cardiomyopathy that is a leading cause of sudden death in young athletes. I hope you urged her to a cardiologist or sports medicine physiatrist.
     
  4. Mar 16, 2015 #3

    lisab

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    Did her pulse rate coincide with her breathing?
     
  5. Mar 16, 2015 #4

    berkeman

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    Thanks for the search term, Doug. Interesting syndrome. It doesn't fit exactly, but does have some characteristics that would seem to be related. I did tell her to talk with her doctor about it.

    Good thought. I didn't explicitly think of that (but I probably should have), but the weak pulse beats were pretty random, so I don't think they were related to her respirations.
     
    Last edited: Mar 16, 2015
  6. Mar 25, 2015 #5
    Perhaps it is some sort of heart block. This would be consistent with bradycardia and an irregular rhythm. Was an ECG performed?
     
  7. Mar 25, 2015 #6

    berkeman

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    I would have loved to hook her up to an EKG to see what was going on. Unfortunately this was a BLS standby shift for me, so I only had my EMT equipment with me. I could have hooked her up to my AED (ZOLL AEDPlus) which has a small Lead-II monitor, but that would probably have scared her too much anyway. :smile: Hopefully by now she has talked with her doctor about it, and they have done a 12-lead EKG (and maybe a treadmill stress test)...
     
  8. Mar 28, 2015 #7

    bobze

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    I suspect if she is a "healthy 45yoF" well accustomed to athletic competition this would not be the case. As you mention, the important word is young when we think of pt's with HOCM.
    It’s hard to know without being able to examine the patient myself and without the knowing all the exact details (why doctoring over the internet is bad in the first place, but since this is more seeking info question than diagnosis question, I digress). If I had to make a hypothesis, and you adding more detail to flesh out my story wouldn't hurt, I would suspect you were feeling PVCs. If this is one of those ironman racing/extreme race etc competitions that are going around (and seem to frequent my facebook page by my young "fit-crowd" friends) there’s a good chance after all the exertion and "stressful events" 30 minutes prior depleted her electrolytes. This can cause PVCs or "premature ventricular contractions".

    PVCs can happen for a lot of reasons, in older people or the people I'm sitting and watching on the monitors in the ICU right now its normally because they have had some kind of injury or insult to their heart. Either the myocardium itself or the condution system. In younger individuals or otherwise healthy individuals its most likely 2/t (sorry 2/t=secondary too, in note writing mode) electrolyte disturbances. Even within the normal range of K (potassium) and Mg (magnesium) you can get conduction or arrhythmic abnormalities. Which is typically why in our cards patients we are very strict with the saying "K>4, Mg>2".

    Anyway, PVCs. PVCs are beats that arise in the ventricular myocardium, outside the SA node. The ventricular myocardium actually makes a poor conduction system for delivering a synchronic depolarization and results is a wimpy, "fizzle" beat. If a heartbeat could a cartoon character, think of a PVC as a Milhouse:
    222px-Milhouse.PNG

    You get a weak beat with poor LV output and thus a low systolic pulse for that “cycle” (though remember it’s not really the cycle, it’s a squeezed in beat). But that still is probably not the whole story to you feeling a difference. When patients can feel their PVCs they don’t actually feel the extra squeezed in wimpy beat. What they feel is the beat after.

    After a PVC the myocardium becomes refractory and you get a slight pause. What those wiley cardiologist deem a “compensatory pause”, while the conduction system resets, so to say.
    http://www.learntheheart.com/assets/1/7/PVCExample.jpg [Broken]


    Here’s the neat part in laymen’s terms. While you’re in this prolong pause your myocytes continue on their merry day doing what myocytes do; moving ions. They aren’t smart though (your myocytes) so they “over balance” your ions in the wrong direction. This means on the next beat you get a larger shift in ions which increases the “forcefulness” of the next contraction. The technical term we dub; inotropy. We use certain medications to do this in patients with “weak heart beats”, like digoxin. Positive inotropy generates a larger stroke volume and thus larger systolic pressure.* *

    Essentially what the PVC has done is to give your heart a 1 beat +inotrope. What all this means for your question is, I suspect you were feeling the consequences of the PVCs. Not likely the PVC itself, but the more increased pressure on the following beat, though by finger touch alone on a radial pulse it would be hard to realize that it was the increase in systolic pressure on the next beat and not decreased systolic on the previous beat you were feeling. If we wanted to loose a medical license, we could have sunk an A-line in her arm and while putting her on your 2 lead and watched the slight dip in SBP on the pvc, followed by a bump in the following beat. As its stands though, I’ll keep my license where it belongs in my back pocket :P (okay, okay over in my administrative office)

    **And because this is a predominantly math and physics site what is a post without some math and physics. Recall your blood pressure(BP) is given by cardiac output(CO) x resistance(R).

    CO is the measure of end diastolic volume (EDV) minus end systolic volume (ESV) x your HR.

    The difference in your EDV and ESV, by definition is your stroke volume. Thus;

    BP= (SV*HR)*R
    Thus your Bp is increased with your stroke volume, which we established above is increased on the beat following a PVC.
     
    Last edited by a moderator: May 7, 2017
  9. Mar 29, 2015 #8

    berkeman

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    Thanks for the great reply, bobze. It does sound like PVCs are a good candidate for explaining her condition.

    The event was a Masters swim meet, and she had won her age group in the event that she had swum 30 minutes prior. It might have been the 400yd IM or something similarly difficult.

    I didn't feel an elevated systolic pulse on the beat after the very faint one, but I didn't know to look for that, so I may have missed it. The faint beat was present, just very, very faint. At first I thought they were skipped beats (which are also common after athletic stress), but spending more time and feeling (gently) deeper, I could pick up the faint beats when they happened.

    :smile:
     
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