St Elevation

VFlutter

VFlutter

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Hey guys,

I am currently an Emt-B working as a monitor tech at a hospital. I am fairly new so sorry if this is a dumb question. What is the normal amplitude of a St segment? I had a pt with what I thought looked like St elevation however the nurse did not really seem worried. The amp in the leads was II 2.8, aVR -2.1, I 1.3, III 1.4, and aVL -.01. I will try to post a strip later. Pt was sinus tach 120s with frequent PVCs. But is it dependent on the pt and past history or what is considered substantial St elevation? Thank you
 
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ChaseZ33 said:
Hey guys,

I am currently an Emt-B working as a monitor tech at a hospital. I am fairly new so sorry if this is a dumb question. What is the normal amplitude of a St segment? I had a pt with what I thought looked like St elevation however the nurse did not really seem worried. The amp in the leads was II 2.8, aVR -2.1, I 1.3, III 1.4, and aVL -.01. I will try to post a strip later. Pt was sinus tach 120s with frequent PVCs. But is it dependent on the pt and past history or what is considered substantial St elevation? Thank you
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More important question. Are you looking at your monitor when trying to determine ST Elevation or are you looking at a 12 lead printout?
 
JPINFV said:
More important question. Are you looking at your monitor when trying to determine ST Elevation or are you looking at a 12 lead printout?
Click to expand...

Both, the 12 lead print out and strip of leads II/III show elevation
 
ChaseZ33 said:
Hey guys,

I am currently an Emt-B working as a monitor tech at a hospital. I am fairly new so sorry if this is a dumb question. What is the normal amplitude of a St segment? I had a pt with what I thought looked like St elevation however the nurse did not really seem worried. The amp in the leads was II 2.8, aVR -2.1, I 1.3, III 1.4, and aVL -.01. I will try to post a strip later. But is it dependent on the pt and past history or what is considered substantial St elevation? Thank you
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It would be helpful to see the ECG to give you a decent answer.

Usually ST elevation > 1mm in the limb / augmented leads, and >2mm in the precordial leads (V1-V6), is considered diagnostic for MI, provided there's changes in two or more anatomically contiguous leads -- i.e. leads looking at the same region of the heart. So in this case, elevation in II and III would meet this criteria.

However, your monitor needs to be recording the ECG using a "diagnostic mode" filter setting to properly measure the ST segment deviation. Typically they default to a "monitor mode" frequency, that can cause false ST elevation or depression. So you really need to know whether the tracing you saw was using filter settings that were going to accurately record the ST segments.

Other conditions can cause changes in the ST segment elevation / depression, e.g. left ventricular hypertrophy, left bundle branch block, benign early repolarisation, pericarditis, etc. There are criteria for analysing ST changes suggestive of MI in the presence of LBBB, but it's probably not worth going into them right now.

It's interesting that you have ST elevation in II and III which view the inferior wall of the left ventricle, and in lead I, which views the lateral wall. Typically these areas are perfused by different coronary arteries. It's interesting to note that the elevation in II is less than III. Typically when the right coronary is blocked, lead III shows greater elevation than lead II. These findings could be seen in someone who has a left coronary circulation that supplies both the inferior and lateral walls of the heart.

So to answer your questions:

- a the normal amplitude is 0 mV / 0 mm in all leads. The ST should be isoelectric with the TP segment (and in most cases the PR segment).

- whether ST elevation is clinically significant depends on both the history / physical exam and the ECG. In some conditions the presence of ST deviation is expected, and may not be due to acute infarction.
 
Here are some pictures from my phone. Sorry they are not the best.

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Thanks for posting those!

Does it have anything on the bottom of the tracing showing the frequency response? It should be in Hertz units, e.g. 0.5-30 Hz, 0.05-150 Hz.

It would also be really helpful to see V2 through V6, to make an educated guess about the presence or absence of left ventricular hypertrophy.

Right now, I see sinus tachycardia (some RR variability suggesting a sinus arrhythmia, probably a normal variant), and some left axis deviation. In these leads the QRS looks narrow, which argues against LBBB, but I can't be sure without a 12-lead. If there's no hypertrophy, there could be a left anterior hemiblock causing the axis deviation.
 
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I will try to get a copy of the real 12 lead. This was from a telemetry monitor so its a little different. Well now the PA is checking it out. Monitor is currently reading 3.6 in lead II and -2.4 in aVR
 
Cool, interesting. Any information about the patient's history and clinical condition? (No identifiers, of course!)

If you're interested in learning more about 12-lead, I found this book was a good start. I think it's currently on the 3rd edition. I used to have the first edition, and I think if you could find it cheap, the information in there is still good.

http://www.amazon.com/12-Lead-ECG-Acute-Coronary-Syndromes/dp/0323077854/ref=dp_ob_title_bk
 
I have limited info about the pt. It's a 81 year old female admitted for CHF, has been SR 80s for most of the day with bursts into the 120s with frequent coughing spells.
 
Things to consider:


Monitors are NOT DIAGNOSTIC. a 5 lead system can give you an IDEA, but they are really only good for rate and rhythm.



Lead placement can affect ST segments.


The first strip you posted looks like jpoint elevation to me. Some people say you must look 0.04 past the jpoint to measure elevation. Some people say up to 0.08.


Also --- a true STEMI will have reciprocal changes and other clues, such as hyperacute t waves and possibly q waves evolving.


Don't forget that there are multiple leads looking at the various surfaces of the heart. You must have these developments in contiguous leads to get anyone excited.


If your nurse isn't listening to you, contact the charge nurse and see if your findings have any effect on them.


Above all... the patient must be assessed. Electricity does weird things considering all of the variables.


example: Chest physiotherapy makes a monitor go wild, I can easily look like Vfib!
 
I'd also like to know the bandwidth. If low frequency / high pass filter is set to 0.05 Hz then my guess it pericarditis but it could be a STEMI. I'd like to see the entire 12-lead ECG but I'm also in agreement that clinical correlation is important.
 
Let's also remember that lead placement is key here. LA means left arm, not left upper chest and so on and so forth.
 
Ive had many patient's on the monitor that appeared to have ST elevation..run the 12-lead and there is no elevation evident at all. Just a difference in monitoring versus diagnostic mode.
 
MSDeltaFlt said:
Let's also remember that lead placement is key here. LA means left arm, not left upper chest and so on and so forth.
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This makes sense, even if it is a slight change in vector, it is still a change in vector...why is it that people are taught that you can place it peripheral or central? Is it monitor dependent? I know 12 lead's have a particular placement specified but what about 3/4/5 leads?
 
NVRob said:
This makes sense, even if it is a slight change in vector, it is still a change in vector...why is it that people are taught that you can place it peripheral or central? Is it monitor dependent? I know 12 lead's have a particular placement specified but what about 3/4/5 leads?
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1. Because it's relatively irrelevant when it comes to monitoring the patient.

2. Try this experiment next time you're in the station. Take an extra 3 lead cable and hook them up to your arms and legs. Now try to walk around, eat, etc. Hence the major reason why they get set up with a central location in the hospital where the patient gets to wear them for an extended period of time.
 
I understand the fact of practicality and artifact. So in standard monitoring (3/4/5 lead) does the lead placement not need to be as precise? I have seen them on wrists, ankles, hips, shoulders, lower abdomin and upper chest including any of the combination of the above, whatever is the easiest accessible location. It would make sense being as you are only trying to get a general picture and not doing a diagnostic test, but would it still not have changes on the reading?
 
NVRob said:
, but would it still not have changes on the reading?
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The question isn't "does it change the reading," but "does it change the reading in any meaningful way?" To the best of my knowledge, especially in light of the different filter setting for monitor vs diagnostic, no. Sinus rhythm isn't going to all of a sudden present as a-fib because the leads moved to a central location.
 
NVRob said:
I understand the fact of practicality and artifact. So in standard monitoring (3/4/5 lead) does the lead placement not need to be as precise? I have seen them on wrists, ankles, hips, shoulders, lower abdomin and upper chest including any of the combination of the above, whatever is the easiest accessible location. It would make sense being as you are only trying to get a general picture and not doing a diagnostic test, but would it still not have changes on the reading?
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If you want to determine axis (which just requires the limb leads), then they should be eqidistant from the center of the chest. Otherwise you're going to bias the axis towards the closest leads, e.g. if you put electrodes on the left and right upper chest, and the left and right ankles, your axis is going to look more superior.

If you're just interested in asking is this NSR or not, then you can put them pretty much anywhere. You may have to look at more than one lead to get a complex that's easy to interpret, but if it's sinus rhythm in one lead, its sinus rhythm in all leads.

If you do a lead II placing electrodes on the right upper chest, and left lower abdomen, the complex is going to look larger, compared to placing them on the right wrist and left ankle.

[This actually partly explains why V5, V6 are slightly less sensitive for infarction compared to the other precordial leads. They're further away from the heart, with a mass of lung and air causing the signal to diminish. ]
 
systemet said:
If you're just interested in asking is this NSR or not, then you can put them pretty much anywhere.
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I think you answered my question.

I'm not saying place them randomly. If they are placed, it should be bilaterally (ie. L/R wrist and L/R ankle) I may be using the wrong term. if so, please excuse me, and correct me :)

I guess my question was; does 3/4/5 lead placement make a huge difference where they are placed, considering they are placed in similar places on the left/right locations of the patient. From what I am reading, and correct me if I'm wrong, that it really doesn't matter.

Is it specific to the monitor that is being used?
 
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