ECG Question

[VickyRN]

Is it true that ST elevation/ depression and T wave changes from certain electrolyte imbalances (tented, flat) can only reliably be confirmed on a 12-lead ECG (as opposed to 5-lead bedside monitoring)? Thanks in advance :)

[papawjohn]

Hey Jubei

This is an interesting topic. Could ya cite the books?

thanx

Papaw John

[DeputyParamedicFF]

Yes, the 12 lead monitors have higher diagnostic qualities, see link and rationale below. Hope this helps...

http://www.medtronic-ers.com/documents/12Lead.pdf

FREQUENCY RESPONSE

12-lead ECG recordings should always be performed in diagnostic

frequency response. Diagnostic frequency response records ECG signals in

a wide range (.05 to 150Hz) resulting in signal characteristics that would be

filtered out in the narrower bandwidth of the common monitor frequency

response (typically 1 to 30Hz or 0.5 to 40Hz).

To understand concept of frequencies and their relation to the ECG,

consider music. High pitched, or treble sounds are actually high frequency

sound waves. Low pitched, or bass sounds are sound waves that occur at

low frequencies. When you adjust the treble or bass control on the stereo

receiver you cause it to filter out certain frequencies along the spectrum of

sound waves to suit your personal taste. The result is that some sound

frequencies are authentically reproduced by the speakers, while others

are damped or removed.

11

1 / EQUIPMENT AND SKILLS

When the heart generates and conducts an impulse it produces an

electrical signal much like the music in that it contains a broad spectrum of

frequencies. The bandwidth or frequency response of an ECG monitor, like

the stereo receiver, defines the range of frequencies that can be authentically

reproduced on the display or the ECG recording. But unlike the stereo

receiver the monitor offers a limited selection of bandwidths. In electrocardiography,

the broad bandwidth is referred to as "diagnostic frequency

response" or DIAG; the range of frequencies reliably reproduced is 0.05

(low end) to 100 or 150Hz (high end). Diagnostic frequency response is

particularly important when trying to diagnose myocardial ischemia or

injury by observing for abnormalities in the ST segment and/or T wave;

these are low frequency signals.

* Use diagnostic frequency response (DIAG) for 12-lead ECGs

* DIAG bandwidth is 0.05 to 150Hz

* DIAG authentically reproduces ST segment on the ECG

A more narrow bandwidth called monitor frequency response (MON)

will accurately reproduce frequencies between 0.5 to 40Hz or 1.0 to 30Hz

depending on the device and the selections available. Monitor frequency

response is very useful for routine ECG recording (rhythm strips) because

it filters out much of the "noise" from muscle artifact (high frequency

signals). The more narrow bandwidth also stabilizes the baseline which

would otherwise "wander" when the device is subjected to a motion

environment (a source of low frequency signals).

* Use monitor frequency response (MON) for rate and

rhythm determinations

* MON bandwidth is 0.5 to 40Hz or 1 to 30Hz

* MON distorts ST segment on the ECG

Many monitor recorders have both monitor and diagnostic frequency

response options available to the operator who can select the frequency

response in which to record the cardiac signal. The monitor screen of these

devices, however, is limited to monitor frequency response because of

limitations in display technology, and the desire for less visible noise

appearing on the screen.

Monitor frequency response is not suitable for determinations about

ST segment elevation or depression because it does not reproduce the ST

segment accurately on the recording or on the screen. In some cases it may

show ST elevation or depression where none exists and in others diminish

the degree or entirely cancel out the baseline deviation.

[chadash]

ST depression yes, but I was asking about elevation...

I think, I dont know, but doesnt hyperkalemia cause tenting T, but not ST segment elevation. Think the st segment is still at baseline..

[chadash]

Whoops! didnt read the second pages of post before I posted! Let this be a lesson to me;)

[chadash]

do have a question about heart blocks: any great ideas to help readily differentiate one from another?

[papawjohn]

Hey Chadash

There's lots of places you can look up the business of 1st degree, 2d degree, mobitz 1 and mobitz 2, etc. There are some of us compulsive enough to think about facsicular blocks and such. Have you looked around the web or into your books? Do you have a specific question? There's several of us out here that like to teach but the question is awfully broad.

Papaw John

[chadash]

The question is sooo broad, cause I dont know enough to know what to ask.

I just know, when I try to recognize the differences, I mess up.

[mitchsmom]

pp. 222-224 of ECG's Made Easy 2nd ed. by Aehlert is titled "ECG changes associated with electrolyte disturbances" and mentions the flattened/peaked T wave & widened QRS with hypo/hyperkalemia among other things. There is a chart with hypo/hyper -calcemia, -kalemia, & -magnesemia with the changes to each part of the ECG.

It even has 6 tracings of a patient going from K+ 1.9 at 11am to K+ 8.1 at 10:45pm to illustrate.

I think, I dont know, but doesnt hyperkalemia cause tenting T, but not ST segment elevation. Think the st segment is still at baseline..

...same book says for ST segment & hypoK+ = "depressed", for hyperK+ = "disappears as level increases". For T wave, it says"flattened; U wave present" for hypoK+ and "tall, peaked/tented" for hyperK+. I guess that's basically what you said, just didn't know if you'd like the info. :)

Here's a page about blocks, chadash:

http://www.randylarson.com/acls/blocks.html

Here's the beginning page with all kinds of ACLS/ECG stuff - great for learning rhythms!:

http://www.randylarson.com/acls/

[chadash]

:cheers: Thank ye!

[chadash]

Some many questions! so little time...

If you have Monomorphic VT, with a pulse, can you do sychronized cardioversion? but poly morphic, unsychronized?

somebody help me!!!!!!!

[challenged annie]

Sorry bit slow but to the heart block question

1st degree= distance between p and QRS complex but one to one

2nd degree= two p waves to each qrs

3rd degree= no coordination between p and QRS complexes

[challenged annie]

oh yeah and to the electrolyte question magnesium plays important part too