[poohbear1968]

Can someone tell me how I can determine if the ECG is originating in the atria, AV node, and ventricles? I am basically teaching myself. I think If it comes from the sinus node the p wave will be present and upright. I think....

Poohbear

[BBFRN]

I'm having a hard time understanding what you're asking. Do you mind clarifying?

[frodo6657]

An easy way to figure it out, if the QRS complex is wide and looks funny, it's ventricular in nature. Also if the QRS is narrow, it's atrial. If the P wave is .20 seconds or less (5 little boxes) on an ECG, it's from the SA node. If it is longer than those 5 little boxes, it's from the AV node. Hope that helps.

[poohbear1968]

So like in PVC's there may be some narrow QRS complex and then all of a sudden there may be a wide QRS. The wide QRS is ventricular in origin. I think Im getting It!

[EricEnfermero]

You're definitely on the right track. Often the heart rate gives you an idea of the origin as well.

[putmetosleep]

You may want to invest in an EKG interpretation book (you can find them anywhere, Amazon.com has them for reasonable prices) if you're learning on your own. It'll give you some background information about different peices of the EKG (p-waves, QRS, etc) as well as information on different rhythms, how to identify them, what causes them ,etc. They also have many practice rhythm strips for you to interpret. I found it very helpful when I started in ICU as a new grad (with very limited tele experience!).
Good luck to you! I think it's great that you're seeking information independently.

[RNREMT-P]

ekgs can be pretty tough because there's 1000+ different variations. whenever you look at one, look at the rate then the rhythm. then look at the relationship between the p waves and qrs (this will determine any degree of AV block), then the morphology of each complex. then identify any ectopics present.
p waves upright are generally from the atria but can originate near the AV junction, the delay between the complexes of >0.20 sec only indicates a conduction delay through the av node (remember the vagus innervates this). wide bizzare complexes usually originate in the ventricles, but BBBs can appear as idioventricular rhythms.
hope this helps a little. like someone suggested, there are plenty of websites or cardiac workbooks that can help a whole lot. One I used was ECG Self-Diagnosis. I don't know if it's still in print but you could Google it.

[SEOBowhntr]

Originally Posted by frodo6657

An easy way to figure it out, if the QRS complex is wide and looks funny, it's ventricular in nature. Also if the QRS is narrow, it's atrial. If the P wave is .20 seconds or less (5 little boxes) on an ECG, it's from the SA node. If it is longer than those 5 little boxes, it's from the AV node. Hope that helps.

Frodo,
You need to do a little reading. If P-waves are same, even if the PR is .26, for example, it's still coming from the SA node, but the conduction through the AV node is delayed.


To determine the origin of the QRS, you must have an idea what the patients "normal" QRS looks like. I've had many patients that were callled to be in VT, that was only a ST, but they had QRS complexes that were .14-.16 wide as a baseline d/t their cardiomyopathies.

Poohbear,
You are correct for the most part, the P-wave should be present and upright when stimulated from the SA node NORMALLY. I say, "for the most part," because if you have a patient with Left Atrial Enlargement, sometimes you'll have a "biphasic" P-wave the may have the appearance of an M or may start upwards then drop below the "isoelectric line," return the the isoelectric line, and then the QRS follows, and can be wrongly interpretted as junctional, when it is not.

Here's a pic of what I mean:

[richard1980]

A great book for starting out with EKG's is Dale Dubins Rapid Interpretation of EKGS. Easy reading, starts from the begining and leads to more complex rhythms.

[Ventjock]

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