Left & Right Axis Deviation

Tal

Tal

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Hi all,
we just started the ECG part in my IDF Paramedics course, and I dont understand how come LBBB cause a left axis deviation and RBBB cause right axis deviation?

my logic is that: while there is a block in the RBB we will see the conduct poorer in the RBB and it will seen like the axis is on the left. apparently im wrong, can somone help me understand it?

thanks in advance
 
Try Dale Dubin and also Bob Pages books. They really help you simply and understand what all is being seen and done with the EKG's.
 
thanks...is there any website the actully explain it, all the site I found only write it as a reason without any explaination
 
As it was explained in class last night:

Infarcts cause a bundle branch block, right?
Infarcts can cause axis deviation, right?

If you have a right-sided infarct, you get a right-sided Bundle Branch Block... and the axis deviates LEFT... because that is where the "good tissue" that is still conducting is.

Caveat - I'm a little foggy... last night was our HUGE cardiology lecture - 4+ hours... and it was a LOT of material. - can one of the folks who isn't a student help me out?
 
Jon said:
As it was explained in class last night:

Infarcts cause a bundle branch block, right?
Infarcts can cause axis deviation, right?

If you have a right-sided infarct, you get a right-sided Bundle Branch Block... and the axis deviates LEFT... because that is where the "good tissue" that is still conducting is.

Caveat - I'm a little foggy... last night was our HUGE cardiology lecture - 4+ hours... and it was a LOT of material. - can one of the folks who isn't a student help me out?
Click to expand...

Actually Jon, ill try to expand the general insight here a little bit as well. BBBs also routinely result from cardiac surgery in patients that have had congenital defect repair and sometimes even CABG. Healthy heart tissue is incised and produces characteristic EKG changes associated with BBB. Pulmonary embolus is suspect for RBBB.

New onset BBB can indicate ischemia when there is no surgical history for the heart.

OP, you might poke around here
http://www.EmergencyEKG.com/
and maybe even buy the book.
 
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Tal said:
Hi all,
we just started the ECG part in my IDF Paramedics course, and I dont understand how come LBBB cause a left axis deviation and RBBB cause right axis deviation?

my logic is that: while there is a block in the RBB we will see the conduct poorer in the RBB and it will seen like the axis is on the left. apparently im wrong, can somone help me understand it?

thanks in advance
Click to expand...

Here's why. Look at a picture of the heart, and imagine electrical current going from the base to the apex. Remember. Current flows. Now with that mental picture, add to it a LBBB. LBBB's block current making the current flow slower. The current will deviate towards the left. So the axis will deviate towards the left.
 
MSDeltaFlt said:
Here's why. Look at a picture of the heart, and imagine electrical current going from the base to the apex. Remember. Current flows. Now with that mental picture, add to it a LBBB. LBBB's block current making the current flow slower. The current will deviate towards the left. So the axis will deviate towards the left.
Click to expand...


so you say because the conductivity in the Brunch itself is demage the pulse will pass throgh the myocard cells (interdcalated disk etc...)?
 
Thanks to all posting. I never heard much about axis deviation in class and this is very helpful.
 
I will be referring from Bob Page's text with a mixture from my notes and what little gray & white matter left. Unfortunately most Paramedic or even twelve lead classes do not emphasize axis deviations and the related consequences.

Left Axis Deviation

Cases such as obesity, the movement of the axis slightly towards the left. This physiological left-axis deviation is a normal occurrence and is no cause for alarm. One can read on P-QRS-T Axis box reading the numbers, the center number is the axis (if the leads are placed on properly).


left.jpg



If the axis does deviate more than -40 up to -90 degrees, something is wrong. This pathological can be determined by an upright complex in Lead I and a negative complex in Leads II and III.

All left axis deviation have + complexes in Lead I and a - complex in lead III. So Lead II is helpful in determining if the deviation is pathological or physiological. A + complex means physiological axis deviation where one would see a negative complex in Lead II would be a pathological left axis.

Right Axis Deviation

Where some patients may have a deviated to the right side. This is especially seen in children and should be considered normal. Where if you do see this in adults a right axis deviation would have a negative deflection in Lead I and a + deflection in Lead III. Lead II could be positive, negative or baseline isoelectric. Again, referring to the axis deviation one would see the axis > than -90 to 180 degrees.
right.jpg


Remember, Right Axis Deviation is considered Pathological in the normal adult and may cause or indicate the patient has :

-Posterior Hemiblock
-Right sided ventricular enlargement (hypertrophy)
-Right sided failure, (Cor Pulmonale)
-P.E.
-Dysrhythmias

Again, remember the EKG is just one piece of the painting. A good assessment of course is needed.

If the axis is deviated and pointing the patients right shoulder, the impulse direction is mainly backward and is called by most as extreme right axis deviation . Leads I, II, and III would have a negative complex.

Since this would be originating in the ventricles, the complex would be wide, fast, and truthfully should be considered V-tach.

Hemiblock

Axis deviation indicate hemiblocks. Most define a Hemiblock as one of two fascicles of the Left Bundle Branch (L B B).
Please remember that there is a RBB and a LBB that divides into two separate fascicles, or as Bob refers to as hemifascicles. These are more defined as the left anterior & the left posterior.... and the RBB make up the trifascicular system.

There is much more important information about Hemiblocks. I can post later if interested.

R/r 911

Page, Bob; Pearson Prentice Hall/Brady;2005;Twelve Lead ECG for Acute & Critical Providers
 
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Ridryder911 said:
I will be referring from Bob Page's text with a mixture from my notes and what little gray & white matter left. Unfortunately most Paramedic or even twelve lead classes do not emphasize axis deviations and the related consequences.

Left Axis Deviation

Cases such as obesity, the movement of the axis slightly towards the left. This physiological left-axis deviation is a normal occurrence and is no cause for alarm. One can read on P-QRS-T Axis box reading the numbers, the center number is the axis (if the leads are placed on properly).


left.jpg



If the axis does deviate more than -40 up to -90 degrees, something is wrong. This pathological can be determined by an upright complex in Lead I and a negative complex in Leads II and III.

All left axis deviation have + complexes in Lead I and a - complex in lead III. So Lead II is helpful in determining if the deviation is pathological or physiological. A + complex means physiological axis deviation where one would see a negative complex in Lead II would be a pathological left axis.

Right Axis Deviation

Where some patients may have a deviated to the right side. This is especially seen in children and should be considered normal. Where if you do see this in adults a right axis deviation would have a negative deflection in Lead I and a + deflection in Lead III. Lead II could be positive, negative or baseline isoelectric. Again, referring to the axis deviation one would see the axis > than -90 to 180 degrees.
right.jpg


Remember, Right Axis Deviation is considered Pathological in the normal adult and may cause or indicate the patient has :

-Posterior Hemiblock
-Right sided ventricular enlargement (hypertrophy)
-Right sided failure, (Cor Pulmonale)
-P.E.
-Dysrhythmias

Again, remember the EKG is just one piece of the painting. A good assessment of course is needed.

If the axis is deviated and pointing the patients right shoulder, the impulse direction is mainly backward and is called by most as extreme right axis deviation . Leads I, II, and III would have a negative complex.

Since this would be originating in the ventricles, the complex would be wide, fast, and truthfully should be considered V-tach.

Hemiblock

Axis deviation indicate hemiblocks. Most define a Hemiblock as one of two fascicles of the Left Bundle Branch (L B B).
Please remember that there is a RBB and a LBB that divides into two separate fascicles, or as Bob refers to as hemifascicles. These are more defined as the left anterior & the left posterior.... and the RBB make up the trifascicular system.

There is much more important information about Hemiblocks. I can post later if interested.

R/r 911

Page, Bob; Pearson Prentice Hall/Brady;2005;Twelve Lead ECG for Acute & Critical Providers
Click to expand...

Please do!
 
You can take a tutoral on axis deviation on my PH12ECG blog here.

To answer your questions, with a LBBB (when the left bundle branch is blocked), the right ventricle depolarizes first. So you have late right-to-left ventricular depolarization. Typically the axis is only slightly left with LBBB, so a negative QRS complex in lead III is normal, but lead II is usually upright or equiphasic. A pathological left axis deviation in the presence of LBBB is only significant for higher mortality. Of note, a paced rhythm will show LBBB morphology with a left axis deviation when the pacing lead is in the apex of the right ventricle.

With a RBBB (when the right bundle branch is blocked), the left ventricle depolarizes first, so you have late left-to-right ventricular depolarization (responsible for the terminal R wave in lead V1 and slurred S wave in lead I). The axis will not typically be abnormal. If you have a RBBB with a right axis deviation, then it may be a bifascicular block RBBB/LPFB. If you have RBBB and left axis deviation, it may be a bifascicular block RBBB/LAFB.

This depends somewhat on what school of thought you come from with regard to axis deviation. Most people measure the amplitude (or depth) of the QRS complex without regard to the area of the waves above and below the isoelectric line. Others think the area matters. I personally don't consider the area of the waves, just the amplitude.
 
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