Difference between revisions of "QRS axis"

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m (Examples of a right heartaxis)
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This indicates a normal heartaxis. Usually, these two leads are enough to diagnose a normal heartaxis!
 
This indicates a normal heartaxis. Usually, these two leads are enough to diagnose a normal heartaxis!
  
The biggest vector in the heart is from the AV-node in the direction of the ventricular depolarization. Under normal circulstances, this is directed left and down.(towards leads I and AVF). The position of the QRS vector is given in degrees. See the figure, the middle of the figure is the AV-node. A horizontal ine towards the left arm id defiuned as 0 degrees.
+
The biggest vector in the heart is from the AV-node in the direction of the ventricular depolarization. Under normal circumstances, this is directed left and down.(towards leads I and AVF). The position of the QRS vector is given in degrees. See the figure, the middle of the figure is the AV-node. A horizontal line towards the left arm is defined as 0 degrees.
  
 
A normal heartaxis is between -30 and +90 degrees.
 
A normal heartaxis is between -30 and +90 degrees.
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====Interpretation====
 
====Interpretation====
De interpretatie van de elektrische hartas kent een aantal makkelijk te onthouden regeltjes:
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The interpretation of the electrical heartaxis has a few rules of thumb:
  
* Ten eerste, beweegt een positieve depolarisatiegolf naar een positieve elektrode, dan wordt er een positieve, naar boven gerichte uitslag op het ECG geregistreerd.
+
* First, when a positive depolarization wave moves towards a positive electrode, a positive, upwards deflection is registered on the ECG.
*Ten tweede zijn er 4 gebieden waar de QRS-vector naar kan wijzen:
+
*Second, there are 4 quadrants where the QRS-vector can point to:
**linksboven --> linker asdraaing (tussen -30º en -90º)
+
**left upper quadrant --> left axis deviation (between -30º and -90º)
**linksonder --> normaal gebied (tussen -30º en 90º)
+
**left lower quadrant --> normal (between -30º and 90º)
**rechtsonder en rechts--> rechter asdraaing (tussen 90º en -150º)
+
**right below and right --> right axis deviation (between 90º and -150º)
**rechtsboven --> extreme as (tussen -90º en -150º, dit is zeldzaam)
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**right upper quadrant --> extreme axis (between -90º and -150º)
  
''Bijvoorbeeld'':  
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''Example'':  
  
Het QRS in afleiding I zal bij een rechter asdraaing naar rechtsonder een negatieve uitslag registreren. De vector wijst namelijk niet in de richting van van de electrode. Bekijk je het QRS echter in de AVF afleiding dan zal deze positief zijn. Hier wijst de vector wel in de richting van de electrode.
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The QRS in lead I, will have a negative deflection in a right axis deviation. The vector is not directed towards the electrode. However, lead AVF will be positive, the vector is directed towards the electrode.
  
 
====Heart-axis Simulator====
 
====Heart-axis Simulator====
  
Om goed te begrijpen hoe het ECG verandert bij een asdraai kun je de hart-as simulator gebruiken: http://www.blaufuss.org/ECGviewer/indexFrame2.html
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To understand how the ECG changes in axis deviations, this excellent axis-simulator may be helpful: http://www.blaufuss.org/ECGviewer/indexFrame2.html
  
 
====Iso-electrical====
 
====Iso-electrical====
'''NB:''' Verloopt de depolarisatie loodrecht op de stand van de afleiding dan noemt men dit
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'''Note:''' When the depolarization is perpendicular on the lead, this is called
'''iso-electrisch'''. Dit kan handig zijn om de as nauwkeurig te bepalen. Is afleiding AVF bijvoorbeeld iso-electrisch en I positief, dan is er sprake van een horizontale hartas.
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'''iso-electrical'''. The QRS is neither positive nor negative.  
 +
 
 
====Undetermined axis ====
 
====Undetermined axis ====
Ook kan het zijn dat alle extremiteitsafleidingen min of meer bifasisch zijn. De hartas staat dan vaak naar voren of achteren en de hartas is dan '''niet te bepalen'''.
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When all extremity leads are biphasic, the axis is directed to the front or back, in a transverse plane. The axis is than '''undetermined'''.
 
 
==Anbormal heartaxis==
 
[[Image:left_axis_dev.jpg|thumb| Hartasdraai naar links bij een onderwandinfarct. Linker anterior hemi-blok is ook een veel voorkomende oorzaak. Een linker hartas ligt tussen de -30 en -90 graden. Hier is de hartas ongeveer -30 graden.]]
 
[[Image:right_axis_dev.jpg|thumb| Hartasdraai naar rechts bij rechtsbelasting, zoals bij longembolie en COPD. Een rechter hartas ligt tussen de +90 en +180 graden. Hier is de hartas ongeveer +135 graden]]
 
De richting van de vector kan onder verschillende omstandigheden veranderen:
 
  
#Is het hart fysiek gedraaid en wijst deze dus niet meer naar linksonder dan draait de hartas in dezelfde richting als het hart mee. Bijv. het hart wijst naar rechts dan is de ORS-vector ook naar rechts gelocaliseerd.  
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==Abnormal heartaxis==
#In het geval van een hypertrofisch hart, zal door grotere elektrische activiteit de vector in die richting meedraaien (naar hypertrofisch weefsel toe).  
+
[[Image:left_axis_dev.jpg|thumb| Heartaxis deviation to the left in case of an inferior infarct. Left anterior hemi Block is a common cause. A left axis is between -30 and -90 degrees. The axis is -30 degrees.]]
#Het omgekeerde geldt voor weefsl dat is geinfarceerd. Hier worden namelijk geen elektrische prikkels meer voortgeleid. Dit weefsel draagt niet meer bij aan het ontstaan van vectoren. De QRS-vector draait dan van het geinfarceerde weefsel af.
+
[[Image:right_axis_dev.jpg|thumb| Heartaxis deviation to the right in right ventricular load, as in COPD or pulmonary embolism. A right axis is between +90 and +180 degrees. In this case the axis is +135 degrees]]
#Bij geleidingsproblemen draait de hartas ook vaak. Stel dat de rechter kamer, later depolariseert dan de linker door een vertraging in het geleidingsweefsel van de rechter kamer. Als de linker kamer klaar is met contraheren is de rechter nog bezig. Het signaal van de linker kamer maskeert nu niet meer dat van de rechter. Alle nog aanwezige electrische activiteit gaat naar rechts en de hartas draait dus ook naar rechts.
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The direction of the vector can changes  under different circumstances:
 +
 +
#When the heart itself is rotated (right ventricular overload), obviously the axis turns with it.  
 +
#In case of ventricular hypertrophy, the axis will deviate by the bigger electrical activity and the vector will turn towards the hypertrophied tissue.  
 +
#Infarcted tissue is electrically dead. No electrical activity is registered and the QRS vector turns away from the infracted tissue
 +
#In conduction problems, the axis deviates too. When the right ventricle depolarizes later than the left ventricle, the axis will turn to the right (RBBB). This is because the right ventricle will begin the contraction later and therefore will also finish later. In a normal situation the vector is influenced by the left ventricle but now only by the right ventricle.
  
 
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==Examples of a left heartaxis==
 
==Examples of a left heartaxis==
[[Image:LHA.png|thumb| Linker hartas]]
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[[Image:LHA.png|thumb| Left heartaxis]]
[[Image:LAHB.png|thumb| Linker anterior hemiblok]]
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[[Image:LAHB.png|thumb| Left anterior hemi block]]
 
*[[Conduction delay#LAFB| left anterior fascicular block]]
 
*[[Conduction delay#LAFB| left anterior fascicular block]]
 
*[[Ischemia#Inferior|Inferior myocardial infarction]]
 
*[[Ischemia#Inferior|Inferior myocardial infarction]]
 
*[[Hypertrophy|Left ventricular hypertrophy]]
 
*[[Hypertrophy|Left ventricular hypertrophy]]
*Pacemakerritme
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*Pacemaker rhythm
 
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== Examples of a right heartaxis ==
 
== Examples of a right heartaxis ==
[[Image:rightaxis.jpg|thumb| Rechter hartas]]
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[[Image:rightaxis.jpg|thumb| Right heartaxis]]
 
*[[Hypertrophy| Right ventricular hypertrophy]]
 
*[[Hypertrophy| Right ventricular hypertrophy]]
*Rechter ventrikelbelasting, bijvoorbeeld bij [[Overigen#Longembolie|longembolien]] of cor pulmonale (zoals bij COPD)
+
*Right ventricular load, for example [[Miscellaneous#Pulmonary_embolism|Pulmonary Embolism]] or Cor Pulmonale (as in COPD)
*Atriumseptumdefect, ventrikelseptumdefect
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*Atriumseptumdefect, ventricleseptumdefect
 
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Revision as of 18:31, 20 May 2007

Accuracy dispute This article or section is currently being developed or reviewed.
Some statements may be disputed, incorrect or biased.
Author(s) I.A.C. van der Bilt, MD
Moderator I.A.C. van der Bilt, MD
Supervisor
some notes about authorship

What is the electrical heartaxis?

The heartaxis indicates the average direction of the depolarization wave. A normal heartaxis, the picture shows an example, is between -30 and +90 degrees. In this example, the heartaxis is +45 degrees.
Heartaxis from the original publication of Einthoven. Reprinted from The Lancet, March 30 1912, Einthoven W., The Different Forms of The Human Electrocardiogram and Their Signification, 853-861, 1912, with permission from Elsevier

The electrical heartaxis is an average of all depolarizations in the heart. The depolarization wave begins in the right atrium and proceeds to the left and right ventricle. Because the left ventricle wall is thicker than the right wall, the arrow indicating the direction of the depolarization wave is directed to the left.

For a lot of people, this is a difficult concept. The theoretic part seems difficult but by doing it a lot, it will become clear.

How do you determine the electrical heartaxis

Hart axis.png
Hartasroset.png

When you average all electrical signals from the heart, you can indicate the direction of the average electrical depolarization with an arrow (vector). This is the heartaxis. Especially a change of the heartaxis or an extreme deviation can be an indication for pathology.

For example:

  • Biggest QRS deflection in lead I: the electrical activity is directed to the left (of the patient)
  • Biggest QRS deflection in lead AVF: the electrical activity is directed down.

This indicates a normal heartaxis. Usually, these two leads are enough to diagnose a normal heartaxis!

The biggest vector in the heart is from the AV-node in the direction of the ventricular depolarization. Under normal circumstances, this is directed left and down.(towards leads I and AVF). The position of the QRS vector is given in degrees. See the figure, the middle of the figure is the AV-node. A horizontal line towards the left arm is defined as 0 degrees.

A normal heartaxis is between -30 and +90 degrees.

Rule: biggest QRS deflection in I and II is an intermediate = normal heartaxis. So positive deflections in I and II indicates a normal heartaxis.


Interpretation

The interpretation of the electrical heartaxis has a few rules of thumb:

  • First, when a positive depolarization wave moves towards a positive electrode, a positive, upwards deflection is registered on the ECG.
  • Second, there are 4 quadrants where the QRS-vector can point to:
    • left upper quadrant --> left axis deviation (between -30º and -90º)
    • left lower quadrant --> normal (between -30º and 90º)
    • right below and right --> right axis deviation (between 90º and -150º)
    • right upper quadrant --> extreme axis (between -90º and -150º)

Example:

The QRS in lead I, will have a negative deflection in a right axis deviation. The vector is not directed towards the electrode. However, lead AVF will be positive, the vector is directed towards the electrode.

Heart-axis Simulator

To understand how the ECG changes in axis deviations, this excellent axis-simulator may be helpful: http://www.blaufuss.org/ECGviewer/indexFrame2.html

Iso-electrical

Note: When the depolarization is perpendicular on the lead, this is called iso-electrical. The QRS is neither positive nor negative.

Undetermined axis

When all extremity leads are biphasic, the axis is directed to the front or back, in a transverse plane. The axis is than undetermined.

Abnormal heartaxis

Heartaxis deviation to the left in case of an inferior infarct. Left anterior hemi Block is a common cause. A left axis is between -30 and -90 degrees. The axis is -30 degrees.
Heartaxis deviation to the right in right ventricular load, as in COPD or pulmonary embolism. A right axis is between +90 and +180 degrees. In this case the axis is +135 degrees

The direction of the vector can changes under different circumstances:

  1. When the heart itself is rotated (right ventricular overload), obviously the axis turns with it.
  2. In case of ventricular hypertrophy, the axis will deviate by the bigger electrical activity and the vector will turn towards the hypertrophied tissue.
  3. Infarcted tissue is electrically dead. No electrical activity is registered and the QRS vector turns away from the infracted tissue
  4. In conduction problems, the axis deviates too. When the right ventricle depolarizes later than the left ventricle, the axis will turn to the right (RBBB). This is because the right ventricle will begin the contraction later and therefore will also finish later. In a normal situation the vector is influenced by the left ventricle but now only by the right ventricle.


Examples of a left heartaxis

Left heartaxis
Left anterior hemi block


Examples of a right heartaxis

Right heartaxis


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