Sinus Node Rhythms and Arrhythmias: Difference between revisions

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==Normal heart rhythm: sinus rhythm==
Please read the [[Introduction|introduction to the 7+2 step plan]] first.
[[Image:conduction_system_en.png|thumb|The conduction system handles the spreading of an electrical signal through the heart. The normal sinus rhythm begins in the sinus node and goes via the AV node to the His bundle where it splits via the right and left bundle branch.]]
[[Image:PQRS_origin_en.png|thumb| During normal sinus rhythm, every atrial contraction (P-wave) is followed by a ventricular contraction (QRS complex).]]
[[Image:normalSR.jpg|thumb|Normal sinus rhythm with a positive P-wave in I, II and AVF, and a biphasic P-wave in V1.]]
The normal heart rhythm is ''sinus rhythm''. That means that the rhythm has its origin in the sinus node, the heart's fastest physiological impulse generator.
The sinus node (SA) is located in the upper part of the wall of the right atrium. When the sinus node generates an electrical impulse, first the cells of the right atrium depolarise, then the cells of the left atrium, the AV (atrioventricular) node follows and at last the ventricles are stimulated via the His bundle.


With this knowledge it is quite simple to recognise normal sinus rhythm on the ECG.
The sinus node (SA) is located in the roof of the right atrium. It is the fastest physiological pacemaker. When the sinus node generates an electrical impulse, the surrounding cells of the right atrium depolarize. Then the cells of the left atrium, the AV (atrioventricular)node, follow, and at last the ventricles are stimulated via the His bundle.


;Criteria for normal sinus rhythm (see also [[Basics]]):
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With this knowledge it is quite simple to recognize normal sinus rhythm on the ECG.
 
{| class="wikitable"
!Criteria for normal sinus rhythm (see also [[Basics]]):
|-
|
*A [[P wave morphology]] P wave (atrial contraction) precedes every QRS complex
*A [[P wave morphology]] P wave (atrial contraction) precedes every QRS complex
*The rhythm is regular, but varies slightly while breathing
*The rhythm is regular, but varies slightly during respirations
*The frequency ranges between 60 and 100 beats per minute
*The rate ranges between 60 and 100 beats per minute
*The P waves maximum height is 2.5 mm in II and/or III
*The P waves maximum height at 2.5 mm in II and/or III
*The P wave is positive in I and II, and biphasic in V1
*The P wave is positive in I and II, and biphasic in V1
|}


These last two definitions will be discussed in the topic [[P wave morphology]].
As you can see, knowledge of [[Rate|heart rate]] and [[P wave morphology]] are necessary to determine the rhythm. We have put Rhythm as step 1 as it is of great importance. Arrhythmias include the most life-threatening ECG abnormalities. In most settings, however, the rhythm will be sinus.
Heart rhythms which are not sinus rhythm are [[arrhythmias]].


==Interpretation of the heart rhythm==
If the rhythm is not sinus, the '''[[Arrhythmias|Arrhythmias algorithm]]''' should be followed.
A good stepwise approach to interprete the heart rhythm is to follow these steps:
# '''Cherchez le P''', French for ''find the P waves''.
** Do you see P waves? Leads II and V1 are often most suitable to find P waves.
** What is the [[rate]] of the P waves?
** What is the [[P wave morphology]]?
# What is the relationship between P waves and QRS complexes?
** Is every P wave followed by a QRS complex? And every QRS preceded by a P wave? In short: is there a 1:1 relation between P waves and QRS complexes?
** What is the [[Conduction|PR interval]] and does it change?
# What is the ventricular [[heart rate]]?
# What is the [[QRS morphology]]?
# What is the clinical setting?


==Sinus arrhythmias==
==Sinus arrhythmias==
Some variants of sinusrhythm exist:
Some variants of sinus rhythm exist:
*[[Asystole]]
*[[Asystole]]
*[[Sinustachycardia|Sinustachycardia (>100 beats per minute)]]
*[[Sinustachycardia|Sinustachycardia (>100 beats per minute)]]
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*[[Sino-atrial_exit_block|Sino-atrial exit block]]
*[[Sino-atrial_exit_block|Sino-atrial exit block]]
*[[Sick Sinus Syndrome]]
*[[Sick Sinus Syndrome]]
*[[Sinus Arrhythmia]]
Arrhythmias are discussed in the [[Arrhythmias]] chapter.


If the heart rate exceeds 100 bpm, the [[Arrhythmias#Tachyarrhythmias|tachcyardia flow chart]] should be followed.
If the heart rate exceeds 100 bpm, the [[Arrhythmias#Tachyarrhythmias|tachcyardia flow chart]] should be followed.
{{clr}}
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==Examples==
==Examples==
[[Image:Normaal ecg.jpg|thumb| An example of normal sinus rhythm.]]
<gallery>
[[Image:Nsr.jpg|thumb| Another example of normal sinus rhythm.]]
Image:Normaal ecg.jpg|An example of normal sinus rhythm.
 
Image:Nsr.jpg|Another example of normal sinus rhythm.
</gallery>
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Latest revision as of 21:10, 14 January 2021

«Basics Step 2: Heart Rate»


Author(s) J.S.S.G. de Jong
Moderator I.A.C. van der Bilt
Supervisor
some notes about authorship

Please read the introduction to the 7+2 step plan first.

The sinus node (SA) is located in the roof of the right atrium. It is the fastest physiological pacemaker. When the sinus node generates an electrical impulse, the surrounding cells of the right atrium depolarize. Then the cells of the left atrium, the AV (atrioventricular)node, follow, and at last the ventricles are stimulated via the His bundle.

With this knowledge it is quite simple to recognize normal sinus rhythm on the ECG.

Criteria for normal sinus rhythm (see also Basics):
  • A P wave morphology P wave (atrial contraction) precedes every QRS complex
  • The rhythm is regular, but varies slightly during respirations
  • The rate ranges between 60 and 100 beats per minute
  • The P waves maximum height at 2.5 mm in II and/or III
  • The P wave is positive in I and II, and biphasic in V1

As you can see, knowledge of heart rate and P wave morphology are necessary to determine the rhythm. We have put Rhythm as step 1 as it is of great importance. Arrhythmias include the most life-threatening ECG abnormalities. In most settings, however, the rhythm will be sinus.

If the rhythm is not sinus, the Arrhythmias algorithm should be followed.

Sinus arrhythmias

Some variants of sinus rhythm exist:

Arrhythmias are discussed in the Arrhythmias chapter.

If the heart rate exceeds 100 bpm, the tachcyardia flow chart should be followed.

Examples

  • An example of normal sinus rhythm.

    An example of normal sinus rhythm.

  • Another example of normal sinus rhythm.

    Another example of normal sinus rhythm.


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