Ectopic Complexes: Difference between revisions

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m (New page: =Ectopic beats= The pacemakercells in the sinusnode are not the only cells in the heart that can depolarize spontaneously. Actually all cardiomyoctyes have this capacity. The only reason w...)
 
 
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=Ectopic beats=
{{authors|
The pacemakercells in the sinusnode are not the only cells in the heart that can depolarize spontaneously. Actually all cardiomyoctyes have this capacity. The only reason why the sinusnode 'rules' is that it is the fastest pacemaker of the heart. From sinusnode to ventricle all healthy cardiomyocytes can function as a ectopic pacemaker. Ectopic pacemaker activity can originate from the atria (60-80 bpm), AV-node (40-60 bpm) and the ventricles (20-40 bpm). So, as the sinus rate drops (e.g. during atrial infarction), other cells can take over. The configuration of ectopic beats or extrasystoles, as seen on the ECG, reveals its origin, whether they are [[#Atrial premature beats|atrial]], nodal or [[#Premature ventricular beats(PVB) / Venticular extrasystoles (VES)|ventrical]].
|mainauthor= [[user:Drj|J.S.S.G. de Jong]]
 
|moderator= [[user:Drj|J.S.S.G. de jong]]
===Ectopic pacemakers===
|supervisor=
* ''Atrial ectopic pacemaker:'' frequency 50-60bpm
* ''Nodal ectopic pacemaker'' frequency 50bpm
* ''Ventricular ectopic pacemaker'' frequency 30-40bpm
 
===Atrial rhythm===
{{Arrhythmias|
| name = Atrial Rhythm
| locatieImage = [[Image:ECG_atrial_rhythm_now_sr.png|250px]]
| atrial_frequency = 50-100 bpm
| ventricular_frequency = 1:1
| regularity = regular
| origin = atrial
| p_wave = present, but different from sinus rhythm
| adenosine = slows down
| example = [[Image:ECG_atrial_rhythm_now_sr.png |250px| Atrial rhythm. In this example the sinus node stopped pacing due to ischemia during an atrial infarction. The p-wave is positive in I, negative in III and AVF. The atrial pacemaker is thus situated at the bottom of the right atrium, close to the AV node.]]
}}
}}
Atrial rhythm resembles sinusrhythm, but origins from a different atrial focus. It can be recognised by the abnormal configuration of the p-wave. Often the p-wave is negative in AVF, as is seen in the example.
[[Image:Rhythm_premature.png|thumb| An [[Atrial_Premature_Complexes|atrial]] with a noncompensatory pause.]]
{{clr}}
[[Image:Rhythm_ventricular_premature.png|thumb|A [[Premature ventricular beats(PVB) / Venticular extrasystoles (VES)|ventricular extrasystole]] with a compensatory pause]]
[[Image:pacemaker_rates.svg|thumb|Mycoardial cells with pacemaker activity]]
The pacemaker cells in the sinus node are not the only cells in the heart that can depolarize spontaneously. Actually all cardiomyoctyes have this capacity. The only reason why the sinus node 'rules' is that it is the fastest pacemaker of the heart. All healthy cardiomyocytes from the sinus node to the ventricles can function as ectopic pacemakers. Ectopic pacemaker activity can originate from the atria (60-80 bpm), AV-node (40-60 bpm) and the ventricles (20-40 bpm). So, as the sinus rate drops (e.g. during atrial infarction), other cells can take over. The configuration of ectopic complexes, or extrasystoles, as seen on the ECG, reveals its origin, whether they are [[Atrial_Premature_Complexes|atrial]], nodal or [[ves|ventrical]].


===Wandering Pacemaker===
==Ectopic pacemakers==
[[Image:Rhythm_WAP.png|thumb| Wandering pacemaker. Every p-wave is different and thus has a different origin.]]
{| class="wikitable"
When several pacemakers are competing, p-waves with different origins and thus configurations occur. The rhythm is slightly different from beat to beat.  
|+ '''Heart cells with pacemaker activity'''
! Celltype || Frequency || QRS width (*)
|-
| ''SA node'' (not ectopic)|| 60-100 bpm || narrow
|-
| ''Atrial || 55-60 bpm  || narrow
|-
| ''AV Nodal ectopic pacemaker'' ||  45-50 bpm || narrow
|-
| ''His bundle'' ||  40-45 bpm || narrow
|-
| ''Bundle branch'' ||  40-45 bpm || narrow or wide
|-
| ''Purkinje cells'' ||  35-40 bpm|| wide
|-
| ''Myocardial cells'' ||  30-35 bpm|| wide
|-
|}
(*) QRS width can only be narrow if the conduction system downstream is normal (i.e. no bundle branch block)


'''note''' If the heart rate increases to above 100bpm, it is called ''Multifocal Atrial Tachycardia''. Possible causes are hypoxia, COPD and medication such as digoxin.
==Compensatory or noncompensatory pause==
{{clr}}
[[File:comppause.svg|thumb|A ladder diagram showing a non-compensatory pause following an atrial premature beat that resets the sinus node and fully compensatory pause following a ventricular premature beat that does not reach the sinus node.]]
The duration of the interval following a premature complex can help in the differentiation of a atrial or ventricular premature complex.


===Premature atrial complex / atrial extrasystole===
===Non-compensatory pause, following an atrial premature complex===
[[Image:Rhythm_premature.png|thumb| A premature atrial complex (PAC). (In this example the atrial p-wave is difficult to discern).]]
If a sinus complex is followed by an atrial premature complex, the electrical activity of the atrial premature complex can enter the sinus node and reset its timing. If the sinus rate were, for example, 60/min, the reset pacemaker cells will restart firing after 1 full second had passed. The time from the extra complex to the next QRS complex in this example is thus 1 second. The sequence "normal sinus complex" - "atrial premature complex" - "normal sinus complex" will therefore be shorter than the 3 seconds it would have taken if the premature complex had not occurred. This is called a non (fully) compensatory pause.  
[[Image:Bes.png|thumb| A premature atrial complex (PAC) with evident negative p-wave]]
Sometimes the electrical activity of the atrial premature complex cannot enter the sinus node due to refractoriness of the sinus node (if the interval between previous sinus complex and atrial premature complex is short) or due to electrical block to enter the sinus node (as in sinus nodal disease).  
Premature atrial complexes origin from an ectopic pacing region in the atria. The result is a p-wave with often a different morphology as the preceding ones.  
{{clr}}


===AV-nodal complexes===
===Fully compensatory pause, following a ventricular premature complex===
Originate from the AV node. The AV node fires before the sinusnode. The ECG shows a QRS complex with a comparable morphology as during sinus rhythm as these extra beats are conducted further through the normal conduction system. When the extra follows very soon after the earlier one, [[aberrant conduction]] can occur.
The electrical activity of a ventricular premature complex is usually not conducted through the AV node towards the atria. The sinus node will not be reset. If the next sinus complex finds the AV nodal tissue still refractory (and thus not conducting,) there will be a pause until the next sinus complex follows. The interval between the premature ventricular complex and the next sinus complex will be longer (longer than 1 second in the above sample of a heart rate of 60/min). This is called a fully compensatory pause. With the use of a caliper, the preceding sinus rate can be tracked beyond the ventricular premature complex. This is a telltale sign of a ventricular premature complex without retrograde conduction.
The extra beat does not have a p-wave in front of it. Sometimes an inverted p-wave can be seen in or at the end of the QRS complex.


===Ventricular premature beat (VPB) / Ventricular extrasystole (VES)===
==Parasystole==
[[Image:Rhythm_ventricular_premature.png|thumb| The arrow indicates a ventricular extrasystole (VES).]]
[[Image:parasystole_12lead.jpg|thumb|An example of parasystole on a 12 lead ECG]]
A VPB is an ectopic beat that origins from the ventricles. VPBs are hardly conducted by the specialised conduction system and therefore are broad. The QRS width is at least > 0.12 seconds, but often very broad at around 0.16-0.20 seconds.  
[[Image:Paraystole_rhythmstrip.jpg|thumb|This rhythm strip shows clear parasystole. Here the origin of the ectopic beats is somewhat distal to the HIS bundle.]]
 
Parasystole is the phenomenon that results from two competing pacemakers in the heart. Usually a supraventricular and nodal/ventricular pacemaker compete. For example, sinus rhythm might be interfered with by ventricular ectopic beats. The basic rhythm in this example would be sinus rhythm with a rate of 60/min. Ectopic ventricular complexes can be seen interfering with this rate and rhythm. Parasystole is diagnosed when the ectopic complexes have a constant RR interval, e.g. 1500ms, resulting in a rate of 20 ventricular ectopic complexes per minute. [[Fusion complexes]] are often present as the two rhythms are dissociated.
Causes: e.g. ischemia, hypoxia, old scar tissue, idiopathic. 50% of healthy men have sporadic VPBs.
The origin of the VPB can be derived from its form. A LBTB-configured VPB originates in the right ventricle. A RBTB-configured VPB comes from the left ventricle. The QRS duration of a VPB is > 0.12 seconds and can be as wide as 0.16-0.20 seconds.
 
A sequence of three or more extrasystoles is called a [[#ventricular tachycardia|non-sustained ventricular tachycardia]].
 
If more than one VPB is present on the ECG, they can be:
*'''monomorphic''': all VPBs have the same configuration and thus have a mutual focus of origin.
*'''multiformic''': the complexes have different configurations.  
{{clr}}
{{clr}}


===Bigemini===
==Examples==
[[Image:Rhythm_bigemini.png|thumb|Bigemini: every sinus beat is followed by a ventricular extrasystole]]
*[[Atrial Rhythm]]
Every sinus beat is followed by a ventricular extrasystole.
*[[Wandering Pacemaker]]
{{clr}}
*[[Atrial Premature Complexes]]
 
*[[AV-nodal complexes]]
===Trigemini===
*[[Ventricular Premature Beats]]
Every second sinus beat is follow by a ventricular extrasystole.
{{clr}}

Latest revision as of 09:37, 26 September 2011

Author(s) J.S.S.G. de Jong
Moderator J.S.S.G. de jong
Supervisor
some notes about authorship
An atrial with a noncompensatory pause.
A ventricular extrasystole with a compensatory pause
Mycoardial cells with pacemaker activity

The pacemaker cells in the sinus node are not the only cells in the heart that can depolarize spontaneously. Actually all cardiomyoctyes have this capacity. The only reason why the sinus node 'rules' is that it is the fastest pacemaker of the heart. All healthy cardiomyocytes from the sinus node to the ventricles can function as ectopic pacemakers. Ectopic pacemaker activity can originate from the atria (60-80 bpm), AV-node (40-60 bpm) and the ventricles (20-40 bpm). So, as the sinus rate drops (e.g. during atrial infarction), other cells can take over. The configuration of ectopic complexes, or extrasystoles, as seen on the ECG, reveals its origin, whether they are atrial, nodal or ventrical.

Ectopic pacemakers

Heart cells with pacemaker activity
Celltype Frequency QRS width (*)
SA node (not ectopic) 60-100 bpm narrow
Atrial 55-60 bpm narrow
AV Nodal ectopic pacemaker 45-50 bpm narrow
His bundle 40-45 bpm narrow
Bundle branch 40-45 bpm narrow or wide
Purkinje cells 35-40 bpm wide
Myocardial cells 30-35 bpm wide

(*) QRS width can only be narrow if the conduction system downstream is normal (i.e. no bundle branch block)

Compensatory or noncompensatory pause

A ladder diagram showing a non-compensatory pause following an atrial premature beat that resets the sinus node and fully compensatory pause following a ventricular premature beat that does not reach the sinus node.

The duration of the interval following a premature complex can help in the differentiation of a atrial or ventricular premature complex.

Non-compensatory pause, following an atrial premature complex

If a sinus complex is followed by an atrial premature complex, the electrical activity of the atrial premature complex can enter the sinus node and reset its timing. If the sinus rate were, for example, 60/min, the reset pacemaker cells will restart firing after 1 full second had passed. The time from the extra complex to the next QRS complex in this example is thus 1 second. The sequence "normal sinus complex" - "atrial premature complex" - "normal sinus complex" will therefore be shorter than the 3 seconds it would have taken if the premature complex had not occurred. This is called a non (fully) compensatory pause. Sometimes the electrical activity of the atrial premature complex cannot enter the sinus node due to refractoriness of the sinus node (if the interval between previous sinus complex and atrial premature complex is short) or due to electrical block to enter the sinus node (as in sinus nodal disease).

Fully compensatory pause, following a ventricular premature complex

The electrical activity of a ventricular premature complex is usually not conducted through the AV node towards the atria. The sinus node will not be reset. If the next sinus complex finds the AV nodal tissue still refractory (and thus not conducting,) there will be a pause until the next sinus complex follows. The interval between the premature ventricular complex and the next sinus complex will be longer (longer than 1 second in the above sample of a heart rate of 60/min). This is called a fully compensatory pause. With the use of a caliper, the preceding sinus rate can be tracked beyond the ventricular premature complex. This is a telltale sign of a ventricular premature complex without retrograde conduction.

Parasystole

An example of parasystole on a 12 lead ECG
This rhythm strip shows clear parasystole. Here the origin of the ectopic beats is somewhat distal to the HIS bundle.

Parasystole is the phenomenon that results from two competing pacemakers in the heart. Usually a supraventricular and nodal/ventricular pacemaker compete. For example, sinus rhythm might be interfered with by ventricular ectopic beats. The basic rhythm in this example would be sinus rhythm with a rate of 60/min. Ectopic ventricular complexes can be seen interfering with this rate and rhythm. Parasystole is diagnosed when the ectopic complexes have a constant RR interval, e.g. 1500ms, resulting in a rate of 20 ventricular ectopic complexes per minute. Fusion complexes are often present as the two rhythms are dissociated.

Examples

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