Ventricular Arrhythmias: Difference between revisions

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===Ventricular Tachycardia===
*[[Ventricular Tachycardia]]
{{Arrhythmias|
*[[Non-sustained VT]]
| name = Ventricular Tachycardia (VT or V-tach)
*[[Ventricular Flutter]]
| locatieImage =
*[[Ventricular fibrillation]]
| atrial_frequency = 60-100 bpm
*[[Torsade de pointes]]
| ventricular_frequency = 110-250 bpm
*[[Bundle-branch re-entrant tachycardia]]
| regularity = regular
| origin = ventricles
| p_wave = AV-dissociation
| adenosine = no rate reduction (can accelerate)
| example = An example of a polymorphic ventricular tachycardia [[Image:vtach.png|250px|Ventricular Tachycardia (VT or V-tach)]]
| example2 = Ventricular tachycardia on a 12 lead recording[[Image:12lead_vt1.jpg|thumb|Ventricular tachycardia of 140 bpm with a left bundle branch block and a left axis.]]
| animation = <flash>file=TenTusscherVT.swf|width=300|height=300|quality=best|align=right||</flash>
| animationdesc = This movie shows a computer model of ventricular tachycardia in the human heart. The VT in this example is initiated by a ventricular extrasystole and maintained by a re-entry rotor inferior in the left ventricle.<cite>tentusscher</cite> In reality, this is possibly not the etiology of VT in diseased hearts, however it is very illustrative. Read [[Copyright|this]] if you want to use this image in a presentation. [[Media:TenTusscherVT.swf|Link to the file / enlargement]]
}}
 
 
Ventricular tachycardia is defined as a sequence of three or more ventricular beats. The frequency must by higher than 100 bpm, mostly it is 110-250 bpm.
Ventricular tachycardias often origin around old scar tissue in the heart, e.g. after myocardial infarction. Also electrolyte disturbances and ischemia can cause ventricular tachycardias. The cardiac output is often strongly reduced during VT resulting in hypotension and loss of conciousness. VT is a medical emergency as it can deteriorate into [[#Ventricular fibrillation|Ventricular fibrillation]] and thus mechanical cardiac arrest.
 
Ventricular tachycardia can be catechorized as follows:
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====Non-sustained VT====
Non-sustained VT is defined three or more ventricular beats with a maximal duration of 30 seconds.
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====Sustained VT====
Sustained VT is defined as a VT of more than 30 seconds duration (or less if treated by electrocardioversion within 30 seconds).
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====Monomorphic VT====
All ventricular beats have the same configuration.
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====Polymorphic VT====
The ventricular beats have a changing configuration. The RR interval is 180-600 ms (comparable to a heart rate of 100-333 bpm).
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===Ventricular Flutter===
{{Arrhythmias|
| name = Ventricular Flutter
| locatieImage =
| atrial_frequency = 60-100 bpm
| ventricular_frequency = 150-300 bpm
| regularity = regular
| origin = ventricles
| p_wave = AV-dissociation
| adenosine = none
| example = An example of a ventricular flutter [[Image:Rhythm_flutter.png|250px|Ventricular Flutter]]
| example2 =
}}
Ventricular Flutter is mostly caused by re-entry with a frequency of 300 bpm. The ECG shows a typical sinusoidal pattern.  During ventricular flutter the ventricles depolarize in a circular pattern, which prevents good function. Most often this results in a minimal cardiac output and subsequent ischemia. Often deteriorates into [[#Ventricular fibrillation|ventricular fibrillation]].{{clr}}
 
===Ventricular fibrillation===
{{Arrhythmias|
| name = Ventricular Fibrillation (VF or V-fib)
| locatieImage =
| atrial_frequency = 60-100 bpm
| ventricular_frequency = 400-600 bpm
| regularity = irregular
| origin = ventricles
| p_wave = AV-dissociation
| adenosine = none
| example = An example of a ventricular fibrillation [[Image:Rhythm_ventricular_fibrillation.png|250px|Ventricular Fibrillation (VF or V-fib)]]
| example2 = Seven sinus beats are follow by a ventricular extrasystole (with R on T phenomenon), resulting in ventricular fibrillation [[Image:ECG_SR_to_VF_.jpg|250px|Initiation of ventricular fibrillation on a 12 lead ECG]]
| animation = <flash>file=TenTusscherVF.swf|width=250|height=250|quality=best|align=right||</flash>
| animationdesc = '''This movie shows a computer model of ventricular fibrillation in the human heart.<cite>tentusscher</cite>''' Read [[Copyright|this]] if you want to use this image in a presentation. [[Media:TenTusscherVF.swf|Link to the file / enlargement]]
}}
Ventricular fibrillation (VF or V-fib) is chaotic depolarisation of the ventricles. Mechanically this results in an arrested cardiac pump function and immediate death. VF can only be treated by immediate defibrillation. If you consider ventricular fibrillation in a conscious patient, than you should look for a technical problem with the ECG, eg. movement or electrical interference.
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===Torsade de pointes===
{{Arrhythmias|
| name = Torsade de Pointes (TdP)
| locatieImage =
| atrial_frequency = 60-100 bpm
| ventricular_frequency = 150-300 bpm
| regularity = regular
| origin = ventricles
| p_wave = AV-dissociation
| adenosine = no rate reduction (sometimes accelerates)
| example = An example of Torsade de Pointes. A normal sinus beat is followed by a ventricular extrasystole ('''short'''ly after the sinus beat), the compensatory pause results in a '''long'''er interval to the next beat. This longer beat therefore has a longer [[Conduction|QT interval]]. The next beat follows '''short'''ly therafter, withing the QT interval. Not all ventricular cells have been repolarized by that time and a ventricular arrhythmia results. This short-long-short sequence is typical for Torsades de pointes.[[Image:Rhythm_torsade.png|250px|Initiation of Torsade de Pointes (TdP) by a short-long-short sequence]]
| example2 = A twelve lead registration of Torsade de pointes. Reprinted with permission ''Copyright 2001 Texas Heart Institute'' <cite>Khan</cite> [[Image:12leadTorsade.jpg|250px|Torsade de Pointes (TdP) on a 12 lead ECG]]
}}
 
Torsade de pointes is a ventricular tachycardia associated with a [[Conduction#The_QT_time|long QT time]] on the resting ECG. Torsade de pointes is typically initiated by a short-long-short interval. A ventricle extrasystole (first beat: short) is followed by a compensatory pause. The following beat (second beat: long) has a longer QT interval. If the next beat follows shortly thereafter, ther is a good chance that this third beat falls within the QT interval, resulting in the R on T phenomenon and subsequent Torsades de pointes. During Torsades de pointes the ventricles depolarize in a circular fashion resulting in QRS complexes with a continuously turning heart axis around the baseline (hence the name ''Torsade de Pointes''). Read the chapter on the [[Long_QT_syndrome|Long QT syndrome]] for an list of causes.
 
There has been much debate in the ''Circulation'' journal among French and American scientist whether one should write ''Torsades de Pointes'' or ''Torsade de Pointes''. As for now ''Torsade'' is prefered (unless one sees rotations around more than one axis in one episode).<cite>Moise</cite>
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===Bidirectional VT===
A ventricular tachycardia with a QRS complex that alternates from beat to beat. Associated with [[Miscellaneous#Digoxin|digoxin intoxication]].
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===Bundle-branch re-entrant tachycardia===
{{Arrhythmias|
| name = Bundle-branch re-entrant tachycardia
| animation = <flash>file=TenTusscherBBR.swf|width=250|height=250|quality=best|align=right||</flash>
| animationdesc = '''This movie shows a computer model of bundle branch re-entrant tachycardia in the human heart. The VT in this example is initiated by a ventricular extrasystole and maintained by re-entry through the ventricular conduction system.<cite>tentusscher</cite> In reality, this is possibly not the etiology of VT in diseased hearts, however it is very illustrative.''' Read [[Copyright|this]] if you want to use this image in a presentation. [[Media:TenTusscherBBR.swf|Link to the FILE / enlargement]].
}}
Ventricular tachycardia resulting from re-entry in the His-Purkinje system, often with left bundle branch block configuration. Can occur in cardiomyopathy.
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Revision as of 19:53, 22 July 2007

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