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| {{SI}}
| | #redirect:[[Wide complex tachycardias]] |
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| {{CMG}}
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| __NOEDITSECTION__
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| '''Associate Editor-In-Chief''' Jiwon Kim
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| == Differential Diagnosis of Tachycardia with Wide QRS Complex ==
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| # A regular tachycardia with a rate of 120 to 200 BPM with a QRS duration of .12 seconds or longer may be due to: <br>
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| #* Paroxysmal VT
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| #* Supraventricular tachycardia with abnormally wide QRS
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| #*:# Sinus tachycardia
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| #*:# SA nodal reentrant tachycardia
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| #*:# Paroxysmal atrial tachycardia
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| #*:# Intraatrial reentrant tachycardia
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| #*:# Atrial flutter with 2:1 conduction and occasional 1:1 conduction
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| #*:# AV nodal reentrant tachycardia
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| #*:# Automatic junctional tachycardia
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| #*:# AV reentrant tachycardia using a bypass tract
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|
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| == Differential Diagnosis of Wide QRS Complexes ==
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| #Aberrant ventricular conduction <br>
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| #Preexisting left or right bundle branch block <br>
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| #Preexisting nonspecific IVCD <br>
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| #Antegrade conduction through the bypass tract in patients with WPW <br>
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| == Clues to the Diagnosis of VT ==
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| # Morphology of Premature Beats During Sinus Rhythm: <br> | |
| #* Previous EKG may show preexisting IVCD.
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| #* If PVCs are present, and if the morphology of the arrhythmia is the same, then it is likely to be ventricular in origin.
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| #* If there are PACs with aberrant conduction, then the origin of the arrhythmia may be supraventricular.
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| # Onset of the Tachycardia: <br>
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| #* Diagnosis of SVT made if the episode is initiated by a premature P wave.
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| #* If the paroxysm begins with a QRS then the tachycardia may be either ventricular or junctional in origin.
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| #* If the first QRS of the tachycardia is preceded by a sinus p wave with a PR interval shorter than that of the conducted sinus beats, the tachycardia is ventricular.
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| # AV Dissociation: <br>
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| #* Although is highly suggestive of VT, it may also be seen in junctional tachycardias with retrograde block.
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| # Morphology of the QRS Complexes and QRS Axis: <br>
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| #* 80 to 85% of aberrant beats have a RBBB pattern, but ectopic beats that arise from the LV have a similar morphology.
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| #* The finding of a positive or negative QRS complex in all precordial leads is in favor of ventricular ectopy.
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| #* A QRS duration of > .14 seconds (A Wellens criterion)
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| #* Left axis deviation (A Wellens criterion)
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| #* A monophasic or biphasic RBBB QRS complex in V1. But none of their patients with SVT had a preexisting RBBB. Therefore, this finding is of limited importance. (A Wellens criterion)
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| # Akhtar studied 150 patients with a wide complex tachycardia. The following were helpful in the diagnosis of VT: <br>
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| #* all patients with VT had a QRS duration > 120 msecond.
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| #* QRS > .14 with a RBBB, QRS > .16 with LBBB.
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| #* V1 - V6 all show a positive deflection.
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| #* QRS axis between -90 and + 180 degrees.
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| #* The QRS complexes have a LBBB but the QRS axis is rightward.
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| #* In patients with preexisting bundle branch block, there is a change in the QRS pattern during the tachycardia.
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| # Capture beats: <br>
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| #* Rare, but one of the strongest pieces of evidence in favor of VT.
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| #* Aberrancy rarely follows a beat of such short cycle length.
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| # Fusion beats: <br>
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| #* Rare but also strongly suggests VT.
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| # Vagal Stimulation: <br>
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| #* VT is not affected by vagal stimulation.
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| #* May terminate reentrant arrhythmias
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| # Atrial pacing: <br>
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| #* A pacing wire is placed in the RA and the atrium is stimulated at a rate faster than the tachycardia.
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| #* If ventricular capture occurs and the QRS is normal in duration, then one can exclude the possibility of aberrant conduction.
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| # His bundle recording: <br>
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| #* In SVT, each QRS is preceded by a His bundle potential.
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| #* In VT there is no preceding His deflection.
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| #* The retrograde His deflection is usually obscured by the much larger QRS complex.
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| {| class="wikitable" font-size="75%"
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| |- style="text-align:center;background-color:#6EB4EB;"
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| |+'''An overview of ventricular tachycardias''', follow the [[media:wideQRS_tachycardia_flow.png|wide complex tachycardia flowchart]]
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| |-
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| !
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| !example
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| !regularity
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| !atrial frequency
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| !ventricular frequency
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| !origin (SVT/VT)
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| !p-wave
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| !effect of adenosine
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| |-
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| | colspan="8" style="text-align:left;background-color:#cfefcf;" | '''Wide complex (QRS>0.12)'''
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| |-
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| ! [[Ventricular Tachycardia]]
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| | [[Image:vt_small.svg|200px]]
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| | regular (mostly)
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| | 60-100 bpm
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| | 110-250 bpm
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| | ventricle (VT)
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| | [[AV-dissociation]]
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| | no rate reduction (sometimes accelerates)
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| |-
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| ! [[Ventricular Fibrillation]]
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| | [[Image:vf_small.svg|200px]]
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| | irregular
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| | 60-100 bpm
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| | 400-600 bpm
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| | ventricle (VT)
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| | [[AV-dissociation]]
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| | none
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| |-
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| ! [[Ventricular Flutter]]
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| | [[Image:vflutt_small.svg|200px]]
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| | regular
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| | 60-100 bpm
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| | 150-300 bpm
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| | ventricle (VT)
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| | [[AV-dissociation]]
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| | none
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| |-
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| ! [[Accelerated Idioventricular Rhythm]]
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| | [[Image:aivr_small.svg|200px]]
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| | regular (mostly)
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| | 60-100 bpm
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| | 50-110 bpm
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| | ventricle (VT)
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| | [[AV-dissociation]]
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| | no rate reduction (sometimes accelerates)
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| |-
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| ! [[Torsade de Pointes]]
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| | [[Image:tdp_small.svg|200px]]
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| | regular
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| | 150-300 bpm
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| | ventricle (VT)
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| | [[AV-dissociation]]
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| | no rate reduction (sometimes accelerates)
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| |-
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| ! [[Bundle-branch re-entrant tachycardia]]*
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| | [[Image:bb_reentry_small.svg|200px]]
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| | regular
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| | 60-100 bpm
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| | 150-300 bpm
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| | ventricles (VT)
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| | [[AV-dissociation]]
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| | no rate reduction
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| |-
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| |colspan="8"|*) Bundle-branch re-entrant tachycardia is extremely rare
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| |}
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| == Differential Diagnosis of Wide QRS Complex Tachycardia ==
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| # The following favor the diagnosis of VT: <br>
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| #* AV dissociation
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| #* RBBB with QRS > .14, or LBBB with QRS > .16
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| #* QRS axis in RUQ between -90 and +180 degrees
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| #* Positive QRS in all the precordial leads (V1-V6)
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| #* LBBB with a rightward axis
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| #* LBBB with the following QRS morphology
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| #*:# R wave in V1 or V2 > 0.03 second
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| #*:# any Q wave in V6
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| #*:# Onset of the QRS to nadir of the S wave in V1 > 0.06 seconds
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| #*:# Notching of the S wave in V1 or V2
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| #* Capture beats, fusion beats
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| #* QRS morphology identical to that of premature ventricular beats during sinus rhythm
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| == Clinical Correlation ==
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| # Most patients with VT have organic heart disease. <br>
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| # Post MI VT is associated with a doubling of the risk of death. <br>
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| # This was an a risk factor independent of poor LV function. <br>
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| # VT can be seen with reperfusion, but an accelerated idioventricular rhythm is more common. <br>
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| # Digoxin intoxication is a common cause. Other antiarrhythmics, phenothiazines, TCAs, and pheochromocytoma may also cause this. <br>
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| # Cardiac catheterization, DC countershock, following repair of congenital lesions, and the hereditary QT prolongation are all associated with VT. <br>
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| {{Electrocardiography}}
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| [[Category:Electrophysiology]]
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| [[Category:Cardiology]]
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