Ventricular tachycardia: Difference between revisions

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[[image:vt.jpg|right|thumb|450px|This is an example of a VT. There are lots of different types but if it's a broad QRS and over 120 bpm, it's a VT.]]
[[image:vt.jpg|right|thumb|300px|'''This is an example of a VT (click for a bigger version)'''. There are lots of different types but if it's a broad QRS and over 120 bpm, it's a VT.]]
===Definition===
===Definition===
This is a [[broad-complex tachycardia]] (QRS >120ms/3 small squares) which originates in the ventricles.
This is a [[broad-complex tachycardia]] (QRS >120ms/3 small squares) which originates in the ventricles.
====Torsades de pointes====
[[image:torsades.jpg|right|thumb|300px]]
A form of VT where the amplitude of the QRS complex varies. Important as it is likely to lead to [[VF]].


===Epidemiology===
===Epidemiology===
[[image:common.jpg]]Really common and dangerous, particularly in [[coronary artery disease]].
[[image:common.jpg]]Really common and dangerous, particularly in [[coronary artery disease]].
===Pathophysiology===
===Pathophysiology===
There are three different types of VT:
[[image:torsades.jpg|right|thumb|300px|Torsades de pointes - note the changes in amplitude.]]
*Fascicular - uncommon; associated with structural heart defects; from left bundle branch; short QRS complexes (0.11-0.14s); QRS complexes look like [[RBBB]]
There are four different types of VT:
*Right ventricular outflow tract - right axis deviation; [[LBBB]] pattern; provoked by [[catecholamine]] release, sudden changes in heart rate, exercise; responds to alpha-blockers and calcium antagonists.
*'''Fascicular''' - uncommon; associated with structural heart defects; from left bundle branch; short QRS complexes (0.11-0.14s); QRS complexes look like [[RBBB]]
*Polymorphic - looks like [[Torsades de pointes]] (QT interval normal in sinus rhythm); similar to [[AF]]; can lead to [[cardiogenic shock]] and [[VF]].
*'''Right ventricular outflow tract''' - right axis deviation; [[LBBB]] pattern; provoked by [[catecholamine]] release, sudden changes in heart rate, exercise; responds to alpha-blockers and calcium antagonists.
*[[Torsades de pointes]]
*'''Polymorphic''' - looks like [[Torsades de pointes]] (QT interval normal in sinus rhythm); similar to [[AF]]; can lead to [[cardiogenic shock]] and [[VF]].
*'''Torsades de pointes''' - A form of VT where the amplitude of the QRS complex varies. Important as it is likely to lead to [[VF]].


===Risk Factors===
===Risk Factors===
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===Investigations===
===Investigations===
====ECG====
====ECG====
Differences between VT andd [[SVT]]:
Differences between VT and [[SVT]]:
*VT more likely than SVT - AV dissociation (lack of synchronicity between atria and ventricles); fusion beat (where normal and ectopic ventricular beats coincide); QRS > 40ms; [[ECG|rS pattern]] (small rise, big fall, back to normal instead of QRS complex) in V1.
*VT more likely than SVT - AV dissociation (lack of synchronicity between atria and ventricles); fusion beat (where normal and ectopic ventricular beats coincide); QRS > 40ms; [[ECG|rS pattern]] (small rise, big fall, back to normal instead of QRS complex) in V1.
*SVT more likely than VT - [[RBBB]] pattern; varying bundle branch block; qR pattern (no initial drop in QRS complex) in V1; ectopic P wave preceding arrhythmia.
*SVT more likely than VT - [[RBBB]] pattern; varying bundle branch block; qR pattern (no initial drop in QRS complex) in V1; ectopic P wave preceding arrhythmia.
====Bloods====
====Bloods====
*[[U+Es]] - particularly calcium, potassium and magnesium.
*[[U+Es]] - particularly calcium, potassium and magnesium.
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===Management===
===Management===
*'''Pulseless VT''' - treat like [[VF]]
*'''Pulseless VT''' - treat using [[advanced life support]]
*'''Unstable VT''' - synchronised [[cardioversion]]. May result in [[VF]]. '''Amiodarone''' is first-line for [[haemodynamically unstable]] VT. Deal with electrolyte disturbances too.
*'''Unstable VT''' - synchronised [[cardioversion]]. May result in [[VF]]. '''Amiodarone''' is first-line for [[haemodynamically unstable]] VT. Deal with electrolyte disturbances too.
*'''Stable VT''' - treat with IV lidocaine and cardioversion
*'''Stable VT''' - treat with IV lidocaine, or other [[class 1b antiarrhthmic]] and cardioversion
*'''Refractory VT''' - amiodarone.
*'''Refractory VT''' - amiodarone.
*'''Torsades de pointes'''
**''Acute'' - magnesium; then, beta 1-adrenergic agonist (isoprotenerol), temporary [[pacing]]
**''Long-term'' - beta-blockers (congenital, ''not'' acquired), [[pacing]]


===Prognosis===
===Prognosis===
Generally favourable.
Generally favourable.

Latest revision as of 10:00, 23 May 2010

This is an example of a VT (click for a bigger version). There are lots of different types but if it's a broad QRS and over 120 bpm, it's a VT.

Definition

This is a broad-complex tachycardia (QRS >120ms/3 small squares) which originates in the ventricles.

Epidemiology

Common.jpgReally common and dangerous, particularly in coronary artery disease.

Pathophysiology

Torsades de pointes - note the changes in amplitude.

There are four different types of VT:

  • Fascicular - uncommon; associated with structural heart defects; from left bundle branch; short QRS complexes (0.11-0.14s); QRS complexes look like RBBB
  • Right ventricular outflow tract - right axis deviation; LBBB pattern; provoked by catecholamine release, sudden changes in heart rate, exercise; responds to alpha-blockers and calcium antagonists.
  • Polymorphic - looks like Torsades de pointes (QT interval normal in sinus rhythm); similar to AF; can lead to cardiogenic shock and VF.
  • Torsades de pointes - A form of VT where the amplitude of the QRS complex varies. Important as it is likely to lead to VF.

Risk Factors

Clinical Features

Presents with features of ischaemic heart disease or haemodynamic compromise. Chest pain, palpitations, dyspnoea, dizziness, syncope and possibly symptoms of heart failure.

Investigations

ECG

Differences between VT and SVT:

  • VT more likely than SVT - AV dissociation (lack of synchronicity between atria and ventricles); fusion beat (where normal and ectopic ventricular beats coincide); QRS > 40ms; rS pattern (small rise, big fall, back to normal instead of QRS complex) in V1.
  • SVT more likely than VT - RBBB pattern; varying bundle branch block; qR pattern (no initial drop in QRS complex) in V1; ectopic P wave preceding arrhythmia.

Bloods

  • U+Es - particularly calcium, potassium and magnesium.
  • Levels of therapeutic drugs like digoxin
  • Trop T for MI
  • CXR - due to possibility of heart failure

Management

  • Pulseless VT - treat using advanced life support
  • Unstable VT - synchronised cardioversion. May result in VF. Amiodarone is first-line for haemodynamically unstable VT. Deal with electrolyte disturbances too.
  • Stable VT - treat with IV lidocaine, or other class 1b antiarrhthmic and cardioversion
  • Refractory VT - amiodarone.
  • Torsades de pointes
    • Acute - magnesium; then, beta 1-adrenergic agonist (isoprotenerol), temporary pacing
    • Long-term - beta-blockers (congenital, not acquired), pacing

Prognosis

Generally favourable.

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