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Ventricular Tachycardia

February 15th, 2021

Monomorphic Ventricular Tachycardia

Monomorphic VT is a focal or reentrant ventricular rhythm that requires rapid assessment and management, due to its risk of haemodynamic instability and collapse.
  • Look For

  • Heart rate >100bpm
  • Regular rhythm (RR interval)
  • Broad QRS complexes >120ms
  • Monomorphic Ventricular Tachycardia
A left bundle branch morphology classically suggests a right ventricular focus of VT, while a right bundle morphology pattern suggests a left ventricular focus. A septal focus may manifest as either a left or right bundle branch morphology.
To find out how to distinguish VT from SVT with aberrancy, read the section called 'distinguishing VT and SVT with aberrancy'.
  • Classification

  • Nonsustained VT - three or more ventricular beats at a rate of >100bpm, lasting less than 30 seconds, without haemodynamic instability
  • Sustained VT - a ventricular rhythm at a rate of >100bpm, lasting at least 30 seconds or with haemodynamic instability
  • Mechanisms

  • Monomorphic VT occurs most commonly in the context of a macro-reentrant pathway in a structurally abnormal heart. The rhythm may also be caused by a focal arrhythmogenic ventricular focus.
  • Causes of Monomorphic Ventricular Tachycardia

  • Myocardial infarction
  • Cardiomyopathy
  • Congestive cardiac failure

Polymorphic Ventricular Tachycardia

Polymorphic VT is a wide complex tachycardia with multiple QRS complex morphologies. This most commonly refers to torsade de pointes, however PVT also present in patients with acute myocardial infarction.
  • Look For

  • Heart rate >100bpm
  • Irregular rhythm
  • Broad QRS complexes of varying amplitude and morphology
  • Causes of Polymorphic Ventricular Tachycardia

  • Torsade de pointes - due to prolonged QT
  • Non-torsades polymorphic VT - most commonly due to coronary ischaemia / infarction
Polymorphic VT other than torsade de pointes will have a normal QTc once reverted to sinus rhythm.

Torsade de Pointes

Torsades is a polymorphic VT that occurs as a result of a prolonged QT interval.
  • Look For

  • Polymorphic ventricular tachycardia with 'twisting' around the isoelectric line
  • Prolonged QT interval once reverted to sinus rhythm
  • Torsade de Pointes
  • Causes of Prolonged QT

  • Congenital

  • LQTS1 (triggered by exercise)
  • LQTS2 (triggered by stress and loud noises)
  • LQTS3 (triggered by sleep)
  • Others - LQTS4-6, Jervell and Lange-Nielsen syndrome
  • Drugs

  • Antiarrhythmics - amiodarone, sotalol, procainamide, quinidine
  • Antidepressants - amitryptiline, dothiepine, citalopram, escitalopram
  • Antipsychotics - risperidone, haloperidol, clozapine, droperidol, chlorpromazine
  • Antiemetics - ondansetron, domperidone
  • Macrolides - azithromycin, clarithromycin, erythromycin
  • Quinolones - ciprofloxacin, moxifloxacin
  • Antifungals - fluconazole, ketoconazole
  • Antimalarials - chloroquine, mefloquine
  • Anaesthetic gases - halothane, sevoflurane
  • Methadone
  • Others

  • Hypokalaemia
  • Hypomagnesaemia
  • Hypocalcaemia
  • Severe hypothermia
  • Severe bradycardia - sick sinus syndrome, complete heart block
  • Cardiovascular disease - tako-tsubo cardiomyopathy, MI, CCF
  • Cerebrovascular disease - intracranial / subarachnoid haemorrhage, stroke
  • Hypothyroidism
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