Ventricular Tachycardia
February 15th, 2021
On this page:Monomorphic Ventricular TachycardiaPolymorphic Ventricular TachycardiaTorsade de Pointes
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
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
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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