Arrythmias: Ventricular tachyarrhythmias Flashcards Preview

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Flashcards in Arrythmias: Ventricular tachyarrhythmias Deck (28)
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List the types of Ventricular tachyarrhythmias

-Sustained ventricular tachycardia
-Ventricular fibrillation
-Torsades de pointes
Normal heart ventricular tachycardia
Non-sustained ventricular tachycardia
Ventricular ectopics


Define cardiac channelopathies

Congenital disorders due to mutations that affect cardiac ion channels and electrical activity in the heart.

Includes: Brugada syndrome, congenital long QT, short QT, catecholaminergic polymorphic ventricular tachycardia (CPVT), and idiopathic VF


Define sustained ventricular tachycardia

A ventricular tachycardia (usually 120-220 bpm) with >30s duration.


How may sustained ventricular tachycardia present?

Pre-syncope (dizziness)
Cardiac arrest

May be remarkably well tolerated in some patients

Cannon 'a' waves in neck (due to AV dissociation), and variable intensity of S1


What ECG changes are seen with sustained ventricular tachycardia?

Broad QRS: often >140ms
-80% of broad complex tachycardias are VT
-Concordant QRS in all chest leads suggestive of VT

Regular R-R intervals
AV dissociation
Capture beats: intermittent narrow QRS due to normal ventricular activation via AVN.
Fusion beats: hybrid complex as supraventricular and ventricular impulse coincide.


Outline the treatment of sustained ventricular tachycardia

Treat any identifiable underlying causes

Haemodynamically unstable:
-Emergency DC cardioversion
-May use adjunctive amiodarone and lidocaine

Haeomodynamically stable (non-idiopathic):
-Amiodarone: preferred if LV dysfunction, or
-Lidocaine: history or suspected ischaemia
-If unsuccessful: DC cardioversion

Haemodynamically stable idiopathic sustained VT:
-Electrophysiology specialist advice


Distinguish between SVT with BBB and VT

VT is more likely in the following:
-Very broad QRS
-AV dissociation
-Bifid QRS with taller first peak in V1
-Deep S wave in V6
-Concordant QRS in all chest leads


Define ventricular fibrillation

Very rapid irregular activation of the ventricles with no mechanical effect (pulseless).


How does ventricular fibrillation present?

Rapid unconsciousness
Respiration ceases
Cardiac arrest


What ECG changes are seen with ventricular fibrillation?

Broad QRS
Shapeless rapid oscillations
No organised complexes


What is the treatment of ventricular fibrillation?

DC cardioversion with basic and advanced life support

ICD if unrelated to an MI, due to high risk of recurrent cardiac arrest and sudden death.


Define Brugada syndrome

A hereditary sodium channelopathy resulting in idiopathic VF (no structural disease).

Carries a high risk of sudden cardiac death, and is prevalent amongst young males in SEA.


Outline the presentation of Brugada syndrome

Sudden death during sleep*
Resuscitated cardiac arrest

May be asymptomatic


How is Brugada syndrome diagnosed?

Characteristic Type 1 ECG finding + clinical criteria

Type 1 ECG: Coved ST elevation in at least two of V1-V3, with T wave inversion

Clinical criteria: one of
-Documented VF or polymorphic VT
-FHx of sudden cardiac death <45yr
-Coved ECG in family
-Inducible VT with Class I antiarrhythmics
-Nocturnal agonal respiration


What is the treatment for Brugada syndrome?



Name 3 causes of acquired long QT syndrome

Bradycardia: provokes QT prolongation and Torsades
Acute MI

Hypokalaemia, hypomagnesaemia, hypocalcaemia

Quinidine, procainamide (Ia)
Sotalol, amiodarone (III)
Tricyclic antidepressants: Amitriptyline, clomipramine
-FGAs: Haloperidol, chlorpromazine
-SGAs: Olanzapine, quetiapine, risperidone etc.
Macrolides: Erythromycin, clarithromycin


Define prolonged QT interval

QTc >450ms (male) or >460ms (female) on ECG


Describe the ECG appearance of Torsades de Pointes

QRS complexes twisting around isoelectric line


How can Torsades de Pointes present?

Recurrent syncope*

Usually terminates spontaneously, but may degenerate to VF, causes sudden death


Outline the treatment of Torsades de Pointes

IV magnesium sulphate

Correct any electrolyte disturbances
Stop causative drugs
Atrial or ventricular pacing to maintain heart rate


Name 3 risk factors for Torsades de Pointes

Congenital long QT syndrome
Female gender
Acquired long QT syndrome (causes of which include medications and electrolyte disorders such as hypokalaemia and hypomagnesemia)
Baseline electrocardiographic abnormalities
Renal or liver failure (such as alcoholic liver disease)


What is the management of congenital long QT syndrome?

Lifestyle: avoid drugs that prolong QT interval, prevent electrolyte abnormalities (diarrhoea, vomiting, metabolic conditions, imbalanced weight-loss diets), restrict stressors that may predispose to arrhythmias.

Beta blockers* (reduces mortality from 21% to 0.5%)
ICD: documented cardiac arrest

Family screening


What is the treatment of acquired long QT syndrome?

Correct electrolyte disturbances
Stop causative drugs
Maintain atrial or ventricular pacing
Magnesium sulphate


When is beta-blocker therapy mandatory in long QT syndrome?

All symptomatic patients
Asymptomatic with a QTc >470 ms


State 3 features in a history that would raise suspicion of a cardiac condition of genetic origin

FHx of fainting, cardiac events, sudden unexplained deaths, accidents, or drownings


How is QTc calculated?

QTc = QT interval / sq root of RR interval

Accurate for patients with normal heart rate (60-100)


How is long QT syndrome diagnosed?

At least one of the following:
1. Schwartz score of 3.5 or greater, in the absence of a secondary cause for QT prolongation
2. QTc of 500ms of greater in repeated 12-lead ECGs, in the absence of a secondary cause for QT prolongation
3. Pathogenic mutation in one of the LQTS genes


Name one indications for ICD in long QT syndrome

Documented cardiac arrest
Recurrent syncope while on beta-blocker therapy