Flashcards in Arrythmias: Ventricular tachyarrhythmias Deck (28)
List the types of Ventricular tachyarrhythmias
-Sustained ventricular tachycardia
-Torsades de pointes
Normal heart ventricular tachycardia
Non-sustained ventricular tachycardia
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?
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
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
-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
-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?
What ECG changes are seen with ventricular fibrillation?
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
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?
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
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
What is the treatment of acquired long QT syndrome?
Correct electrolyte disturbances
Stop causative drugs
Maintain atrial or ventricular pacing
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