Ventricular tachycardia - Torsades de pointes

Question 1

what is ventricular tachycardia?

Answer 1

potentially life-threatening arrhythmia

originates in cardiac ventricles

Question 2

what causes ventricular tachycardia?

Answer 2

cardiac scars 
conduction disorders
drugs 
long-QT syndrome - congenital or acquired 
electrolyte imbalances 
ischaemic stroke 
intracranial haemorrhage 
endocrine disorders 
nutritional disorders 
can rarely occur in healthy individuals

Question 3

what cardiac scars can cause ventricular tachycardia?

Answer 3

cardiomyopathy
myocardial infarction
iatrogenic
post-op

Question 4

conduction disorders

Answer 4

e.g. cardiomyopathy

disruption of conduction pathways

Question 5

what drugs cause ventricular tachycardia?

Answer 5

antiarrhythmics 
antibiotics 
antidepressants 
antipsychotics 
anticonvulsants

Question 6

which antiarrhythmics cause VT?

Answer 6

class Ia - quinidine and disopyramide 
class III - sotalol, amiodarone

Question 7

which antibiotics cause VT?

Answer 7

macrolides

fluoroquinolones

Question 8

which antidepressants cause VT?

Answer 8

most tricyclic and tetracyclic antidepressants

lithium

Question 9

which antipsychotics cause VT?

Answer 9

haloperidol

Question 10

which anticonvulsants cause VT?

Answer 10

felbamate

fosphenytoin

Question 11

what electrolyte imbalances cause VT?

Answer 11

hypokalemia
hypomagnesemia
hypocalcemia

Question 12

what is the most ECG abnormality after ischaemic stroke or intracranial haemorrhage?

Answer 12

QT prolongation

Question 13

what endocrine disorders cause VT?

Answer 13

hypothyroidism

Question 14

what nutritional disorders cause VT?

Answer 14

anorexia nervosa

Question 15

pathophysiology of VT

Answer 15

monomorphic VT
polymorphic VT
decreased cardiac output

Question 16

monomorphic VT

Answer 16

all QRS complexes look similar
increased automaticity
re-entry circuit

Question 17

what is a re-entry circuit?

Answer 17

myocardial scarring creates an area of poor electrical conduction so the impulse travels around the scar

Question 18

polymorphic VT

Answer 18

dissimilar QRS complexes
caused by abnormal ventricular repolarisation
e.g. long QT syndrome, drug toxicity and electrolyte abnormalities

Question 19

decreased cardiac output

Answer 19

asynchronous atrial and ventricular beats
rapid ventricular rhythm
decreased blood flow into the ventricle during diastole
decreased CO
haemodynamic compromise

Question 20

what are the clinical features of VT

Answer 20

often asymptomatic - especially if non-sustained

symptoms if sustained

Question 21

clinical features of sustained VT

Answer 21

palpitations
hypotension 
syncope
severe cases:
chest pain/pressure - in conjunction with MI 
cardiogenic shock
loss of consciousness 
progression to ventricular fibrillation 
sudden cardiac death

Question 22

what are the subtypes/variants of VF

Answer 22

torsades de pointes

Question 23

what is torsades de pointes?

Answer 23

polymorphic ventricular tachycardia with QRS complexes that appear to twist around the isoelectric line
can progress to life-threatening ventricular arrhythmia

Question 24

what causes torsades de pointes?

Answer 24

prolonged QT interval caused by congenital disease, electrolyte abnormalities and drugs

Question 25

treatment for torsades de pointes

Answer 25

defibrillation if haemodynamically unstable | IV magnesium sulfate if haemodynamically stable

Question 26

diagnosis of ventricular tachycardia

Answer 26

ECG - main holter monitor patient-activated event recorder echocardiography

Question 27

ECG VT findings

Answer 27

3 or more consecutive premature ventricular beats - widened QRS >120bpm = HR

Question 28

ECG findings sustained vs nonsustained

Answer 28

``` nonsustained = <30seconds sustained = >30 seconds ```

Question 29

ECG findings - morphology

Answer 29

``` monomorphic = all QRS complexes look similar polymorphic = QRS complexes are different ```

Question 30

other possible ECG findings

Answer 30

AV dissociation Fusion complex capture beats

Question 31

AV dissociation

Answer 31

no relationship between P waves and QRS complexes | ventricular rhythm is often faster than atrial rhythm

Question 32

Fusion complex

Answer 32

atrial and ventricular impulses occur simultaneously

Question 33

Capture beats

Answer 33

supraventricular impulse may reach AV node and produce a subsequent ventricular beat

Question 34

holter monitor

Answer 34

24-48 hour ambulatory monitor | useful for diagnosing intermittent VT which may not be present on a single ECG

Question 35

patient-activated event recorder

Answer 35

device to evaluate patient's heart rhythm during symptomatic episodes - can be manually initiated or automatic

Question 36

echocardiography

Answer 36

provides information about possible causes of VT

Question 37

common differential diagnosis

Answer 37

supraventricular tachycardia with aberrancy - RBBB, LBBB or wolff-parkinson-white

Question 38

signs and symptoms that suggest VT rather than SVT

Answer 38

over 35 year olds history of structural heart defects or past MI AV dissociation, fusion beats and capture beats

Question 39

signs and symptoms that suggest SVT with aberrancy rather than VT

Answer 39

BBB on prior ECG history of SVT evidence of wolff-parkinson-white

Question 40

what is SVT with aberrancy?

Answer 40

group of tachyarrhythmias that originate in the atria or AVN wide QRS complex due to conduction defects can be irregular or regular

Question 41

what is wolff-parkinson-white?

Answer 41

congenital condition intermittent tachycardia and ventricular pre-excitation pattern on ECG due to bundle of kent which connects the atria and ventricles, bypassing the AVN - delta wave and shortened PR interval

Question 42

treatment of VT

Answer 42

initial therapy and long-term therapy

Question 43

initial therapy for VT

Answer 43

different depending on whether patient is haemodynamically unstable or stable

Question 44

initial therapy is patient is hemodynamically unstable

Answer 44

VT with pulse = cardioversion VT without pulse = defibrillation advanced cardiac life support look for and address possible causes = electrolyte abnormalities and correct, medication induced QT prolongation

Question 45

initial therapy is patient is hemodynamically stable

Answer 45

antiarrhythmics cardioversion if medical therapy fails look for and address possible causes = electrolyte abnormalities, metabolic-induced QT prolongation

Question 46

which antiarrhythmics can be used to treat VT?

Answer 46

lidocaine procainamide amiodarone

Question 47

what electrolyte abnormalities cause VT?

Answer 47

hypokalaemia | correct as part of treatment

Question 48

medication-induced QT prolongation

Answer 48

remove any causative medication | use digoxin immune fragment antigen binding for digoxin toxicity

Question 49

long-term therapy for VT

Answer 49

intracardiac devices catheter ablation antiarrhythmics

Question 50

intracardiac devices

Answer 50

most effective treatment for reducing mortality from VT - used when VT doesn't respond to therapy

Question 51

catheter ablation

Answer 51

used when intracardiac devices cannot be tolerated or often receive intracardiac device shocks because of repeated VT