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RACP Written 2018 > Cardiology - QT Channelopathies > Flashcards

Cardiology - QT Channelopathies Flashcards

1
Q

When do you do genetic testing?

A
  • ANY patient with strong suspicion
  • Family hx
  • Asymptomatic with QTc>500ms

CONSIDER if QTc >480ms

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2
Q

What channelopathies result from mutations in SCN5A?

A

SCN5A encodes a Na channel on Ch3

GAIN: LQT3
LOSS: Brugada and Lenegres

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3
Q

What channelopathies result from mutations in KCNQ1?

A

KCNQ1 encondes K channel on Ch11

GAIN: Familial AF and SQTS
LOSS: LQT1

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4
Q

What channelopathies result from mutations in KCNH2?

A

KCNH2 encodes K channel on Ch7

GAIN: SQTS
LOSS: LQT2

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5
Q

What does SCN5A encode?

A

SCN5A encodes Na channel on Ch 3

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6
Q

What does KCNQ1 encode?

A

KCNQ1 encodes K channel on Ch 11

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7
Q

What does KCNH2 encode?

A

KCNH2 encodes K channel on Ch7

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8
Q

Antiarrythmics that cause long QT?

A

ANTI-ARRYTHMICS:

  • Class IA: quinidine / procainamide
  • Class III: sotolol / amiodarone
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9
Q

Antibiotics/Infection Drugs that cause long QT?

A

Macrolides: erythromycin, clarithromycin and azithromycin

Fluoroquinolones: levofloxacin and moxifloxacin

Bactrim
Clindamycin
Pentamidine
Chloroquine

Antifungals: ketoconazole / intraconazole
Antivirals: amantadine

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10
Q

Antihistamines that cause long QT?

A

Terfenedine

Diphenhydramine

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11
Q

Antipsychotics that cause long QT?

A

Haloperidol
Ziprasidone
Tricyclics and Tetracycline antidepressants

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12
Q

Other medications that cause long QT?

A
  • Cholinergic antagonists: cisapride / organophosphates
  • Citrate (ie post massive blood transfusion)
  • Cocaine
  • Methadone
  • Fluoxetine
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13
Q

Which electrolyte abnormalities cause long QT?

A

Hypokalaemia
Hypomagnesaemia
Hypocalcaemia

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14
Q

Which endocrine conditions cause long QT?

A 
Hypothyroidism
HyPERparathyroidism
Pheochromocytoma
HyPERaldosteronism
Hypothermia
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15
Q

Which intracranial causes cause long QT?

A 
SAH
Thalamic haematoma
CVA
Encephalitis
Head injury
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16
Q

Which nutritional disorders cause long QT?

A 
Anorexia nervosa
Starvation
Liquid protein diet
Gastroplasty and ileojujunal bypass
Coeliac disease
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17
Q

Definition of a long QTc?

A

Females >460ms

Males >440ms

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18
Q

Of LQT1, LQT2 and LQT3 what proportion of Long QT syndromes do they make?

A 
LQT1 = 45%
LQT2 = 45%
LQT3 = 7%
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19
Q

What is the mutation in LQT1

A

Mutation in K channel
Autosomal DOMINANT heterozygotic

Mutation in either:
KVLQT1 or KCNQ1 on Ch11

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20
Q

If someone has the homozygous mutation seen in LQT1 what do they have?

A

LQT1 is a mutation in either KVLQT1 or KCNQ1 on Ch11.
It is heterozygous autosomal dominant.

If they are homozygous then JERVELL-LANG-NIELSEN syndrome

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21
Q

What is the mutation in LQT2?

A

Mutation in K channel
Autosomal DOMINANT of either:
HERG or KCNH2 genes on Ch7

22
Q

What mutation in LQT3?

A

Mutation in Na channel

Autosomal DOMINANT of SCN5A on Ch3

23
Q

What is the Romano Ward Syndrome?

A

Autosomal DOMINANT
VT and QTc prolongation

Mutation in: ANK2 / KCNE1 / KCNE2 / KCNQ1 / SCN5A

24
Q

What is the Jervell-Lang-Nielsen Syndrome?

A

Autosomal RECESSIVE
VT and QTc prolongation
PLUS SENSORINEURAL HEARING LOSS

Mutation in KCNE1 or KCNQ1

25
Q

Jervell-Lang-Nielsen and Romano-Ward result in which cardiac abnormalities?
How do you tell them apart?

A

JVN is Autosomal RECESSIVE
And associated with sensorineural deafness

Romanoward is Autosomal DOMINANT

They both result in VT and QTc prolongation

26
Q

What triggers LQT1?

A

Exercise, swimming, sudden exposure of face to cold

27
Q

What triggers LQT2?

A

Emotion and loud noises

28
Q

What triggers LQT3?

A

Sleep

29
Q

Which Long QT Syndrome is triggered by Exercise, swimming, sudden exposure of face to cold

A

LQT1

30
Q

Which LQTS is triggered by Emotion and loud noises

A

LQT2

31
Q

Which LQTS is triggered by sleep

A

LQT3

32
Q

What classifies a Long QT Syndrome as HIGH risk?

A

If QTc >500ms and:

  • LQT1
  • LQT2
  • Male LQT3
33
Q

What classifies a Long QT Syndrome as INTERMEDIATE risk?

A

If QTc>500ms AND female LQT3

or

If QTc <500 and:

  • Female LQT2
  • Female LQT3
  • Male LQT3
34
Q

What classifies a Long QT Syndrome as LOW risk?

A

If QTc <500 and:

  • Male LQT2
  • LQT1
35
Q

If you are LQT1 what risk are you?

A

Low risk

36
Q

If you are LQT2 what risk are you?

A

FEMALE:
If QTc <500 then intermediate
If QTc >500 then high

MALE:
If QTc <500 then low
If QTc >500 then high

37
Q

If you are LQT3 what risk are you?

A

FEMALE: Intermediate

MALE:
If QTc <500 then intermediate
If QTc >500 then high

38
Q

How do you manage Long QT Syndrome?

A
  • IV magnesium if torsades
    • Beta blocker
  • prevents cardiac events in 70%
  • propranolol and nadolol most use
  • greatest benefit in LQT1

ICD (**UNLESS low risk and no history of VT)

Avoid competitive sports and medications that prolong QT

NO ROLE for PPM

39
Q

Which Betablocker must be avoided in Long QT Syndrome?

A

Sotalol (can exacerbate the QTc prolongation)

40
Q

Where do beta blockers have the greatest benefit in Long QT syndrome?

A

In LQT1

41
Q

Short QT Syndrome:

Definition and mutation

A

Short QTc <350ms

Autosomal DOMINANT gain of function mutation in K channel

42
Q

Short QT Syndrome:

Clinical features:

A

HIGH risk of sudden cardiac death

Also associated with:
AF
Polymorphic VT

43
Q

Management of short QT syndrome

A

ICD in EVERYONE

44
Q

Non-genetic causes of long QT?

A
  • Hypokalaemia
  • Hypomagnesaemia
  • Hypocalcaemia
  • Hypothermia
  • Myocardial ischaemia
  • Post cardiac disease
  • Raised ICP
  • Drugs
45
Q

Antipsychotic drugs that prolong QT?

A 
Chlorpromazine
Haloperidol
Droperidol
Quetiapine
Olanzapine
Amisulpride
46
Q

Antiarrythmics that prolong the QT?

A

Type 1A:

  • quinidine
  • procainamide
  • disopyramide

Type 1C:
- flecainide

Type III:

  • sotolol
  • amiodarone
47
Q

Tricyclic Antidepressants that prolong the QT?

A 
Amitryptiline
Imipramine
Doxepin
Nortryptyline
Desipramine
48
Q

Other antidepressants (not TCAs) that prolong the QT?

A

Citalopram and escitalopram
Venlafaxine
Bupropion
Moclobemide

49
Q

Antihistamines that prolong the QT?

A

Loratadine

Terfanidine

50
Q

Other drugs (not psych or antihistamines or arrythmics) that prolong the QT?

A

Chloroquine
Hydroxychloroquine
Quinine
Macrolides: erythromycin and clarithromycin

51
Q

Non-genetic causes of short QT?

A

Hypercalcaemia

Digoxin

RACP Written 2018 (167 decks)

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