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CARDIO TEST 2 > Lecture 10: Cardiomyopathies – Sarcomeric Disease > Flashcards

Lecture 10: Cardiomyopathies – Sarcomeric Disease Flashcards

1
Q

What are cardiomyopathies?

A

Heterogenous group of dysfunctional conditions

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2
Q

What identifies a cardiomyopathy?

A

Anatomical conditions

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3
Q

What is cardiomyopathy caused by?

A

Disease, drugs, genetics, unknown

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4
Q

What is dilated cardiomyopathy and what is it caused by?

A

Chamber enlargement, caused by alcohol toxicity, virus or genetic metabolic abnormality

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5
Q

What is restrictive cardiomyopathy and what is it caused by?

A

Rigid ventricles, cannot fill or relax properly, caused by fibrosis and tumour

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6
Q

What is FHC?

A

Familial hypertrophic cardiomyopathy

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7
Q

What is characteristic of FHC and what is it caused by?

A

Disrupted myocyte geometry due to fibrosis

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8
Q

What is the risk of FHC?

A

1/500

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9
Q

What mode of inheritance does FHC follow?

A

Autosomal dominant

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10
Q

How many sarcomere mutations and how many myofilament genes in FHC?

A

> 450 mutations in 13 myofilament genes

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11
Q

How long is the cardiac sarcomere?

A

2um

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12
Q

What does titin do?

A

Springs thick filament to ends or sarcomere and moves it back and forwards to actin

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13
Q

What are the components of the thin filament?

A

Actin, troponin, tropomyosin

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14
Q

What are the components of myosin?

A

ELC - essential light chain

RLC - regulatory light chain

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15
Q

What happens when there is low calcium?

A

Actin myosin interaction blocked by TnT interaction

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16
Q

What happens when there is high calcium?

A

Calcium binds to TnC, pulls away TnI, allows tropomyosin to move away, actin and myosin cross bridge

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17
Q

What is the most commonly mutated sarcomeric protein and what are its features?

A

Beta myosin heavy chain
MYH7 gene
212 mutations
Affects 25-35% of people

18
Q

What is a point missense mutation?

A

Different codon - change one aa in proton

19
Q

What is a point nonsense mutation?

A

No aa coded (stop codon)- truncated protein

20
Q

What is a frameshift mutation?

A

Insertion/deletion of a base - very different protein made

21
Q

What is a poison peptide?

A

Affected allele makes defective protein - messes with normal allele protein

22
Q

What is haploinsufficiency?

A

Normal allele doesn’t produce enough protein, imbalance in sarcomere components

23
Q

What is a splice error?

A

Exons not assembled normally due to a mutation in the splice acceptor site

24
Q

What happens when there is an MHC mutation?

A

Heart expresses beta and alpha forms, beta expressed in early development and failure and is more commonly mutated, if beta and alpha are mutated there is hyper contractility

25
Q

What happens when troponin is mutated?

A

Increased calcium sensitivity

26
Q

What happens when actin is mutated?

A

Reduced sliding velocity and myosin affinity

27
Q

What happens when there is a structural mutation in the myofilaments?

A

Altered mechanical integrity, problems with energy production

28
Q

What are the four regions of myosin mutation?

A

ATP binding site, actin binding pocket, hinge and lever, filament backbone

29
Q

What happens in the FHC primary phenotype?

A

Increased calcium sensitivity, systolic function and ATP utilisation at low calcium levels.

Decreased diastolic function.

30
Q

What happens in the FHC secondary phenotype?

A

Inefficient oxygen consumption, hypertrophy gene induction, reduced SR calcium loading, sarcomere trauma and necrosis

31
Q

What gene in myosin leads to 70-80% function loss?

A

ArgGln

32
Q

What gene in FHC is linked with increased LV hypertrophy?

A

ACE DD

33
Q

Under what age is FHC the most common cause of death?

A

35

34
Q

When does 70% of SCD in FHC occur?

A

During or immediately after exercise

35
Q

What is SCD due to?

A

Ventricular triggered arrhythmia or conduction arrhythmia

36
Q

What effect does exercise have on SCD?

A

Moderate exercise delays and strenuous exercise accelerates

37
Q

What percentage of SCD does FHC account for?

A

33%

38
Q

What is the male to female ratio of SCD?

A

M 9: F 1

39
Q

What % of athletes have LV wall thickness as seen in FHC?

A

2%

40
Q

What % of athletes have LV cavity size as seen in FHC?

A

15%

CARDIO TEST 2 (10 decks)

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