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B2 - Pathology > 0721 - pathology of cardiomyopathy - AHF > Flashcards

0721 - pathology of cardiomyopathy - AHF Flashcards

1
Q

What is the weight of a normal heart?

A

250 - 350 grams.

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2
Q

Define cardiomegaly.

A

Increase in cardiac weight or size (relative to sex and weight-matched tables).

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3
Q

Define hypertrophy.

A

Thickened heart muscle due to increased cell size.

  • free LV wall > 14 mm
  • septum > 14 mm
  • posterior RV wall > 4 mm
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4
Q

Define dilation.

A

Increase in size of heart chambers.

  • ventricle > 40 mm
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5
Q

Outline the features of cardiac muscle (relative to skeletal and smooth muscle).

A
  • intermediate between smooth and skeletal muscle
  • contractile myofilaments arranged regularly to form cross-striations
  • cardiac myocytes are branching
  • intercalated discs
  • innervated by ANS (i.e. involuntary)
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6
Q

Describe cardiac muscle histology.

A

Cardiac myocytes:

  • are elongated, branching cells
  • contain:
    • cell membrane (sarcolemma)
    • Ca2+ reservoir (sarcoplasmic reticulum)
    • contractile elements (sarcomere)
    • abundant mitochondria
    • central, single nucleus
  • join together to form a syncytium
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7
Q

What is the functional significance of the intercalated discs?

A

They are specialised cellular junctions specific to cardiac muscle that permit rapid spread of excitation due to areas of low electrical resistance, which is necessary for simultaneous contraction of all fibres.

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8
Q

What are the 3 types of membrane contacts of intercalated discs?

A
  • fascia adherens: site of actin filament insertion
  • desmosomes: anchorage for intermediate filaments
  • gap junctions: pores with low electrical resistance enabling ion and molecule transfer between the cells, allowing for coordinated contraction
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9
Q

Explain how the Frank-Starling mechanism can lead to a pathologic condition.

A

Although greater stretch = great contraction (and hence greater SV, and hence greater CO), this is only so to a certain point, the optimal length. Beyond the optimal length, SV decreases.

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10
Q

Is heart failure associated with an increase or decrease in inotropy?

A

Decreased inotropy (contraction force) and hence SV.

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11
Q

Define cardiomyopathy.

A

A disease of the heart muscle associated with cardiac dysfunction in the absence of valvular, congenital or coronary artery disease, hypertension, etc.; cardiomyopathies divided into:

  • primary: heart only affected
  • secondary: systemic disease that affects the heart in a prominent way
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12
Q

How may a Px with cardiomyopathy present?

A
  • sudden death
  • syncope (clue that syncope due to a heart problem: poor exercise tolerance, pre-syncope palpitations, dyspnoea on exertion)
  • heart failure
  • thromboembolism (due to reduced contraction, blood flow through heart sluggish)
  • chest pain
  • arrhythmias (can be caused by cardiomegaly)
  • fatigue
  • dyspnoea
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13
Q

How can cardiomyopathies be classified?

A
  • by cause: primary, secondary, idiopathic
  • by pathologic appearance
  • by genetic mutation/inheritance: but most have diverse genetic causes
  • by function: diastolic failure, systolic failure
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14
Q

Outline the functional consequence of diastolic failure.

A
  • failure of filling
  • caused by restriction of filling during diastole, typically by thickening or stiffening of any of the layers of the heart (endocardium, myocardium, pericardium) of one or both atria
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15
Q

Outline the functional consequence of systolic failure.

A
  • decreased CO
  • often associated with dilated chambers, particularly LV
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16
Q

How does WHO classify cardiomyopathies?

A

Primary:

  • dilated cardiomyopathy (DCM)
  • hypertrophic cardiomyopathy (HCM)
  • restrictive cardiomyopathy (RCM)
  • arrhythmogenic right ventricular cardiomyopathy (ARVC)
  • (unclassified - left ventricular noncompaction, mitochondrial, etc.)

Secondary:

  • cardiomyopathies secondary to systemic conditions
17
Q

What are some causes of cardiomyopathy?

A
  • cardiac infections
  • metabolic
    • hyper/hypothyroidism
    • hyper/hypokalaemia
    • vitamin deficiency
    • haemochromatosis
    • malnutrition
    • obesity (fat is very vascular, to compensate, heart must increase in size)
  • infiltrative (i.e. disease infiltrates heart muscle)
    • sarcoidosis
  • toxins
    • alcohol
    • cobalt
    • arsenic
  • neuromuscular
    • amyloidosis
  • immunological
    • myocarditis
    • post-transplant rejection
    • autoimmune diseases
18
Q

Describe the generalised histology of cardiomyopathy.

A

Most cardiomyopathies do not have specific findings; general features include:

  • hypertrophic myocytes
  • enlarged nuclei
  • stretched, irregular and attenuated myocytes present
  • variable interstitial and endocardial fibrosis and scarring (geographic scarring typically MI, diffuse scarring typically a cardiomyopathy)
19
Q

What is the most common type of cardiomyopathy?

A

Dilated cardiomyopathy.

20
Q

Describe dilated cardiomyopathy.

A
  • progressive cardiac dilatation ± hypertrophy (in all 4 chambers)
  • systolic and diastolic dysfunction
  • presents with congestive heart failure/arrhythmia
  • main causes
    • alcohol or other toxins
    • pregnancy (can be reversible)
    • infections
    • genetics (25 - 35%, usually due to mutations in genes for cytoskeletal proteins)
    • idiopathic
  • large, globular, flabby, heavy heart with dilated chambers (especially ventricles)
  • ventricular wall thickness decreased, normal or increased with mural thrombi (thrombi that adhere to the wall of a blood vessel)
  • no significant abnormality of coronary arteries or valves
21
Q

List some conditions that mimic dilated cardiomyopathy.

A
  • ischaemic heart disease
  • valvular heart disease (especially regurgitative valves)
  • infiltrative disorders (haemochromatosis, amyloid, sarcoidosis)
22
Q

List some complications of dilated cardiomyopathy.

A
  • mural thrombi, embolism
  • myocardial ischaemia
  • ventricular arrhythmias
  • congestive heart failure
  • functional valvular dysfunction/incompetence
23
Q

Describe hypertrophic obstructive cardiomyopathy (aka hypertrophic cardiomyopathy).

A
  • most cases genetic (disorder of the genes (e.g. beta myosin heavy chain) related to structure or function of sarcomeric proteins)
  • hallmark = LV outflow tract obstruction due to asymmetric septal hypertrophy, often prominent in subaortic region

impaired diastolic filling (atrial dilation)

  • thickened septal vessels
  • extreme myocyte hypertrophy
  • myocyte disarray (myocytes not logically ordered)
  • most common cause of sudden cardiac death in young adults
  • most Px diagnosed at autopsy
24
Q

List some complications of hypertrophic obstructive cardiomyopathy.

A
  • mural thrombi
  • myocardial ischaemia
  • arrhythmias (atrial fibrillation, ventricular arrhythmias)
  • sudden death
  • syncope
  • (a lot of the symptoms related to dynamic obstruction; remove some of the septum to remove the obstruction)
25
Q

Describe restrictive cardiomyopathy.

A
  • least common type
  • stiff ventricles causing increased intraventricular pressure and impaired ventricular filing during diastole
  • ventricular wall thickness and cavity size often normal
  • atrial dilation with thrombi may be present
  • heart weight may be increased
  • firm myocardium
  • diffuse interstitial fibrosis
  • any layer of the heart that is thickened or poorly compliant can mimic restrictive cardiomyopathy, so important to differentiate, especially from constrictive pericarditis
  • causes
    • idiopathic
    • genetic
    • associated with distinct infiltrative myocardial diseases (e.g. amyloidosis, haemochromatosis, sarcoidosis)
  • endomyocardial diseases (thickening of endocardial layer, causing impaired filling and stiffening of the ventricles)
26
Q

What is endomyocardial fibrosis?

A

An idiopathic disorder of the tropical and subtropical regions that is characterised by the development of restrictive cardiomyopathy; endocardium layer becomes thickened.

27
Q

What is cardiac amyloidosis?

A

A clinical disorder caused by extracellular deposition of insoluble fibrils (can occur in multiple organs); when cardiac, it is a progressive disorder resulting in early death due to congestive heart failure and arrhythmias.

28
Q

Describe arrhythmogenic right ventricular cardiomyopathy.

A
  • fibrofatty replacement of RV and subepicardial region of LV
  • Px at high risk for ventricular tachyarrythmias and sudden death
  • gross thinning of dilated RV wall with loss of myocytes and fibrofatty replacement
29
Q

What is left ventricular non-compaction?

A

A relatively rare congenital condition that results from arrest of the normal compaction process of the myocardium during foetal development.

30
Q

Idiopathic hypertrophic subaortic stenosis (IHSS) is typical of:

A. hypertrophic cardiomyopathy

B. dilated cardiomyopathy

C. restrictive cardiomyopathy

A

A.

31
Q

Genetic defects in sarcomeric proteins (beta myosin heavy chain) as opposed to cytoskeletal proteins are more characteristic of:

A. hypertrophic cardiomyopathy

B. dilated cardiomyopathy

C. restrictive cardiomyopathy

A

A.

32
Q

All of the following cause restrictive cardiomyopathy except:

A. alcohol

B. amyloidosis

C. hypereosinophilic syndrome

D. radiation

E. sarcoidosis

A

A.

33
Q
A

B2 - Pathology (15 decks)

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