2.02 - Cardiomyopathies

Question 1

What is cardiomegaly?

Answer 1

Increase in cardiac weight or size

Question 2

What is hypertrophy?

Answer 2

thickened heart muscle due to increased cell size

Question 3

What is cardiac dilation?

Answer 3

Increase in size of heart chambers

Question 4

Describe the structure of cardiac muscle

Answer 4

Contractile myofilaments arranged regularly –> cross striations
Branching
Intercalated discs between cells –> rapid spread of excitation
Cell membrane (sarcolemma), calcium reservoir (sarcoplasmic reticulum), contractile elements (sarcomere)

Question 5

Describe intercalated discs

Answer 5

Specialised cellular junctions
Permit rapid spread of contractile stimuli due to areas of low electoral resistance. Necessary for simultaneous contraction of all fibres

Question 6

Describe the sarcoplasmic reticulum

Answer 6

Calcium storage. Slow calcium leak from SR and T tubules –> automatic contractions

Question 7

Describe the sarcomere

Answer 7

Intracellular contractile unit (responsible for striated appearance). Contraction of the cardiac muscles occur by sliding of the actin filaments towards the centre of the sarcomere

Question 8

What is cardiomyopathy?

Answer 8

Cardiomyopathy is a disease of the heart
muscle associated with cardiac dysfunction in the absence of valve disease, congenital, coronary artery disease, hypertension etc.
o Primary: Heart only
o Secondary: Systemic disease

Question 9

What are some of the common presentations of cardiomyopathy?

Answer 9

Syncope
Heart failure
Sudden Death
Thromboembolism
Chest pain
Arrhythmias
Fatigue
Shortness of breath

Question 10

How can cardiomyopathies be classified?

Answer 10

Cause (Primary, secondary, idiopathic)
Macroscopic (pathologic) appearance (most common method)
Genetic mutation / inheritance
Functional (diastolic failure, systolic failure)

Question 11

What are the functional consequences of diastolic heart failure?

Answer 11

Failure of the heart chambers to fill. Caused by restriction of filling during diastole such as in thickening of any of the layers of the heart

Question 12

What are the functional consequences of systolic heart failure?

Answer 12

Decreased cardiac output
Often associated with dilated chambers.
Heart is not able to contract properly and get that SV out

Question 13

What are the four main primary cardiomyopathies?

Answer 13

Dilated Cardiomyopathy (DCM)
Hyperthrophic Cardiomyopathy (HCM)
Restrictive Cardiomyopathy (RCM)
Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)

Question 14

What are some secondary causes of cardiomyopathies?

Answer 14

Cardiac infections (viruses - coxsackie B, enterovirus)
Metabolic (hypo- hyperthyroidism, hyper- hypokalemia, vitamin deficiency)
Infiltrative (sarcoidosis)
Toxins (alcohol, arsenic, lithium, chronic renal failure)
Arrhythmia induced
Immunological (post transplant rejection, autoimmune)
Pregnancy, peri-partun, post-partum
Stress (takotsubo)

Question 15

What are the primary causes of cardiomyopathies?

Answer 15

Genetic mutations causing defects in cytoskeleton, contractile protiens or mitochondrial oxidative phosphorylation can lead to cardiomyopathies
Frequently inherited in an autosomal dominant fashion

Question 16

Describe Dilated Cardiomyopathy (DCM)

Answer 16

90% of all cardiomyopathies
Progressive cardiac dilatation with or without hypertrophy (4-chamber)
Systolic dysfunction
Presentation with congestive heart failure/ arrhythmia

Question 17

What are the main causes of DCM?

Answer 17

Alcohol 
Pregnancy (can sometimes be reversible)
Infections
Genetic (likely due to mutations in genes for cytoskeletal proteins
Idiopathic

Question 18

Describe the macroscopic appearance of DCM

Answer 18

Large, globular, flabby, heavy heart with dilated chambers (especially ventricles)
Ventricle wall thickness normal or increased

Question 19

What are some complication of DCM

Answer 19

Mural thrombi – embolism
Myocardial ischaemia
Ventricular arrhythmias
Congestive heart failure
Functional valvular dysfunction / incompetence

Question 20

Describe Hypertrophic/Obstructive Cardiomyopathy (HOCM)

Answer 20

1/500 incidence
Genetic causes
Left ventricular outflow tract obstruction due to asymmetric septal hypertrophy
Most common cause of sudden cardiac death in young adults

Question 21

Describe the genetics of HOCM

Answer 21

Virtually all are inherited
Autosomal dominant resulting from mutations coding sarcomeric proteins
Most common is beta myosin heavy chain

Question 22

Describe the macroscopic appearance of HOCM

Answer 22

Massively enlarged and heavy
LV hypertrophy, especially asymmetric septal hypertrophy, often prominent in sub aortic region
Atrial dilation due to impaired diastolic filling
Thickened septal vessels

Question 23

Describe the histological appearance of HOCM

Answer 23

Extreme myocyte hypertrophy and myocyte disarray
Individual myocytes whorled, tangled and pinwheel configuration
Disarray of contractile elements within cells
Interstitial fibrosis

Question 24

List some complications of HOCM

Answer 24

Arrhythmias: atrial fibrillation, ventricular arrhythmias
Symptoms: syncope/dizziness (especially during exercise)
Mural thrombi
Myocardial ischaemia
Sudden death

Question 25

Describe Restrictive Cardiomyopathy (RCM)

Answer 25

Least common
Stiff ventricles causing increased intraventricular pressure and impaired ventricular filling during diastole
Important to differentiate from constrictive pericarditis

Question 26

What are some causes of RCM

Answer 26

Idiopathic
Genetic (sarcomeric proteins)
Associated with infiltrative myocardial diseases (amyloidosis, haemochromatosis, sarcoidosis)
Endomyocardial diseases (thickening of the endocardial layer causing stiffening)

Question 27

Describe the histology os RCM

Answer 27

Ventricular wall thickness and cavity size often normal
Atrial dilatation with thrombi may be seen and heart weight may be increased
Myocardium is firm
Interstitial fibrosis

Question 28

Describe Arrhythmogenic Right Ventricular Cardiomopathy (ARVC)

Answer 28

Gross thickening of dilated RV wall and loss of myocytes and fibrofatty replacement
Present with: right ventricular failure, ventricular arrhythmias, sudden death (exertional)
Aeitiology not clear