cardiomyopathies

Question 1

what is the myocardium?

Answer 1

thickest layer of the heart. Composed of cardiac muscle§

Question 2

what is the functional unit of the myocardium?

Answer 2

sarcomere

Question 3

what is a cardiomyopathy?

Answer 3

any disease of the myocardium that can’t be explained by coronary artery narrowing or abnormal loading of ventricles

Question 4

what are primary cardiomyopathies?

Answer 4

genetic, mixed (genetic and nonmixed) or non-genetic (acquired) causes and are confined solely to the heart

Question 5

what are secondary cardiomyopathies?

Answer 5

affect the heart as part of a systemic disease

Question 6

what are the main categories of cardiomyopathies?

Answer 6

o Hypertrophic (HCM)
o Dilated (DCM)
o Restricted (RCM)
o (Also: Arrhythmogenic right ventricular (ARVC) and unclassified CM)

Question 7

what is DCM characterised by?

Answer 7

Characterised by dilation of chambers and decreased systolic function (usually L side)

Right ventricular dilation and dysfunction might be present – not necessary for diagnosis

Question 8

when does DCM occur?

Answer 8

Occurs in the absence of abnormal loading conditions (hypertension, valve disease) or coronary artery disease)

Question 9

what are the causes of DCM?

Answer 9

genetic mutations, infections, inflammation, autoimmune diseases, exposure to toxins and endocrine or neuromuscular causes

Question 10

what are the most common causes of DCM?

Answer 10

Idiopathic and familial disease

Question 11

describe the histopathology in DCM

Answer 11

remodelling of myocardium occurs. Cardiomyocytes are interspersed with necrotic and fibrotic patches and intermittent calcifications

Question 12

what is the pathophysiology of DCM in the early stages?

Answer 12

Myocyte injury –> decreased contractility –> decreased stroke volume –> decreased cardiac output

Question 13

how does the CVS compensate for a reduction in CO in DCM?

Answer 13

o Frank Starling mechanism
o Neurohormonal mechanism; SNS activates increased HR and contractility
o Activation of the renin-angiotensin-aldosterone system

Question 14

what are the detrimental effects of the compensation mechanisms for DCM?

Answer 14

• Increased preload and afterload –> more difficult for the LV to eject blood
• Angiotensin II and aldosterone contribute to pathogenic cardiac remodelling

Question 15

what are the signs and symptoms of DCM and why do they occur?

Answer 15

• Decreased CO – tiredness/fatigue
• Pulmonary oedema – dyspnoea/crackles
• Ascites and peripheral oedema in legs and ankle
• Enlarged heart – leftward displacement of apical beat and possibly 3rd heart sound
• Mitral regurgitation – blood goes back into LA
• Palpitations – caused by arrhythmias

Question 16

what are methods of diagnosing DCM?

Answer 16

signs/symptoms/family history, physical exam, blood tests, ECG, CXR – enlarged heart silhouette, echocardiogram, exercise stress test, cardiac catheterization, CT scan, MRI

Question 17

what are the main treatment methods for DCM?

Answer 17

• medication to control heart failure symptoms
• prevention and treatment of arrhythmias
• cardiac surgery/transplantation

Question 18

what medications can be used to control heart failure symptoms and how do they work?

Answer 18

• Beta blockers – control heart rate
• Anti-coagulants – reduce chance of blood clots forming
• Diuretics – reduce build-up of fluid
• ACE inhibitor/ARBs – lower blood pressure

Question 19

what are the methods to prevent and treat arrhythmias for DCM?

Answer 19

• Medication to control arrhythmias
• Blood thinners to prevent blood clots
• Pacemaker – implanted to control the rhythm of the heart
• Implantable cardioverter defibrillators or ICDs to control the rhythm and chock the heart if it goes out of normal rhythm

Question 20

how are the different types of HCM classified?

Answer 20

depending on location and thickening on different areas of muscle - usually LV, but can be in the septum or RV

Question 21

how is the volume of the ventricle affected in HCM?

Answer 21

volume of ventricle may be normal or reduced

Question 22

what can happen if septal thickening occurs in HCM?

Answer 22

LV outflow tract obstruction or mitral valve dysfunction may be caused

Question 23

how many mutations can cause HCM and what proteins do these affect?

Answer 23

Caused by more than 1400 mutations in at least 13 genes coding for proteins of the sarcomere and Z disc (most commonly affected are myosin-binding protein C and B-myosin heavy chain)

Question 24

what is the inheritance pattern of HCM?

Answer 24

autosomal dominant

Question 25

what are the symptoms of HCM and what causes them?

Answer 25

* Palpitations – caused by arrhythmias. * Chest pain – reduced oxygen levels getting to the heart. * Dizziness or fainting – reduced oxygen levels or blood flow to the brain. * Breathlessness (or dyspnoea) – pulmonary oedema, making it harder to breathe. * Tiredness – reduced cardiac output.

Question 26

how can you diagnose HCM?

Answer 26

* Medical history, physical exam, ECG, exercise ECG, holter monitoring * Echocardiogram – type of ultrasound scan which uses sound waves to make echoes when they hit different body parts. Shows heart structure * MRI scan * Treatment - Medication, devices and surgery

Question 27

what is restrictive cardiomyopathies characterised by? what does this lead to?

Answer 27

Characterised by increased stiffness of the myocardium that causes increased pressure in one or both ventricles • Ventricular relaxation impaired  atria enlarge in response to increased pressure in some patients

Question 28

give examples of restrictive cardiomyopathies

Answer 28

non-infiltrative (idiopathic), infiltrative, storage diseases, endomyocardial diseases

Question 29

what are the causes of RCM?

Answer 29

• Fibrosis or scarring of the endomyocardium • Infiltration of myocardium by an abnormal substance • Genetic and run in the family o Mutations in troponin I recognised as primary mutation in famial RCM

Question 30

what is Loeffler's disease?

Answer 30

infiltration of the heart and lungs by eosinophils in response to a parasitic infection

Question 31

what are signs and symptoms of RCM?

Answer 31

* Decreases CO – fatigue (tiredness) * Systemic congestion * Jugular venous distension * Peripheral oedema * Arrhythmias – palpitations * Possible conduction block * Signs of congestive heart failure may also be present e.g. pulmonary crackles

Question 32

how do you diagnose RCM?

Answer 32

medical history, physical exam, ECG, CXR, CT and MRI

Question 33

what is the prognosis of RCM?

Answer 33

Poor prognosis except when the underlying cause can be treated

Question 34

how is arrhythmogenic RVCM inherited?

Answer 34

autosomal dominant or recessive pattern

Question 35

what do the most common mutations in RCMs affect?

Answer 35

mutation affects cardiac desmosomes  structural and functional alterations – associated with cardiomyocyte apoptosis

Question 36

name a hallmark of ARVC?

Answer 36

Adipose and fibrotic tissue that replace cardiomyocytes are a hallmark of ARVC – primarily in the RV (LV affected later)