cardiomyopathies Flashcards
what is the myocardium?
thickest layer of the heart. Composed of cardiac muscle§
what is the functional unit of the myocardium?
sarcomere
what is a cardiomyopathy?
any disease of the myocardium that can’t be explained by coronary artery narrowing or abnormal loading of ventricles
what are primary cardiomyopathies?
genetic, mixed (genetic and nonmixed) or non-genetic (acquired) causes and are confined solely to the heart
what are secondary cardiomyopathies?
affect the heart as part of a systemic disease
what are the main categories of cardiomyopathies?
o Hypertrophic (HCM) o Dilated (DCM) o Restricted (RCM) o (Also: Arrhythmogenic right ventricular (ARVC) and unclassified CM)
what is DCM characterised by?
Characterised by dilation of chambers and decreased systolic function (usually L side)
Right ventricular dilation and dysfunction might be present – not necessary for diagnosis
when does DCM occur?
Occurs in the absence of abnormal loading conditions (hypertension, valve disease) or coronary artery disease)
what are the causes of DCM?
genetic mutations, infections, inflammation, autoimmune diseases, exposure to toxins and endocrine or neuromuscular causes
what are the most common causes of DCM?
Idiopathic and familial disease
describe the histopathology in DCM
remodelling of myocardium occurs. Cardiomyocytes are interspersed with necrotic and fibrotic patches and intermittent calcifications
what is the pathophysiology of DCM in the early stages?
Myocyte injury –> decreased contractility –> decreased stroke volume –> decreased cardiac output
how does the CVS compensate for a reduction in CO in DCM?
o Frank Starling mechanism
o Neurohormonal mechanism; SNS activates increased HR and contractility
o Activation of the renin-angiotensin-aldosterone system
what are the detrimental effects of the compensation mechanisms for DCM?
- Increased preload and afterload –> more difficult for the LV to eject blood
- Angiotensin II and aldosterone contribute to pathogenic cardiac remodelling
what are the signs and symptoms of DCM and why do they occur?
- 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
what are methods of diagnosing DCM?
signs/symptoms/family history, physical exam, blood tests, ECG, CXR – enlarged heart silhouette, echocardiogram, exercise stress test, cardiac catheterization, CT scan, MRI
what are the main treatment methods for DCM?
- medication to control heart failure symptoms
- prevention and treatment of arrhythmias
- cardiac surgery/transplantation
what medications can be used to control heart failure symptoms and how do they work?
- 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
what are the methods to prevent and treat arrhythmias for DCM?
- 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
how are the different types of HCM classified?
depending on location and thickening on different areas of muscle - usually LV, but can be in the septum or RV
how is the volume of the ventricle affected in HCM?
volume of ventricle may be normal or reduced
what can happen if septal thickening occurs in HCM?
LV outflow tract obstruction or mitral valve dysfunction may be caused
how many mutations can cause HCM and what proteins do these affect?
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)
what is the inheritance pattern of HCM?
autosomal dominant
what are the symptoms of HCM and what causes them?
- 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.
how can you diagnose HCM?
- 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
what is restrictive cardiomyopathies characterised by? what does this lead to?
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
give examples of restrictive cardiomyopathies
non-infiltrative (idiopathic), infiltrative, storage diseases, endomyocardial diseases
what are the causes of RCM?
• 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
what is Loeffler’s disease?
infiltration of the heart and lungs by eosinophils in response to a parasitic infection
what are signs and symptoms of RCM?
- 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
how do you diagnose RCM?
medical history, physical exam, ECG, CXR, CT and MRI
what is the prognosis of RCM?
Poor prognosis except when the underlying cause can be treated
how is arrhythmogenic RVCM inherited?
autosomal dominant or recessive pattern
what do the most common mutations in RCMs affect?
mutation affects cardiac desmosomes structural and functional alterations – associated with cardiomyocyte apoptosis
name a hallmark of ARVC?
Adipose and fibrotic tissue that replace cardiomyocytes are a hallmark of ARVC – primarily in the RV (LV affected later)