2.02 - Cardiomyopathies Flashcards
What is cardiomegaly?
Increase in cardiac weight or size
What is hypertrophy?
thickened heart muscle due to increased cell size
What is cardiac dilation?
Increase in size of heart chambers
Describe the structure of cardiac muscle
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)
Describe intercalated discs
Specialised cellular junctions
Permit rapid spread of contractile stimuli due to areas of low electoral resistance. Necessary for simultaneous contraction of all fibres
Describe the sarcoplasmic reticulum
Calcium storage. Slow calcium leak from SR and T tubules –> automatic contractions
Describe the sarcomere
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
What is cardiomyopathy?
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
What are some of the common presentations of cardiomyopathy?
Syncope Heart failure Sudden Death Thromboembolism Chest pain Arrhythmias Fatigue Shortness of breath
How can cardiomyopathies be classified?
Cause (Primary, secondary, idiopathic)
Macroscopic (pathologic) appearance (most common method)
Genetic mutation / inheritance
Functional (diastolic failure, systolic failure)
What are the functional consequences of diastolic heart failure?
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
What are the functional consequences of systolic heart failure?
Decreased cardiac output
Often associated with dilated chambers.
Heart is not able to contract properly and get that SV out
What are the four main primary cardiomyopathies?
Dilated Cardiomyopathy (DCM) Hyperthrophic Cardiomyopathy (HCM) Restrictive Cardiomyopathy (RCM) Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)
What are some secondary causes of cardiomyopathies?
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)
What are the primary causes of cardiomyopathies?
Genetic mutations causing defects in cytoskeleton, contractile protiens or mitochondrial oxidative phosphorylation can lead to cardiomyopathies
Frequently inherited in an autosomal dominant fashion
Describe Dilated Cardiomyopathy (DCM)
90% of all cardiomyopathies
Progressive cardiac dilatation with or without hypertrophy (4-chamber)
Systolic dysfunction
Presentation with congestive heart failure/ arrhythmia
What are the main causes of DCM?
Alcohol Pregnancy (can sometimes be reversible) Infections Genetic (likely due to mutations in genes for cytoskeletal proteins Idiopathic
Describe the macroscopic appearance of DCM
Large, globular, flabby, heavy heart with dilated chambers (especially ventricles)
Ventricle wall thickness normal or increased
What are some complication of DCM
Mural thrombi – embolism Myocardial ischaemia Ventricular arrhythmias Congestive heart failure Functional valvular dysfunction / incompetence
Describe Hypertrophic/Obstructive Cardiomyopathy (HOCM)
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
Describe the genetics of HOCM
Virtually all are inherited
Autosomal dominant resulting from mutations coding sarcomeric proteins
Most common is beta myosin heavy chain
Describe the macroscopic appearance of HOCM
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
Describe the histological appearance of HOCM
Extreme myocyte hypertrophy and myocyte disarray
Individual myocytes whorled, tangled and pinwheel configuration
Disarray of contractile elements within cells
Interstitial fibrosis
List some complications of HOCM
Arrhythmias: atrial fibrillation, ventricular arrhythmias
Symptoms: syncope/dizziness (especially during exercise)
Mural thrombi
Myocardial ischaemia
Sudden death
Describe Restrictive Cardiomyopathy (RCM)
Least common
Stiff ventricles causing increased intraventricular pressure and impaired ventricular filling during diastole
Important to differentiate from constrictive pericarditis
What are some causes of RCM
Idiopathic
Genetic (sarcomeric proteins)
Associated with infiltrative myocardial diseases (amyloidosis, haemochromatosis, sarcoidosis)
Endomyocardial diseases (thickening of the endocardial layer causing stiffening)
Describe the histology os RCM
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
Describe Arrhythmogenic Right Ventricular Cardiomopathy (ARVC)
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
