Cardiomyopathies Flashcards
What is the pathophysiology of hypertrophic obstructive cardiomyopathy?
the most common defects involve a mutation in the gene encoding β-myosin heavy chain protein or myosin-binding protein C
results in predominantly diastolic dysfunction
left ventricle hypertrophy → decreased compliance → decreased cardiac output
characterized by myofibrillar hypertrophy with chaotic and disorganized fashion myocytes (‘disarray’) and fibrosis on biopsy
Symptoms of hypertrophic obstructive cardiomyopathy?
often asymptomatic
exertional dyspnoea
angina
syncope
typically following exercise
due to subaortic hypertrophy of the ventricular septum, resulting in functional aortic stenosis
sudden death (most commonly due to ventricular arrhythmias), arrhythmias, heart failure
jerky pulse, large ‘a’ waves, double apex beat
systolic murmurs
ejection systolic murmur: due to left ventricular outflow tract obstruction. Increases with Valsalva manoeuvre and decreases on squatting
pansystolic murmur: due to systolic anterior motion of the mitral valve → mitral regurgitation
What is found on echo and ECG of hypertrophic obstructive cardiomyopathy?
Echo-mnemonic - MR SAM ASH
mitral regurgitation (MR)
systolic anterior motion (SAM) of the anterior mitral valve leaflet
asymmetric hypertrophy (ASH)
ECG
left ventricular hypertrophy
non-specific ST segment and T-wave abnormalities, progressive T wave inversion may be seen
deep Q waves
atrial fibrillation may occasionally be seen
What is the pathophysiology of Arrhythmogenic right ventricular cardiomyopathy ?
inherited in an autosomal dominant pattern with variable expression
the right ventricular myocardium is replaced by fatty and fibrofatty tissue
around 50% of patients have a mutation of one of the several genes which encode components of desmosome
How does Arrhythmogenic right ventricular cardiomyopathy present?
palpitations
syncope
sudden cardiac death
How do we investigate Arrhythmogenic right ventricular cardiomyopathy ?
ECG abnormalities in V1-3, typically T wave inversion. An epsilon wave is found in about 50% of those with ARV - this is best described as a terminal notch in the QRS complex
echo changes are often subtle in the early stages but may show an enlarged, hypokinetic right ventricle with a thin free wall
magnetic resonance imaging is useful to show fibrofatty tissue
How do we manage Arrhythmogenic right ventricular cardiomyopathy?
drugs: sotalol is the most widely used antiarrhythmic
catheter ablation to prevent ventricular tachycardia
implantable cardioverter-defibrillator
Pathophysiology of DCM
A huge number of conditions can cause DCM. This includes infections (e.g. parvovirus B19, coxsackievirus), drugs (e.g. Doxorubicin), pregnancy (e.g. Peripartum) and inherited causes (e.g. abnormal sarcomere genes) amongst many others.
In DCM, there is progressive dilatation of the left ventricular cavity
Symptoms of DCM?
Breathlessness
Reduced exercise tolerance
Fatigue
Orthopnoa
Paroxsymal nocturnal dyspnoea: severe, sudden shortness of breath, usually at nighttime
Peripheral oedema
Palpitations: due to the development of arrhythmias
How do we diagnose DCM?
A diagnosis of dilated cardiomyopathy requires evidence of dilation and impaired contraction of the left ventricle or both ventricles, which can be visualised on echocardiography.
How do we manage DCM?
Treatment of DCM essentially mirrors that of chronic heart failure. This involves the use of both prognostic medications (e.g. angiotensin receptor antagonists, beta-blockers) and medications to improve symptoms (e.g. diuretics). For more information see our notes on Heart failure.
What is the pathophysiology of RCM?
RCM is much less common than the other cardiomyopathies. It is commonly the result of infiltrative diseases where there is a deposition of substance in the myocardium such as amyloid, iron or granulomas. As such, classic causes include amyloidosis, haemochromatosis (iron overload) and sarcoidosis. It can also occur due to inheritance of an abnormal sarcomere gene, storage diseases or tropical diseases (e.g. endomyocardial fibrosis).
Infiltration of the heart reduces compliance and this leads to inadequate ventricular filling in diastole. This causes increased pressures, dilated atria and the development of diastolic heart failure.
Symptoms of RCM?
breathlessness, fatigue, peripheral oedema, paroxysmal nocturnal dyspnea, reduced exercise tolerance and/or palpitations. Patients may develop syncope due to conduction disease, especially with infiltrative diseases that may damage the sinoatrial node or atrioventricular node.
How do we diagnose RCM?
Formal imaging such as echocardiography or cardiac MRI. This shows evidence of non-dilated, non-thickened ventricles with abnormal ventricular filling, features of diastolic dysfunction and usually atrial enlargement. However, it can be difficult to identify diastolic dysfunction.
How to we manage RCM?
Treatment of RCM should be aimed at the underlying cause whilst optimising patients with heart failure, particularly fluid overload. However, many prognostic medications used in chronic heart failure are ineffective in patients with RCM.
