A cardiomyopathy is a primary abnormality of the myocardium that usually produces a change in wall thickness, chamber size and mechanical and/or electrical dysfunction.
Cause of cardiomyopathies
Many cases the cause is unknown, however, some genetic abnormalities in cardiac energy metabolism or structural and contractile proteins underlie myocardial dysfunction or are secondary to a systemic or multi-organ disorder.
The classification is based on its clinico-pathologic, aetiology and mechanistic concepts into:
This is the most common cardiomyopathy (90%) characterised by progressive cardiac dilation and contractile (systolic) dysfunction, usually with concomitant hypertrophy.
Dilated cardiomyopathy artiology
Genetic: familial ocurrence in 20-50% of cases, usually but not always autosomal dominant.
Non-genetic: idiopathic, chronic alcoholism, peripartum, myocarditis (coxsackie virus B and other enteroviruses), haemochromatosis, chronic anaemia, doxorubicin,
Macroscopic features of dilated cardiomyopathy
Enlarged heart, 2-3x size of normal, with dilation of all chambers. Wall thinning accompanies dilatation, but wall thickness can be normal if hypertrophy has occurred. Mural thrombi may be seen.
Microscopic features of dilated cardiomyopathy
Clinical features of dilated cardiomyopathy
The idiopathic variety may occur at any age, including childhood but most commonly affects individuals between ages 20-50.
Signs and symptoms of heart failure.
Death is usally attributable to progressive HF over 2-5 years or an arrhythmia or may occur suddenly.
Also called idiopathic hypertrophic subaortic stenosis and hypertrophic obstructive cardiomyopathy.
Causes of hypertrophic cardiomyopathy
Caused by a mutation in one of several genes that encode proteins that are part of the sarcomere - the contractile unit of the cardiac and skeletal muscle that results in myocardial hypertrophy, abnormal diastolic filling (which is reduced) and in about 33% intermittent ventricular outflow obstruction.
Most cases are familial and usually autosomal dominant with variable penetrance. The most common are mutations in the beta-myosin heavy chain, myosin-binding protein C and troponin T and these account for 70-80% of all cases. Why mutations in these genes cause hypertrophy is unknown. Potantially, imapired contraction reuslts in release of growth factors to allow compensatory hypertrophy.
Macroscopic features of hypertrophic cardiomyopathy
Massive myocardial hypertrophy usually without ventricular dilatation.
Classically (90%) of patients there is disproportionate thickening of the ventricular septum as compared with the free wall of the left ventricle 0 termed asymmetrical septal hypertrophy. The left ventricular cavity becomes banana shaped by the bulging of the ventricular septum into the umen. Often subendocardial thickening or mural plaque formation in the left ventricular outflow tract and thickening of teh anteiror mitral valve leaflet,
Microscopic features of Hypertrophic cardiomyopathy
- Extensive myocyte hypertrophy
- Disarray of bundles of myocytes, individual myocytes and myofibres
- Interstitial and replacement fibrosis
The heart is hypercontracting and causes primarily diastolic dysfunction (DD similar features may be seen in amyloidosis and hypertension with age related subaortic septal hypertrophy)
Clinical features of hypertrophic cardiomyopathy
- Reduced chamber size and poor compliance, therefore reduced stroke volume and reduced CO.
- Harsh ejection systolic murmur caused by ventricular outflow obstruction as the anterior mitral valve leaflet moves towards the vetricular septum during systole.
- The high ventricular ischaemia may lead to focal ischaemia
Complications of hypertrophic cardiomyopathy
- Sudden death
- Atrial fibrillation (risk of thrombus)
Characterised by a decrease in ventricular compliance, resulting in impaired ventricular filling during diastole, the contractile function of the left ventricle is usually unaffected.
Aetiology of restrictive cardiomyopathy
May be idiopathic or associated with radiation fibrosis, amyloidosis or sarcoidosis.
Macroscopic features of restrictive cardiomyopathy
Ventricles are of normal size or slightly enlarged. Myocardium is firm. Bi-atrial dilatation is common.
Microscopic feature of restrictive cardiomyopathy
Patchy or diffuse interstitial fibrosis - minimal to extensive.
Rarer cause of restrictive cardiomyopathy.
Unknown aetiology occurring in children and young adults in Africa and other tropical areas.
Rarer cause of restrictive myocarditis.
Endomyocardial fibrosis in association there is often a peripheral eosinophilia - ?myeloproliferative disorder - toxic eosinophil products initiate endocardial damage (necrosis and subsequent fibrosis).
Rarer cause of restrictive cardiomyopathy.
Manifested in the first two years of life, may be associated with a congenital cardiac anomaly, characterised by focal or diffuse fibroelastic thickening usually involving the mural left ventricular endocardium. May be fatal if diffuse involvement.
- Fibrinous and serofibrinous
- Purulent or suppurative pericarditis
Chronic of healed pericarditis may lead to constrictive pericarditis.
Infection, immune mediated: post AMI, rheumatic fever, post surgical
Other: neoplastic cells, renal failure.
Fibrinous and seofibrinous pericarditis
Acute MI, Dressler syndrome, renal failure, rheumatic fever, SLE.
Fibrin deposition, granular roughening, may lead to organisation and constrictive pericarditis.
Dressler's syndrome is a secondary form of pericarditis that occurs in the setting of injury to the heart or the pericardium (the outer lining of the heart). It consists of a triad of features: fever, pleuritic pain and pericardial effusion.
Purulent or suppurative pericarditis
Direct extension from neighbouring infections, seeding from the blood, lymphatic extension, introduction through crditomy. Heart coated with an inflammatory exudate and effusion.
Blood mixed with fibrinous or purulent effusion - malignant neoplasm spread to pericardial sac is commonest cause.
Tuebrculosis most likely.