diseases primarily affecting heart muscle Once cases of ischaemic heart disease,
valvular heart disease,
and hypertensive heart disease have been excluded, there remains a group of
patients who have presented with abnormal cardiac
function due to primary disease of the myocardium.
These disorders, termed
cardiomyopathies, can be considered together, as the diseases have a primary
impact on cardiac muscle
Many have a defined cause and can be classed as secondary cardiomyopathies.
Other diseases have, as yet,
no defined cause and are classed as idiopathic primary cardiomyopathies.
The cardiomyopathies usually
cause progressive development of cardiac failure.
The time scale varies
according to the cause of
disease; development may occur over weeks or years.
In some instances, sudden
cardiac death is the first manifestation of disease.
Diseases that infiltrate the
myocardium causing abnormal rigidity are termed restrictive cardiomyopathies,
Primary cardiomyopathies are
classified according to myocardial dysfunction
follow two main patterns according to the dysfunction of the myocardium.
cardiomyopathy the heart walls (especially the left ventricle) are enormously
thickened and hypertrophied, often
in an asymmetrical pattern, particularly affecting the interventricular septum.
Catheter studies show an abnormal pressure
gradient along the left ventricular cavity. Histologically there is disorganized
branching of hypertrophied muscle fibres, which show
loss of the normal parallel orientation.
In about 50% of cases, hypertrophic
cardiomyopathy is inherited as an autosomal dominant
disorder; it occurs most often in young adults and juveniles, and may present
with sudden, unexplained death on exertion.
Less dramatic presentations include
angina and breathlessness on exertion in a young person, or repeated fainting
In some kindreds this is due to a point mutation in the gene coding for
In hypertrophic cardiomyopathy there is
marked left ventricular hypertrophy. This often preferentially affects the
Dilated (congestive) cardiomyopathy
the ventricles are dilated, the chamber walls
stretched thin, and the muscle is poorly
Typically, there is an elevated ventricular end-diastolic
The cause is not known, but
some cases may follow viral myocarditis.
Myocarditis is a rare
disease in which diffuse inflammation of the myocardium occurs
Inflammation of the
myocardium, termed myocarditis, is generally rare.
Although it is considered by
many to be grouped best as a
cardiomyopathy, others categorize this pattern of disease separately.
The myocardium shows interstitial oedema and infiltrate with lymphocytes and
The disease can be caused by
direct infection, e.g.Trypanosoma cruzi (Chagas' disease), Coxsackie A and B
viruses, HIV, influenza,
Epstein-Barr virus, and fungi; toxin-mediated damage, e.g. diphtheria, typhoid
and septicaemic states; and immune hypersensitivity,
e.g. acute rheumatic fever.
There are also idiopathic causes, such as giant-cell myocarditis.