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Cardiomyopathies are
diseases characterised by cardiac dysfunction in which the main
abnormality lies in the myocardium. It is expressed as diastolic
and /or systolic ventricular dysfunction. Such abnormalities may
directly affect one or both ventricles in a diffuse or multifocal
fashion and in many patients produce myocardial failure or arrythmias.
Cardiomyopathies have been
traditionally divided into two main categories: (I) Primary
-(idiopathic "heart muscle disease of unknown causes") and (II)
Secondary -("heart muscle diseases of known cause or associated with
disorders of other systems).
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I Primary
cardiomyopathy:
- Dilated
Cardiomyopathy :
Familial ; Idiopathic.
-
Hypertrophic cardiomyopathy :
Obstructive ;
Nonobstructive ; Familial ; Nonfamilial.
-
Restrictive cardiopathy :
Endomyocardial fibrosis ; Idiopathic.
II
Secondary cardiomyopathy:
-Inflammatory ; Metabolic ; Toxic ; Infiltrative ; Physical agents
; Neuromuscular disorders ; Primary tumour of the myocardium ;
Hematologic ; Immunologically mediated cardiomyopathy ;
Miscellaneous. |
Based on
pathophysiology there are three major groups :
1.Dilated
; 2.Hypertrophic ; 3.Restrictive .
Click
on the
 Diagram :
A.
Normal ; B.
Dilated type - Hypertrophy & dilation of left ventricle with normal left
atrium. ; C. Hypertrophic type - Thick left ventricle with small cavity but dilated
left atrium. ; D. Restrictive type -Normal left ventricle but dilated
left atrium.
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Dilated
Cardiomyopathy:
Image Link1;
Image Link2
It
is characterized by slow, progressive hypertrophy and
dilation of four chambers and contractile (systolic) dysfunction.
Age:
This may occur at any age (most common 20-60 years).
Clinical presentation:
Ineffective
ventricular systolic contraction causes congestive heart failure, followed by embolic
complications.
Etiology: The cause is unknown.
May be related to the effect of alcohol toxicity, pregnancy or genetic defect.
Heavy metal ingestion and some cytotoxic drugs give an identitical
picture. Idiopathic cases may be late sequela of viral infection.
Gross:
The heart is enlarged & flabby
.
Poor contractile function and stasis can lead to the formation of
mural thrombi.
-An increase in total heart
weight due to increase in left ventricular (LV) mass ;
-Increase in LV cavity
dimension ;
-Normal or reduced LV wall
thickness ;
-LV endocardial thickening
and mural thrombi in atria or ventricles may or may not be present.
Microscopic
features:
The features include
permutations of the following features:
Image Link
1. Myocyte nuclear
enlargement (polypoidy).
2. Reduction myocyte width
(attenuation)
3. Loss of myofibrils in
myocytes.
4. Diffuse interstitial
fibrosis.
5. Increased numbers of
intertitial lymphocytes.
Hypertrophic
Cardiomyopathy:
Image Link
It is also termed
as idiopathic hypertrophic subaortic and hypertrophic obstructive
cardiomyopathy.
The term hypertrophic
cardiomyopathy is used clinically to denote thick walled left
ventricle (LV) with a small cavity in which systolic contraction is
early and discordinated, leading to outflow obstruction. Diastolic
relaxation is also impaired.
Clinical
presentation:
Most
patients remain stationary and asymptomatic for years, but some
progressively worsen with major complications. Outflow
obstruction is seldom a major problem.
Complications
:
Atrial fibrillation with mural
thrombosis ; Embolization ; Infective
endocarditis ; Congestive heart
failure ;
Sudden death.
Gross:
In hypertrophic cardiomyopathy, the
hypertrophy is not associated with ventricular dilation.
Disproportionate thickness of interventricular septum and free wall of
left ventricle cause bulging of the interventricular septum into left
ventricle forming “banana-like” configuration of left ventricle.
NOTE:
An increase in LV mass with a thick
wall and normal or reduced cavity can occur in 3 separate conditions -
these cannot be separated without histology and knowledge of the
clinical details.
1. Appropriate LV hypertrophy -
there is a defined plausible cause i.e.
aortic valve stenosis or hypertension.
The hypertrophy is
microscopically normal.
2. Inappropriate LV hypertrophy -
there is either no cause or a cause (mild hypertension) insufficient
in degree to responsible for the degree of hypertrophy.
The hypertrophy is
microscopically normal. Examples are renal hypertension,
athletes hearts and the hearts of infants of diabetic mother.
3. Hypertrophic
cardiomyopathy
- In this condition there is a histological abnormality - Myocardial
disarray with bundles running in all directions and interstitial
fibrosis.
Image Link
The condition is
now recognised to be due to 5 different genes (heavy chain
myosin , Tropinin T , myosin binding protein C , tropomyosin and
preexcitation associated gene).
The 4 known genes
are concerned with myofibrillary organisation within the myocyte and
disorganisation leads to misshapen myocytes runnning in whorls. These
genes are dominant negatives in which the mutant protein interferes
with the wild type protein function.
All the genes
carry a risk of sudden unexpected death.
Cases with a
large heavy thick walled LV which may , or may not, be assymmetric are
relatively easy to recognise.Image
Link
About 30% of
cases have a pathognomic subaortic mitral impact lesion.
Pathologists
should be aware that a proportion of cases have normal or mild
increase in LV mass and macroscopically look normal. Microscopy to
identify these cases is needed.
Restrictive
Cardiomyopathy :
In
this form of cardiomyopathy the abnormality of function is in LV
diastolic relaxation. The left atrial pressure rises in an effort to
achieve ventricular filling. This in turn leads to pulmonary
hypertension. The LV remains normal macroscopically, while the right
ventricle hypertrophies. The commonest cause is amyloid.
Primary disease of
the ventricle results in impaired ventricular filling during diastole,
resulting in reduced cardiac outflow. This may be of the
following types:
Endomyocardial fibrosis:
This is typically seen in children and
young adults in Africa. This is characterized by ventricular
subendocardial fibrosis, often with mural thrombus formation.
Reduced ventricular filling is due to
reduced ventricular chamber volume.
Loeffler
endocarditis:
This is
characterized by endo-myocardial fibrosis with large mural thrombi and
is found in temperate zone.
Eosinophilic infiltration is seen in
multiple organs including the heart. There may be associated
peripheral eosinophilia. Cationic proteins released from activated
eosinophils in the circulation damage the endocardium.
These lesions
are rapidly fatal.
Endocardial fibroelastosis:
This uncommon disorder is characterized
by focal-to-diffuse cartilage-like fibroelastic thickening of the
endocardium, mostly of left ventricle. Mostly affected patients are
younger than two years old.
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Problems with Cardiomyopathy:
In some
patients arrythmias and sudden death predominate and contractile
function is normal, the subjects have normal exercise tolerance in
life.
Several
forms exist.
- Arrhythmogenic
right ventricular cardiomyopathy
:
(arrhythmogenic right ventricular dysplasia). This is a familial
disorder, most commonly associated with right-sided heart failure and
various rhythm disturbances, particularly ventricular tachycardia and
sudden death. Morphologically, the dilated right ventricular wall is severely
thinned, with extensive fatty infiltration, loss of myocytes and
interstitial fibrosis. Death occurs due to congestive heart failure,
embolism of mural thrombi or fatal arrhthmias
- In other
subjects there is idiopathic fibrosis in the left ventricle with a
distribution and pattern unlike ischaemic disease. It is not known
whether this is acquired (? post viral) or familial.
- In the
long QT syndrome (often referred to as cardio-myopathy) now known
to be due to genetic defects in sodium and potassium channels in
the myocyte, sudden death is common. The heart is normal
structurally (macro and micro). |
Inflammatory Cardiomyopathy - Myocarditis:
Acute
non-specific
myocarditis usually produces the rapid onset of fever, palpitations
and arrythmia with cardiac failure and a high risk of sudden death.
Pericarditis may or may not be present.
Acute myocarditis is not an
entity recognised by macroscopic examination alone.
Microscopy shows individual
myocyte necrosis and a heavy T lymphocyte infiltrate. Most cases are
due to viral infection with a Coxsackie group predominant. In infants
adenoviruses can cause disproportionate myocyte necrosis with scanty
lymphocytes.
In adults a particularly
florid acute myocarditis is associated with serpigenous areas of
necrosis at the margins of which are numerous macrophage giant cells
and eosinophils. The cause is unknown.
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