Page 471 - Textbook of Pathology, 6th Edition

due to mutations causes contractile dysfunction. Another iii) Other contributory factors are: increased circulating level 455
mutation in cytoskeletal protein dystrophin gene on of catecholamines, myocardial ischaemia as a result of
X-chromosome has been held responsible for muscular thickened vasculature of the myocardium and abnormally
dystrophy as well as dilated cardiomyopathy. increased fibrous tissue in the myocardium due to
iv) Chronic alcoholism has been found associated with dilated hypertrophy.
cardiomyopathy. It may be due to thiamine deficiency
induced by alcohol and resulting in beri-beri heart disease MORPHOLOGIC FEATURES. Grossly, the characteristic
(Chapter 9). This is referred to as ‘alcoholic cardiomyopathy’ features are cardiac enlargement, increase in weight,
normal or small ventricular cavities and myocardial
and included by some workers as one of the subtypes of hypertrophy. The hypertrophy of the myocardium is
secondary cardiomyopathy. However, moderate consump- typically asymmetrical and affects the interventricular
tion of alcohol provides some cardioprotection against IHD septum more than the free walls of the ventricles
by raising HDL cholesterol. Another form of alcoholic (Fig. 16.33,B). This asymmetric septal hypertrophy may
cardiomyopathy is associated with consumption of large
quantities of beer (beer drinkers’ myocardiosis). Cobalt added be confined to the apical region of the septum (non-
obstructive type) or may extend up to the level of the mitral
to the beer so as to improve the appearance of foam is thought valve causing obstruction to left ventricular outflow in
to cause direct toxic injury to the heart in this condition. the form of subaortic stenosis (obstructive type). The
v) Peripartum association has been observed in some cases. designation of rhabdomyoma of the septum was applied to
Poorly-nourished women may develop this form of this form of cardiomyopathy in the old literature.
cardiomyopathy within a month before or after delivery Microscopically, the classical feature is the myocardial
(peripartum cardiomyopathy). cell disorganisation in the ventricular septum. The bundles
of myocardial fibres are irregularly and haphazardly
MORPHOLOGIC FEATURES. Grossly, the heart is en- arranged rather than the usual parallel pattern and are
larged and increased in weight (up to 1000 gm). The most separated by bands of interstitial fibrous tissue. The
characteristic feature is prominent dilatation of all the four individual muscle cells show hypertrophy and large
chambers giving the heart typical globular appearance. prominent nuclei.
Thickening of the ventricular walls even if present is CHAPTER 16
masked by the ventricular dilatation (Fig. 16.33,A). The Idiopathic Restrictive (Obliterative or Infiltrative)
endocardium is thickened and mural thrombi are often Cardiomyopathy
found in the ventricles and atria. The cardiac valves are
usually normal. This form of cardiomyopathy is characterised by restriction
Microscopically, The endomyocardial biopsies or autopsy in ventricular filling due to reduction in the volume of the
examination of the heart reveal non-specific and variable ventricles. The common feature in this heterogeneous group
changes. There may be hypertrophy of some myocardial of conditions producing restrictive cardiomyopathy is The Heart
fibres and atrophy of others. Sometimes degenerative abnormal diastolic function. Restrictive cardiomyopathy
changes and small areas of interstitial fibrosis are found includes the following entities:
with focal mononuclear inflammatory cell infiltrate. i) Cardiac amyloidosis
ii) Endocardial fibroelastosis
Idiopathic Hypertrophic Cardiomyopathy iii) Endomyocardial fibrosis
iv) Löeffler’s endocarditis (Fibroplastic parietal endocarditis
This form of cardiomyopathy is known by various synonyms with peripheral blood eosinophilia)
like asymmetrical hypertrophy, hypertrophic subaortic v) Other forms of restrictive cardiomyopathy.
stenosis and Teare’s disease. The disease occurs more
frequently between the age of 25 and 50 years. It is often I) CARDIAC AMYLOIDOSIS. Amyloidosis of the heart
asymptomatic but becomes symptomatic due to heavy may occur in any form of systemic amyloidosis or may occur
physical activity causing dyspnoea, angina, congestive heart as isolated organ amyloidosis in amyloid of aging and result
failure and even sudden death. Though idiopathic, following in subendocardial deposits (Chapter 4).
factors have been implicated: II) ENDOCARDIAL FIBROELASTOSIS. This is an
i) Autosomal dominant inheritance of the disease is available unusual and uncommon form of heart disease occurring
in about half the cases suggesting genetic factors in its predominantly in infants and children under 2 years of age
causation. and less often in adults. The infantile form is clinically
ii) Inherited mutations in genes encoding for sarcomere characterised by sudden breathlessness, cyanosis, cardiac
proteins have been reported in much larger number of cases failure and death whereas the symptoms in the adult form
of hypertrophic cardiomyopathy than those of dilated last for longer duration. The etiology of the condition remains
cardiomyopathy. Particularly implicated are the mutations obscure. However, a number of theories have been proposed.
in heavy and light chains of cardiac β-myosin, troponin-I and These are as under:
troponin-T. The condition may result from myocardial a) The infantile form is believed to be congenital in origin
ischaemia resulting in fibrosis of the intramyocardial arteries occurring due to the effect of intrauterine endocardial anoxia.
and compensatory hypertrophy. The adult form may also be induced by anoxia-causing