Cardiomyopathies with particular reference to the diagnostic relevance of endomyocardial biopsies

A distinction is made between heart muscle diseases with a known cause, or occurring as part of a systemic disease, and those of unknown cause. The first category is termed "specific heart muscle disease". The term "cardiomyopathy" is then limited to the latter category. Cardiomyopathies are categorized as dilated cardiomyopathy, hypertrophic cardiomyopathy and restrictive cardiomyopathy. The pathology of dilated cardiomyopathy depends on the clinical stage of the disease. Basically, the histology shows hypertrophic myocytes, often with degenerative signs, and interstitial fibrosis. Lymphocytes may be observed, particularly in cases studied shortly after the onset of symptoms. Endocardial thickening may occur in time. The role of endomyocardial biopsies in the clinical setting is limited and relates mainly to excluding other diseases, such as myocarditis. The pathology of hypertrophic cardiomyopathy is characterized by myocardial wall thickening, either asymmetric or symmetric, and disorganization of the normal myocardial texture. The latter phenomenon should be distinguished from disarray, since it may occur as a natural phenomenon. The differentiation between these two may be extremely difficult on the basis of only small tissue samples, as with endomyocardial biopsies. This, therefore, poses serious limitations in the use of endomyocardial biopsies. The pathology of restrictive cardiomyopathy also depends on the stage of the disease.(ABSTRACT TRUNCATED AT 250 WORDS)