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Cardiomyopathy: a necessary revision of the WHO classification
Insights
The 1980 WHO/ISFC classification distinguishes cardiomyopathies. Two new forms, primary restrictive cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy, are recognized as distinct heart muscle diseases of unknown origin.
Area of Science:
- Cardiology
- Pathology
- Genetics
Background:
- The World Health Organization/International Society and Federation of Cardiology (WHO/ISFC) task force established a classification for myocardial diseases in 1980.
- This classification differentiates specific heart muscle diseases from cardiomyopathies, which are myocardial diseases of unknown origin.
- Cardiomyopathies were categorized into dilated, hypertrophic, and restrictive forms, with endomyocardiofibrosis and fibroblastic parietal endocarditis included in the restrictive group.
Purpose of the Study:
- To introduce and describe two newly recognized forms of heart muscle disease: primary restrictive cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy.
- To emphasize the distinct characteristics and classification of these novel conditions.
- To advocate for their classification as heart muscle diseases of unknown origin, separate from existing WHO categories.
Main Methods:
- Review and analysis of existing literature and diagnostic criteria for heart muscle diseases.
- Comparative analysis of anatomical, functional, clinical, and histological features of primary restrictive cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy.
- Evaluation against the established WHO/ISFC classification framework.
Main Results:
- Primary restrictive cardiomyopathy presents with normally sized, non-hypertrophic ventricles, dilated atria, impaired diastolic compliance due to myocardial stiffness, and chronic congestive heart failure.
- Histological findings in primary restrictive cardiomyopathy include interstitial fibrosis and myocardial disarray, without hypereosinophilia.
- Arrhythmogenic right ventricular cardiomyopathy is characterized by the substitution of right ventricular free wall myocardium with fibrous or adipose tissue, leading to regional dynamic alterations and ventricular arrhythmias, with the left ventricle typically unaffected.
Conclusions:
- Primary restrictive cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy represent distinct entities within heart muscle diseases.
- These two conditions should be classified as heart muscle diseases of unknown origin.
- It is crucial to maintain a clear distinction between these newly recognized forms and other cardiomyopathies previously listed in the WHO classification.
Abstract:
The classification of myocardial disease proposed by the WHO/ISFC task force in 1980 distinguishes specific heart muscle diseases from myocardial diseases of unknown origin, termed cardiomyopathies, and differentiated into the dilated, hypertrophic and restrictive forms. This last group includes endomyocardiofibrosis and fibroblastic parietal endocarditis. In more recent years, two new forms of heart muscle disease have been recognized: so-called "primary" restrictive cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy. Primary restrictive cardiomyopathy is characterized anatomically by normally sized, non-hypertrophic ventricles with dilated atria, and functionally by impaired diastolic compliance due to myocardial stiffness. The clinical picture is that of chronic congestive heart failure; histology shows interstitial fibrosis and myocardial disarray, but not hypereosinophilia. In arrhythmogenic right ventricular cardiomyopathy, the myocardium of the right ventricular free wall is substituted by fibrous and/or adipose tissue, which results in regional dynamic alterations and ominous ventricular arrhythmias. The left ventricle is usually spared. Both forms should be classified as heart muscle diseases of unknown origin, and kept clearly distinct from the other cardiomyopathies listed in the WHO classification.