Hypertrophic and dilated cardiomyopathies
The etiology of non-familial cardiomyopathies largely determines patient management tactics. The American Heart Association identifies specific triggers for each phenotype.
Hypertrophic cardiomyopathy (HCM) is characterized by thickening of the ventricular walls. Its non-familial causes include:
- Presence of obesity.
- Being born to a mother suffering from diabetes mellitus.
- Various fatty acid metabolism disorders.
- Intensive sports training (formation of the so-called "athlete's heart").
- Deposition of amyloid in tissues (amyloidosis).
Dilated cardiomyopathy (DCM) manifests as enlargement of the heart chambers. This condition has the widest spectrum of causes:
- Previous myocarditis and persistence of viral infections.
- Systemic pathologies such as Kawasaki disease and eosinophilic lesions.
- Toxic effects of medications and alcohol.
- Conditions associated with pregnancy, endocrine disorders, and nutritional disturbances.
- Chronic rhythm disturbances (tachycardiomyopathy).
Arrhythmogenic, restrictive, and unclassified forms
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is not yet fully understood in the context of non-familial factors. An inflammatory process is considered the putative mechanism for the development of this pathology.
Restrictive cardiomyopathy (RCM) is accompanied by decreased elasticity of the heart walls, which impairs its diastolic relaxation. Key etiological factors include:
- Amyloidosis and scleroderma.
- Endomyocardial fibrosis.
- Oncological processes: carcinoid heart disease and metastatic myocardial lesions.
- Radiation exposure (including the consequences of radiation therapy).
- Use of specific medications.
Separately mentioned in the classification are unclassified forms, a prominent representative of which is Takotsubo cardiomyopathy.
Echocardiographic pattern of HCM
Diagnostic imaging, particularly echocardiography (EchoCG), plays a decisive role in verifying cardiomyopathies. In the hypertrophic form, pronounced myocardial thickening is visualized.
M-mode evaluation (M-mode) This mode allows precise linear measurements of structures over time. In severe HCM, the following parameters may be observed:
- Left ventricular end-diastolic dimension (LVEDD) is about 44 mm.
- Left ventricular end-systolic dimension (LVESD) is 28 mm.
- Interventricular septum (IVS) thickness reaches 28 mm. Such pathological thickening is a reliable sign of HCM.
B-mode evaluation (B-mode) When examining in the short-axis view (short-axis images), the diastolic and systolic phases are analyzed. The echocardiogram visualizes clear signs of a sharply hypertrophied interventricular septum, which complements the data from the one-dimensional mode and forms a complete clinical picture of the pathology.
Briefly: answers to topical questions
What echocardiographic signs are characteristic of dilated cardiomyopathy?
The main echocardiographic sign of dilated cardiomyopathy is pronounced enlargement (dilatation) of the left ventricle.
Which genetic mutations cause the familial form of hypertrophic cardiomyopathy?
The familial form of hypertrophic cardiomyopathy is caused by various genetic mutations, most of which are unique.
- Sarcomeric protein mutations — the most common cause (11 mutations identified, with β-myosin heavy chain mutation predominating).
- Multiple mutations — combinations of two or more pathogenic variants, most commonly in sarcomeric protein genes.
- Non-sarcomeric gene mutations — account for 15–20% of causes (pathogenic variants in genes for cytoskeleton proteins, ion channels, Z-discs).
Glycogen storage diseases and lysosomal storage disorders are also classified as familial forms.
What MRI signs are characteristic of arrhythmogenic right ventricular cardiomyopathy?
A characteristic MRI sign of arrhythmogenic right ventricular cardiomyopathy is the presence of myocardial fatty infiltration.
- Fatty infiltration — detected in the "triangle of dysplasia" (subtricuspid region, apex, free wall of the outflow tract).
- Right ventricular enlargement — assessed using quantitative parameters, as is the ejection fraction.
The method has limitations: due to spatial resolution, fat can only be detected with extensive myocardial replacement, making it difficult to differentiate intramyocardial fat from subepicardial fat.
To remember the main groups of cardiomyopathies, use the phrase: "Proud Dolphin Rejoices at Shark" (Hypertrophic, Dilated, Restrictive, Arrhythmogenic).
Class and exam questions
Non-familial causes of HCM include obesity, fatty acid metabolism disorders, amyloidosis, and the development of pathology in children whose mothers have diabetes mellitus.
Non-familial causes of HCM include obesity, fatty acid metabolism disorders, amyloidosis, and the development of pathology in children whose mothers have diabetes mellitus.
Radiation exposure, metastatic tumors, and carcinoid heart disease are classic causes of restrictive cardiomyopathy (RCM).
Radiation exposure, metastatic tumors, and carcinoid heart disease are classic causes of restrictive cardiomyopathy (RCM).
This parameter, detected in M-mode, indicates pathological thickening of the interventricular septum and is a confirmatory criterion for hypertrophic cardiomyopathy.
This parameter, detected in M-mode, indicates pathological thickening of the interventricular septum and is a confirmatory criterion for hypertrophic cardiomyopathy.
What else to study on this topic
- Pathogenesis of Takotsubo cardiomyopathy as an unclassified form
- Differential diagnosis of "athlete's heart" versus pathological HCM
- The role of inflammation in the development of arrhythmogenic right ventricular cardiomyopathy
- The impact of persistent viral infections on the development of DCM
- Assessment of LV systolic and diastolic functions in B-mode in cardiomyopathies
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