Cardiomyopathy refers to disease of the heart muscle in which structural or functional abnormalities affect the myocardium and are not simply explained by conditions such as coronary artery disease, hypertension, valve disease or congenital abnormalities, although definitions and classifications can vary. Cardiomyopathies can impair contraction, relaxation, electrical stability or combinations of these functions. Some are inherited, some arise from acquired causes and some have mixed origins. They can produce heart failure, arrhythmias, thromboembolism or sudden cardiac death, while certain forms remain asymptomatic for long periods and are discovered through family screening or incidental testing.
Major morphological categories include dilated, hypertrophic and restrictive cardiomyopathies, with additional recognised entities such as arrhythmogenic cardiomyopathy and stress-related forms. Dilated cardiomyopathy involves ventricular enlargement and impaired systolic function. Hypertrophic cardiomyopathy involves unexplained myocardial thickening, often most prominent in the ventricular septum, and can impair ventricular filling or obstruct blood leaving the heart. Restrictive cardiomyopathy is characterised primarily by impaired ventricular filling caused by reduced compliance. Arrhythmogenic cardiomyopathy involves structural and electrical abnormalities that can particularly affect ventricular rhythm. These categories describe patterns rather than necessarily identifying a single cause.
Genetics has a major role in several cardiomyopathies. Pathogenic variants affecting proteins involved in the cardiac contractile apparatus, cell junctions, cytoskeleton and other structures can predispose to disease. Inherited cardiomyopathy may follow autosomal dominant, autosomal recessive, X-linked or mitochondrial inheritance depending on the condition and gene involved. Penetrance and expression can vary, meaning that people carrying the same variant may have different degrees of disease. Genetic testing can therefore assist diagnosis and family screening, but a negative genetic test does not necessarily exclude inherited cardiomyopathy because current testing cannot identify every possible genetic cause.
Acquired cardiomyopathies can arise from infections, inflammatory processes, toxins, nutritional deficiencies, endocrine disorders, pregnancy-associated mechanisms and other stresses. Alcohol and certain cancer treatments can contribute to myocardial injury in susceptible individuals. Stress cardiomyopathy, sometimes called Takotsubo syndrome, involves acute and often reversible ventricular dysfunction associated with a characteristic pattern of myocardial stunning and can mimic an acute coronary syndrome. Identifying a potentially reversible cause is clinically important because treatment may differ and cardiac function can improve after the underlying trigger is addressed.
Symptoms depend on the type and severity of disease and can include breathlessness, fatigue, exercise intolerance, chest discomfort, palpitations, dizziness and fainting. Some individuals remain asymptomatic until a serious arrhythmia or acute decompensation occurs. Assessment can include ECG, echocardiography, cardiac magnetic resonance imaging, ambulatory rhythm monitoring, exercise testing, blood tests and genetic investigation. Cardiac MRI can provide detailed information about myocardial structure, tissue characteristics and fibrosis, which can assist diagnosis and risk assessment in selected cardiomyopathies.
Hypertrophic cardiomyopathy is particularly important because it can cause dynamic obstruction of blood leaving the left ventricle, impaired diastolic filling and ventricular arrhythmias. The degree of obstruction can vary with loading conditions and contractility. Management may involve medication to control symptoms and heart rate, specialist treatment for significant obstruction and strategies to reduce sudden-death risk in selected patients. Family assessment can be important because hypertrophic cardiomyopathy frequently has an inherited basis. Exercise recommendations are individualised according to the specific diagnosis, symptoms, arrhythmia risk and specialist assessment rather than applying one universal restriction.
Dilated cardiomyopathy often causes systolic dysfunction and can lead to progressive heart failure. Treatment may use established heart-failure therapies and address underlying causes when identifiable. Arrhythmias are common in several cardiomyopathies and may require medication, ablation or implanted devices. Thrombus formation can occur when ventricular function is severely impaired or particular structural features are present, creating potential embolic complications. Management therefore combines treatment of myocardial dysfunction with assessment of rhythm, thromboembolic risk and the possibility of inherited disease.
Cardiomyopathy is frequently confused with any enlarged or thickened heart, but the term has a more specific clinical meaning and requires consideration of the underlying cause. A hypertrophied heart caused by long-standing hypertension is not automatically classified as hypertrophic cardiomyopathy. Similarly, ventricular dysfunction caused directly by a large myocardial infarction may be described as ischaemic heart disease rather than primary cardiomyopathy. Accurate classification matters because it affects genetic counselling, family screening, treatment, exercise advice and assessment of sudden-death risk. Cardiomyopathy is consequently a diverse group of myocardial diseases rather than one uniform condition.
