- Cardiomyopathy refers to a heterogeneous group of diseases of the heart muscle characterized by structural and functional abnormalities that are not explained solely by coronary artery disease, hypertension, valvular disease, or congenital heart defects. These disorders impair the heart’s ability to pump blood effectively, leading to symptoms of heart failure, arrhythmias, thromboembolic events, and sudden cardiac death. Cardiomyopathies can be inherited or acquired, and their presentation varies widely, ranging from asymptomatic individuals identified incidentally to patients with severe, progressive heart failure requiring advanced interventions such as mechanical support or heart transplantation.
- The condition is broadly classified into several major types based on structural and functional features. Dilated cardiomyopathy (DCM), the most common form, is characterized by dilation of the ventricles and systolic dysfunction, often resulting in progressive heart failure. It can be idiopathic, familial (linked to mutations in genes such as LMNA or TTN), or secondary to factors like viral myocarditis, alcohol, toxins, or chemotherapy. Hypertrophic cardiomyopathy (HCM) is marked by abnormal thickening of the ventricular walls, usually due to genetic mutations affecting sarcomeric proteins. HCM often presents with diastolic dysfunction, outflow tract obstruction, arrhythmias, and increased risk of sudden cardiac death, particularly in young athletes. Restrictive cardiomyopathy (RCM), a rarer type, is characterized by stiff ventricular walls that impair diastolic filling while systolic function remains relatively preserved. Causes include infiltrative diseases such as amyloidosis, sarcoidosis, and hemochromatosis.
- Two additional subtypes have been recognized: arrhythmogenic right ventricular cardiomyopathy (ARVC) and left ventricular noncompaction (LVNC). ARVC is a genetic disorder involving replacement of myocardial tissue with fibro-fatty infiltration, primarily in the right ventricle, leading to arrhythmias and risk of sudden cardiac death. LVNC is thought to arise from arrested myocardial development during embryogenesis, leaving a spongy, trabeculated myocardium that predisposes patients to heart failure, arrhythmias, and thromboembolism.
- The etiology of cardiomyopathy can be genetic, acquired, or mixed. Inherited forms are linked to mutations in genes encoding sarcomeric, cytoskeletal, or desmosomal proteins. Acquired causes include infections (viral myocarditis), toxins (alcohol, chemotherapy drugs such as doxorubicin), endocrine disorders, autoimmune diseases, and nutritional deficiencies. In many cases, especially in DCM, no clear cause can be identified, and the condition is termed idiopathic.
- Clinical manifestations of cardiomyopathy vary depending on the subtype but commonly include dyspnea, fatigue, palpitations, chest pain, syncope, and signs of heart failure such as edema and ascites. Some patients remain asymptomatic until a catastrophic event, such as sudden cardiac death, occurs. Diagnosis typically involves echocardiography to assess ventricular size, wall thickness, and function. Cardiac MRI provides detailed structural and tissue characterization, while ECG, Holter monitoring, and electrophysiological studies help evaluate arrhythmias. Genetic testing is increasingly used to confirm inherited forms and guide family screening.
- Management focuses on symptom relief, prevention of complications, and improving survival. In DCM and HCM, medical therapy includes beta-blockers, ACE inhibitors, ARBs, and diuretics. In HCM, septal reduction therapy (surgical myectomy or alcohol ablation) may be required for obstructive cases. Implantable cardioverter-defibrillators (ICDs) are crucial for preventing sudden cardiac death in high-risk patients. ARVC management often centers on arrhythmia suppression and ICD placement. RCM treatment focuses on addressing the underlying cause (e.g., chelation in hemochromatosis, immunosuppression in sarcoidosis). For advanced disease unresponsive to conventional therapy, ventricular assist devices and heart transplantation remain definitive options.
