Cardiomyopathy

Causes

Cardiomyopathies can be of genetic (familial) or non-genetic (acquired) origin. Genetic cardiomyopathies usually are caused by sarcomere or cytoskeletal diseases, neuromuscular disorders, inborn errors of metabolism, malformation syndromes and sometimes are unidentified. Non-genetic cardiomyopathies can have definitive causes such as viral infections, myocarditis and others.

Cardiomyopathies are either confined to the heart or are part of a generalized systemic disorder, both often leading to cardiovascular death or progressive heart failure-related disability. Other diseases that cause heart muscle dysfunction are excluded, such as coronary artery disease, hypertension, or abnormalities of the heart valves. Often, the underlying cause remains unknown, but in many cases the cause may be identifiable. Alcoholism, for example, has been identified as a cause of dilated cardiomyopathy, as has drug toxicity, and certain infections (including Hepatitis C). Untreated celiac disease can cause cardiomyopathies, which can completely reverse with a timely diagnosis. In addition to acquired causes, molecular biology and genetics have given rise to the recognition of various genetic causes.

A more clinical categorization of cardiomyopathy as 'hypertrophied', 'dilated', or 'restrictive', has become difficult to maintain because some of the conditions could fulfill more than one of those three categories at any particular stage of their development.The current American Heart Association (AHA) definition divides cardiomyopathies into primary, which affect the heart alone, and secondary, which are the result of illness affecting other parts of the body. These categories are further broken down into subgroups which incorporate new genetic and molecular biology knowledge.

Mechanism

The pathophysiology of cardiomyopathies is better understood at the cellular level with advances in molecular techniques. Mutant proteins can disturb cardiac function in the contractile apparatus (or mechanosensitive complexes). Cardiomyocyte alterations and their persistent responses at the cellular level cause changes that are correlated with sudden cardiac death and other cardiac problems.

Cardiomyopathies are generally varied individually. Different factors can cause cardiomyopathies in adults as well as children. For example, dilated cardiomyopathy in adults is associated with ischemic cardiomyopathy, hypertension, valvular diseases, and genetics. In children, neuromuscular diseases such as Becker muscular dystrophy or X-linked genetic disorder, are directly linked with cardiomyopathies.

Diagnosis

Among the diagnostic procedures done to determine a cardiomyopathy are:

• Physical exam
• Family history
• Blood test
• ECG
• Echocardiogram
• Stress test
• Genetic testing

Classification

Cardiomyopathies can be classified using different criteria:

• Primary/intrinsic cardiomyopathies
  • Congenital
    • Hypertrophic cardiomyopathy (HCM)
    • Arrhythmogenic right ventricular cardiomyopathy (ARVC)
    • Left ventricular noncompaction
    • Ion Channelopathies like the Long QT syndrome and the very rare Short QT syndrome
    • Catecholaminergic polymorphic ventricular tachycardia
  • Mixed
    • Dilated cardiomyopathy (DCM)
    • Restrictive cardiomyopathy (RCM)
    • Brugada syndrome
  • Acquired
    • Stress cardiomyopathy
    • Myocarditis, inflammation of and injury to heart tissue due in part to its infiltration by lymphocytes and monocytes
    • Eosinophilic myocarditis, inflammation of and injury to heart tissue due in part to its infiltration by eosinophils
    • Ischemic cardiomyopathy (not formally included in the classification, due to ischemic cardiomyopathy being a direct result of another cardiac problem)
• Secondary/extrinsic cardiomyopathies
  • Metabolic/storage
    • Fabry's disease
    • Hemochromatosis
  • Endomyocardial
    • Endomyocardial fibrosis
    • Hypereosinophilic syndrome
  • Endocrine
    • Diabetes mellitus
    • Hyperthyroidism
    • Acromegaly
  • Cardiofacial
    • Noonan syndrome
  • Neuromuscular
    • Muscular dystrophy
    • Friedreich's ataxia
  • Other
    • Obesity-associated cardiomyopathy

Treatment

Treatment may include suggestion of lifestyle changes to better manage the condition. Treatment depends on the type of cardiomyopathy and condition of disease, but may include medication (conservative treatment) or iatrogenic/implanted pacemakers for slow heart rates, defibrillators for those prone to fatal heart rhythms, ventricular assist devices (VADs) for severe heart failure, or catheter ablation for recurring dysrhythmias that cannot be eliminated by medication or mechanical cardioversion. The goal of treatment is often symptom relief, and some patients may eventually require a heart transplant.Acoramidis (Attruby) was approved for medical use in the United States in November 2024, to treat adults with cardiomyopathy of wild-type or variant (hereditary) transthyretin-mediated amyloidosis (ATTR-CM) to reduce death and hospitalization related to heart problems.