Cardiomyopathy

Key points

• Most cases of dilated cardiomyopathy present as congestive heart failure, and, thus, the same treatment is used for both conditions
• The presentation of hypertropic cardiomyopathies is quite variable and may include dyspnea, chest pain, syncope or presyncope, abnormal electrocardiographic findings, or abnormal cardiac examination findings
• Treatment of hypertrophic cardiomyopathy can be problematic and usually requires the help of a specialist
• Immediate action is required in the following:
  • Patients with cardiomyopathy and hypotension to prevent irreversible cardiogenic shock
  • Patients with dilated cardiomyopathy and hypothermia, which is a sign of a severe reduction in cardiac output
• Fluid retention should be addressed as a cause of worsening shortness of breath
• Respiratory failure or cardiac arrest is a medical emergency
• Prompt evaluation is necessary in patients with a history of syncope

Background

Description

• Cardiomyopathy is a disease of the heart muscle that results in abnormal cardiac function
• Dilated cardiomyopathy is characterized by enlargement of the heart cavity and systolic dysfunction of one or both ventricles in the absence of congenital, coronary, hypertensive, valvular, or pericardial heart disease
• Hypertrophic cardiomyopathy is characterized by left ventricular hypertrophy without an identifiable cause that results in impaired diastolic filling
• Restrictive cardiomyopathy is characterized by restricted filling and reduced diastolic volume of either or both ventricles, with normal or nearly normal wall thickness and systolic function; the condition is relatively uncommon, can occur in young patients, and tends to be progressive

Epidemiology

Incidence and prevalence

• The incidence of dilated cardiomyopathy is 148 cases per 100,000 persons per year
• The estimated prevalence of dilated cardiomyopathy is 920 cases per 100,000 persons and that of hypertrophic cardiomyopathy is 50 to 200 cases per 100,000 persons
• Restrictive cardiomyopathy is the most rarely encountered form of heart muscle disease in Western countries

Demographics

Age:

• The incidence of ischemic cardiomyopathy, which is due to coronary artery disease, is higher in elderly patients
• Nonischemic cardiomyopathies can occur at any age, including during childhood, and, thus, should be suspected in young patients presenting with a cardiomyopathy of unknown etiology because the likelihood of coronary artery disease is low
• Hypertrophic cardiomyopathy most commonly presents in the third decade of life, although it may occur throughout the lifespan. Among children, the condition is most likely to present in the second decade of life
• The risk of sudden death due to hypertrophic cardiomyopathy is greatest in patients under age 30
• Arrhythmias secondary to arrhythmogenic right ventricular dysplasia usually present in adolescence or early adulthood

Gender:

• Dilated cardiomyopathy occurs more frequently in male patients than in female patients (approximately 3:1)
• Hypertrophic cardiomyopathy is slightly more prevalent among male patients, although its inheritance is not sex linked. Female patients with the disease tend to present at an earlier age than male patients
• Arrhythmogenic right ventricular dysplasia has a male predominance

Race:

• Dilated cardiomyopathy occurs more frequently in black patients than in white patients (approximately 2.5:1).

Genetics:

• Hypertrophic cardiomyopathy is generally inherited as an autosomal dominant trait with variable penetrance and expressivity. Echocardiography shows disease in approximately one fourth of first-degree relatives of patients with this condition
• Different genetic mutations are associated with different prognoses. Patients with troponin T mutations are at increased risk for sudden death, which can occur without evidence of significant left ventricular hypertrophy
• A minority of patients have a sporadic, nonfamilial form of the disease
• Up to 30% of instances of otherwise idiopathic dilated cardiomyopathy suggest familial inheritance
• Familial inheritance is not characteristic of restrictive cardiomyopathy
• Arrhythmogenic right ventricular dysplasia is a genetic disorder that can be sporadic, but both autosomal dominant and recessive inheritance have been described

Geography:

• Restrictive cardiomyopathy is more prevalent in tropical Africa than in the Western world

Causes and risk factors

Causes

Common:

• Dilated cardiomyopathy:
  • Ischemic
  • Idiopathic
  • Genetic: a pattern of familial inheritance is evident in up to 20% of cases of otherwise idiopathic dilated cardiomyopathy
  • Alcoholism
  • Tachycardia-induced dilated cardiomyopathy is seen in patients with prolonged tachycardia (either sinus rhythm or a supraventricular tachycardia) and is most commonly caused by atrial fibrillation and atrial flutter with rapid ventricular response
  • Abuse of illegal drugs, including cocaine, methamphetamine, and heroin
  • Prescription medications, including certain chemotherapeutic agents (anthracyclines, mitoxantrone, cyclophosphamide, trastuzumab, sunitinib, lapatinib) and phenothiazines
  • Pregnancy, particularly during the peripartum period in women with preeclampsia or multiple births
  • Hemochromatosis
  • Human immunodeficiency virus (HIV) disease and exposure to antiretroviral agents used to treat acquired immunodeficiency syndrome (AIDS)
  • Infectious disease (coxsackievirus, adenovirus, cytomegalovirus, Rocky Mountain spotted fever, Q fever, toxoplasmosis, trichinosis, leptospirosis, Lyme disease, Chagas disease)
• Hypertrophic cardiomyopathy:
  • Most cases have a genetic origin, caused by a number of possible genotypic abnormalities
  • A variant form of the gene encoding the β-cardiac myosin heavy chain is the most commonly identified cause
  • Certain mutations may be associated with an increased risk of sudden death
• Restrictive cardiomyopathy:
  • Infiltrative and storage disorders, most typically amyloidosis but also glycogen storage disease, sarcoidosis, hemochromatosis, and eosinophilic endomyocardial disease
  • Idiopathic

Rare:

• Dilated cardiomyopathy:
  • Exposure to toxins, including heavy metals, cobalt, organic solvents, and mercury
  • Nutritional deficiency involving thiamine, selenium, carnitine, or taurine and starvation
  • Endocrine disorders, including hypothyroidism, hyperthyroidism, adrenal cortical insufficiency, acromegaly, diabetes, and obesity
  • Electrolyte disturbances, including potassium deficiency and magnesium deficiency
  • Connective tissue disease, including systemic lupus erythematosus, polyarteritis nodosa, rheumatoid arthritis, scleroderma, and dermatomyositis
  • Hematologic disorders, including sickle cell anemia and thalassemia
  • Muscular dystrophies, including Duchenne, Becker, and myotonic types
  • Sarcoidosis
  • Idiopathic disease is diagnosed in a significant minority of cases
  • Smallpox vaccination (7.8 cases of myocarditis per 100,000 persons)
• Hypertrophic cardiomyopathy:
  • Idiopathic
• Restrictive cardiomyopathy:
  • Myocarditis
  • Cardiac transplantation
  • Pseudoxanthoma elasticum
  • Loeffler eosinophilic endomyocardial fibrosis
  • Gaucher disease (in children only)
  • Myocardial fibrosis following cardiac surgery
  • Radiation
  • Scleroderma
  • Endomyocardial fibrosis
  • Toxic effects of anthracyclines
  • Carcinoid heart disease and metastatic cancer

Risk factors

• Alcoholism
• Drug addiction
• HIV/AIDS
• Myocarditis
• Sarcoidosis
• Cancer affecting the heart or being treated with radiation or chemotherapeutic agents (increased risk of cardiomyopathy in patients with a preexisting decrease in systolic function receiving chemotherapy with anthracyclines)

Screening

It is important to screen all family members of patients with cardiomyopathy for hypertrophic cardiomyopathy.

Primary prevention

Avoidance of excessive alcohol consumption and abstinence from cocaine use can avert dilated cardiomyopathy due to these substances.