Dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is the occurrence of ventricular dilatation and systolic dysfunction despite normal filling pressures, in the absence of coronary artery disease, abnormal loading pressures (e.g., valvular heart disease, hypertension), or congenital heart disease. It is the most common type of cardiomyopathy. Although most cases are idiopathic or inherited, DCM can also be caused by a number of conditions (e.g., endocrine disorders, autoimmune disease) and infections (e.g., Coxsackie B virus, Chagas disease) and by the use of certain substances (e.g., heavy drinking, cocaine). In DCM, decreased left ventricular contractility leads to left heart failure and eventually right heart failure with decreased ventricular output. Isolated dilation and subsequent decrease in right ventricular contractility is rare. Diagnosis is confirmed with echocardiography. Studies to evaluate the underlying etiology should be guided by clinical suspicion and include laboratory studies, genetic testing, advanced cardiac imaging, and, rarely, endomyocardial biopsy. Management involves treatment of the underlying condition and associated complications, e.g., congestive heart failure and arrhythmias. Severe or refractory disease may be managed with device implantation or cardiac transplantation.

Left or biventricular dilatation with structural and/or functional systolic dysfunction in the absence of coronary artery disease, abnormal loading pressures (e.g., valvular heart disease, hypertension), or congenital heart disease ^[1][2]

• Incidence: ∼ 6/100,000 per year (most common cardiomyopathy) ^[3][4]
• Sex: ♂ > ♀ (∼ 1.5:1) ^[5]
• Age at presentation: most commonly between 30 and 40 years of age, but can occur at any age ^[2]
• Ethnicity: more common in individuals of African descent ^[2]

Epidemiological data refers to the US, unless otherwise specified.

Primary causes

• Idiopathic ^[1]
• Familial, due to mutations in genes that encode components for sarcomeres and desmosomes, such as: ; ^[6][7]
  • TTN gene: encodes the intrasarcomeric protein titin (connectin)
  • MYH7 gene: encodes the beta-myosin heavy chain

Secondary causes ^[8]

• Substance use
  • Alcohol use disorder
  • Cocaine
  • Amphetamines
• Cardiotoxic medications, e.g., anthracyclines (such as doxorubicin and daunorubicin), AZT, trastuzumab
• Infection (infectious myocarditis)
  • Coxsackie B virus infection
  • Chagas disease
  • HIV infection
• Infiltrative and autoimmune disorders
  • Systemic lupus erythematosus
  • Sarcoidosis
  • Vasculitides, e.g., eosinophilic granulomatosis with polyangiitis, polyarteritis nodosa
• Hemochromatosis
• Peripartum cardiomyopathy (can occur in the last trimester or up to 6 months postpartum)
• Chronic tachycardia, e.g., atrial fibrillation
• Radiation ^[9]
• Endocrinopathies, e.g., pheochromocytoma, acromegaly, hyperthyroidism
• Neuromuscular diseases, e.g., myotonic dystrophy, Duchenne muscular dystrophy
• Nutritional deficiencies, e.g., thiamine (wet beriberi), selenium, carnitine

Volume and pressure overload secondary to conditions such as hypertension and valvular heart disease can cause dilation of the myocardium; however, these are not considered forms of DCM, as filling pressures are abnormal. ^[1]

To remember some high-yield secondary causes of dilated cardiomyopathy, think ABCCCDD: Alcohol use, Beriberi, Cocaine, Coxsackie B virus, Chagas, Doxorubicin/Daunorubicin

• Causative factors decrease the contractility of the myocardium → activation of compensatory mechanisms (Frank-Starling law) to maintain cardiac output → ↑ end-diastolic volume (preload) → myocardial remodeling → eccentric hypertrophy (sarcomeres added in series) and dilation of the ventricle ; → reduced myocardial contractility → systolic dysfunction and ↓ ejection fraction → heart failure
• Decreased LV contractility due to dilation leads to left heart failure and eventually right heart failure (see “Pathophysiology of congestive heart failure”).

Symptoms ^[1]

• Gradual development of symptoms of congestive heart failure
  • Dyspnea
  • Ankle and abdominal swelling
  • Angina pectoris
  • Fatigue
• Some patients may present with symptoms of arrhythmia.

Physical examination ^[11]

• Systolic murmur secondary to mitral valve regurgitation; or tricuspid valve regurgitation ^[12]
• S3 gallop
• Displacement of the apex beat
• Jugular venous distention
• Bilateral rales
• Peripheral edema
• Ascites

DCM is typically diagnosed during the workup for associated cardiac conditions (e.g., heart failure) or through screening of family members of patients with known or suspected familial DCM. ^[13]

Approach ^[8][14]

• Confirm the diagnosis on echocardiography.
• Rule out ischemic cardiomyopathy in patients with features of ischemic heart disease: See “Diagnostics for CAD.”
• Assess for complications, e.g., heart failure, arrhythmias. ^[7]
• Evaluate for the underlying etiology.
  • Strong family history of DCM: Perform genetic testing
  • Consider further testing based on clinical suspicion.
• Underlying etiology remains unclear:
  • Consider advanced studies (e.g., cardiac MRI or endomyocardial biopsy).
  • Consider evaluation for ischemic heart disease in patients > 35 years of age with DCM of unclear etiology.
• Idiopathic DCM: Refer for genetic counseling and testing to evaluate for a possible genetic etiology.

Echocardiography ^[14]

• Indications
  • To confirm the diagnosis of suspected DCM
  • To screen first-degree relatives of patients with familial DCM ^[1][8][14]
• Characteristic findings
  • Ventricular dilation with or without atrial dilation
  • Normal ventricular wall thickness ^[15]
  • ↓ Left ventricular ejection fraction (LVEF)
  • Wall motion abnormalities may be seen in some underlying etiologies (e.g., muscular dystrophy, acute myocarditis). ^[8][14]

Offer screening with a physical examination, ECG, and echocardiography (with assessment of left ventricular size and function) to first-degree relatives of patients with familial DCM. ^[7][14]

Initial diagnostic workup

Laboratory studies ^[8][14]

• CBC with differential ^[16]
• Basic metabolic panel
• Liver chemistries
• TSH
• HIV testing
• Ferritin, transferrin saturation
• Diagnostics for congestive heart failure: in patients with concomitant heart failure ^[14][17]
• Additional studies as needed for the underlying etiology as guided by clinical evaluation, such as:
  • Urine toxicology screen for suspected substance use
  • Inflammatory markers to detect autoimmune disease or myocarditis ^[8]
  • Specific serologies (e.g., for Lyme disease, Chagas disease)

Chest x-ray

• Indications: to assess for complications and the underlying etiology ^[17]
• Possible findings include:
  • Cardiomegaly: left-sided enlargement with a balloon appearance
  • Radiographic features of pulmonary edema secondary to decompensated heart failure
  • Findings of underlying disease, e.g., hilar lymphadenopathy in sarcoidosis ^[8]

ECG ^[8][18]

• Indications
  • To assess for complications (e.g., AV block)
  • To rule out tachycardia-induced cardiomyopathy
• Possible findings include ^[1][8]
  • Conduction disorders (e.g., AV block, LBBB)
  • Atrial fibrillation, other tachyarrhythmias
  • Reduced QRS voltage
  • ST-segment and T-wave abnormalities (e.g., T-wave inversions)

Holter monitoring

• Indications ^[14]
  • Arrhythmia symptoms
  • Abnormal ECG
  • Cardiomegaly on chest x-ray
• Possible findings include: ^[1]
  • Sinus tachycardia
  • Supraventricular arrhythmias
  • Premature ventricular contractions
  • Nonsustained ventricular tachycardia

Genetic testing ^[14]

• Recommended in:
  • Patients with suspected familial or idiopathic DCM
  • Family members of patients with DCM and an associated genetic mutation
• Consider in patients with DCM and any of the following: ^[8]
  • AV block on ECG
  • Elevations in:
    • Ferritin and/or transferrin saturation
    • Creatine kinase or cardiac biomarkers
  • Symptoms of neuromuscular disorders

Refer patients for genetic counseling prior to ordering genetic testing for DCM. ^[7]

Advanced studies ^[8][14]

Cardiac MRI

• Indications
  • Suspected infiltrative DCM (e.g., due to hemochromatosis, amyloid)
  • DCM of unclear etiology after the initial evaluation
  • Evaluation of cardiac function and morphology
• Findings
  • Myocardial edema: in active myocarditis and sarcoidosis ^[8]
  • Disease-specific pattern of gadolinium enhancement: e.g., in muscular dystrophy, sarcoidosis, Chagas disease ^[8]

Endomyocardial biopsy

• Indication: suspected underlying etiology that requires specific management (e.g., amyloidosis) and cannot be confirmed by other diagnostic methods
• Findings vary based on the underlying etiology.

• Interstitial fibrosis ^[19]
• Altered cardiomyocyte appearance ^[1]
  • Cell hypertrophy
  • Vacuole formation
  • Loss of myofibrils
  • Nuclear atypia

Overview ^[8][14]

• Treat the underlying cause of DCM: e.g., ; manage endocrine abnormalities, encourage abstinence from alcohol.
• Avoid cardiotoxic agents, if possible.
• Treat congestive heart failure, if present.
• In severe or refractory disease, consider:
  • AICD with or without cardiac resynchronization therapy
  • Left ventricular assist devices
  • Heart transplantation

Management of the underlying etiology ^[14]

Avoid immunosuppressants with potential cardiotoxicity (e.g., etanercept, infliximab) in patients with DCM. ^[14]

Management of complications

• Congestive heart failure ^[17][21]
  • Treat patients with DCM and heart failure with guideline-directed medical therapy. ^[14]
  • Nonpharmacological measures include sodium restriction, smoking cessation, restriction of alcohol consumption, and exercise (if able). ^[17]
• Arrhythmias: Management does not differ from standard best practice. ^[22]
  • See “Treatment of atrial fibrillation.”
  • See “Management of AV block.”
• Secondary mitral regurgitation: Consider mitral valve surgery. ^[23]
• Thromboembolic events: anticoagulation ^[24]
  • Indications: mechanical valves, intraventricular thrombus, and/or atrial fibrillation
  • Agents: warfarin, direct oral anticoagulants, heparins
  • The choice of anticoagulant and dosage vary based on the indication; for example dosages, see “Anticoagulation in atrial fibrillation.”

Severe or refractory DCM ^[17][21]

• Consider device implantation in selected patients with persistently low LVEF on optimized medical therapy.
  • If symptomatic with LVEF ≤ 35%: AICD (to prevent sudden cardiac death due to ventricular fibrillation)
  • If symptomatic with LVEF ≤ 35%, sinus rhythm, and QRS > 150 ms: cardiac resynchronization therapy (to improve contractility)
  • See “Invasive interventions” in “Treatment of heart failure” for additional eligibility criteria.
• DCM refractory to medical therapy and device implantation: Consider heart cardiac transplantation.
• Left ventricular assist devices can be considered as:
  • A bridge to transplant
  • An alternative therapy for refractory DCM in patients who are ineligible for transplant

DCM is the leading indication for heart transplantation. ^[25]

• Heart failure
• Thromboembolism (e.g., stroke, pulmonary embolism, acute mesenteric ischemia)
• Arrhythmias (e.g., atrial fibrillation, ventricular tachycardia, ventricular fibrillation)
• Sudden cardiac death

We list the most important complications. The selection is not exhaustive.

Dilated cardiomyopathy in pregnancy ^[15]

Planning pregnancy

• Generally, pregnancy is not recommended for patients with DCM and LVEF < 30% and/or NYHA class III or IV heart failure. ^[26]
• Consider exercise stress testing prior to pregnancy.
• For patients on ACEIs or ARBs, discontinue and assess cardiac function.
• In familial DCM, offer genetic counseling to discuss potential transmission.

During pregnancy

• Be aware of pregnancy restrictions on heart failure medications.
• Consult specialists (e.g., cardiology, obstetrics, maternal-fetal specialists) for the management of DCM.
• Monitor for symptoms of heart failure.

Avoid ACEIs, ARBs, and mineralocorticoid receptor antagonists during the preconception period and pregnancy. ^[15]