Cardiomyopathy, Dilated

Christopher P. Blomberg, D.O.

Basic Information

Definition

Dilated cardiomyopathy describes a group of diseases involving the myocardium and characterized by myocardial dysfunction that is not wholly the result of hypertension, coronary atherosclerosis, valvular dysfunction, congenital, or other structural heart disease. As a result, the heart is enlarged and the ventricles are dilated with impaired systolic function.

Synonyms

Congestive cardiomyopathy
Idiopathic cardiomyopathy

ICD-10CM CODES
B33.24	Viral cardiomyopathy
I11.0	Hypertensive heart disease with heart failure
I42.0	Dilated cardiomyopathy (includes congestive cardiomyopathy)
I42.9	Cardiomyopathy, unspecified (includes cardiomyopathy [primary] [secondary] NOS)
I43	Cardiomyopathy in diseases classified elsewhere
I50.20 to I50.9	(Unspecified, Acute, Chronic, or Acute on Chronic) + (systolic, diastolic, or combined) (congestive) heart failure
O90.3	Peripartum cardiomyopathy

Epidemiology & Demographics

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The estimated prevalence of dilated cardiomyopathy in the general adult population is approximately 1:2500. The incidence is approximately 4 to 8 per 100,000 persons per yr.
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The incidence of dilated cardiomyopathy is greatest in middle age and among men.
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African Americans have a three-fold increased risk for developing DCM, irrespective of comorbidities or socioeconomic factors, compared with whites.
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It is the most common cardiomyopathy and accounts for 25% of cases of congestive heart failure.

Physical Findings & Clinical Presentation

The patient will present with common symptoms of congestive heart failure, which may be of insidious or sudden onset. The patient may also be asymptomatic and the diagnosis made by the unexpected finding of cardiomegaly on a chest x-ray. The history should focus also on information that could help determine the etiology. Classical signs of heart failure may be absent. When present, findings are indistinguishable from other heart failure syndromes, including:

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Increased jugular venous pressure
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Narrow pulse pressure
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Pulmonary rales, hepatomegaly, peripheral edema
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S3, S4
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Mitral regurgitation, tricuspid regurgitation (less common)

Etiology

In approximate order of occurrence:

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Idiopathic (often a viral infection that cannot be confirmed)
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Infections (viral [human herpesvirus 6, influenza, echovirus, cytomegalovirus, Coxsackie B, adenovirus, parvovirus, HIV], rickettsial, mycobacterial, toxoplasmosis, trichinosis, Chagas’ disease)
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Alcoholism (15% to 40% of all cases in Western countries)
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Uncontrolled tachyarrhythmia (“tachycardia-mediated”)
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Sleep apnea–obstructive or nonobstructive
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Cirrhotic–not necessarily alcohol-induced
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End-stage renal disease–related
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Nutritional deficiencies–selenium, L-carnitine, thiamine
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Peripartum (greatest risk from last trimester of pregnancy to 6 months postpartum)
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Chemotherapeutic (anthracycline, doxorubicin, daunorubicin) or pharmacologic agents (antiretrovirals, phenothiazines) (see “Cardiomyopathy, Chemical-Induced”)
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Substance abuse (cocaine, heroin, organic solvents “glue-sniffer’s heart”)
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Postmyocarditis
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Toxins (cobalt, lead, phosphorus, carbon monoxide, mercury) Collagen-vascular disease (systemic lupus, rheumatoid arthritis, polyarteritis, dermatomyositis, sarcoidosis)
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Heredofamilial neuromuscular disease (e.g., muscular dystrophy)
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Excess hormones (acromegaly, osteogenesis imperfecta, myxedema, thyrotoxicosis, diabetes)
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Hematologic (e.g., sickle cell anemia, hemochromatosis, hypereosinophilia)
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Stress-induced (i.e., takotsubo or broken heart syndrome)
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LV noncompaction
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TTN truncating mutations (mutations in TTN, the gene encoding the sarcomere protein titin) are a common cause of dilated cardiomyopathy, occurring in approximately 25% of familial cases of idiopathic dilated cardiomyopathy and in 18% of sporadic cases.

Diagnosis

Dilated cardiomyopathy is a diagnosis of exclusion, made after ruling out other potential causes of myocardial dysfunction.

Differential Diagnosis

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Coronary atherosclerosis, that is, left ventricular dysfunction secondary to ischemia and/or myocardial infarction
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Valvular dysfunction (especially aortic and mitral regurgitation)
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Other cardiomyopathies (restrictive, hypertrophic)
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Pulmonary disease (embolism, obstructive, restrictive)
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Pericardial abnormalities (constrictive pericarditis, tamponade)
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Hypothyroidism/myxedema
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Athlete’s heart

Workup

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Medical history: emphasis on symptoms of dyspnea, orthopnea, paroxysmal nocturnal dyspnea, weight gain, palpitations, or signs of systemic and pulmonary embolism, substance abuse history, possible toxin exposures (especially occupational)
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Physical exam (see “Physical Findings & Clinical Presentation”)
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Testing (see “Laboratory Tests” and “Imaging Studies” for more detail): laboratory, chest x-ray, ECG, echocardiogram, cardiac catheterization; myocardial biopsy is not routinely recommended, unless acute myocarditis requiring immunosuppressive therapy is considered (e.g., giant cell myocarditis)

Laboratory Tests

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Chemistries/metabolites (deficiencies), renal function tests (renal dysfunction)
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Cardiac biomarkers (elevation of cardiac troponin or BNP)
1. 1.
  
  Persistently increased cardiac troponin T levels are a marker of poor outcome in cardiomyopathy patients
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Endocrine (particularly thyroid)
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Iron studies (hemochromatosis, deficiency)
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Rheumatologic and inflammatory (ANA, ESR, CRP)
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Others as indicated (HIV, Lyme, neurohormonal)

Imaging Studies

Chest x-ray:

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Cardiac silhouette enlargement (particularly left ventricle)
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Pulmonary vascular redistribution and congestion (Kerley B lines, cephalization of vasculature), pleural effusion (may appear as unilateral, most often on the right side)

ECG:

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ECG findings are typically nonspecific, and sinus tachycardia is usually a reflection of underlying heart failure. Large voltage in precordial leads and low voltage in limb leads may be seen in advanced disease.
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Intraventricular conduction defects and left bundle branch block
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Arrhythmias (atrial fibrillation, premature ventricular or atrial contractions, ventricular tachycardia)

Echocardiogram (Fig. E1):

FIG.E1

Dilated cardiomyopathy in a 19-year-old man with Duchenne muscular dystrophy.

A, ECG showing a QRS complex that is typical of Duchenne dystrophy, with tall R waves in V1 and deep, narrow Q waves in leads I and aVL. B, Two-dimensional echocardiogram (parasternal four chamber) showing a dilated, thinned left ventricle (LV).

From Bonow RO, et al.: *Braunwald’s heart disease—a textbook of cardiovascular medicine,* ed 9, St Louis, 2011, Saunders.

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Low ejection fraction with global hypokinesis
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Four-chamber enlargement (LV enlargement usually predominates)
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Mitral or tricuspid regurgitation (tethering due to incomplete leaflet closure caused by ventricular dilation)

Cardiac catheterization:

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On initial presentation to exclude obstructive epicardial coronary artery disease

Cardiac magnetic resonance imaging (CMRI):

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Particularly if infiltrative or inflammatory etiology suspected

Treatment

Nonpharmacologic Therapy

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Treatment of underlying disease (systemic lupus, alcoholism)
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Dietary sodium restriction (<2 g/day)
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Exercise training has been shown to be associated with reduced risk for hospitalization and death in patients with history of heart failure in limited trials; enrollment in a formal cardiac rehabilitation program may be beneficial in improving patient’s functional status

Acute General Rx

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Identify and treat the etiology of the acute exacerbation, when able. A helpful mnemonic is FAILURE: failure to take medications, anemia/arrhythmia, ischemia/infection/infarction, lifestyle (dietary indiscretion), upregulation of cardiac output (hyperthyroidism or pregnancy), renal failure, embolus (pulmonary).
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Diuretics are indicated for all patients with current symptoms or history of heart failure and reduced left ventricular ejection fraction (LVEF) with evidence of volume overload (see “Physical Findings and Clinical Presentation”) to improve symptoms. It is important to note that diuretics have not been shown to improve mortality rates.
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Patients with associated coronary atherosclerosis (angina, ECG changes, reversible defects on myocardial perfusion imaging) may benefit from percutaneous or surgical revascularization.

Chronic Rx

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Diuretics and digoxin as noted in “Acute General Rx.”
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ACE inhibitors (and angiotensin receptor blockers) have been shown to have favorable effects on ventricular remodeling in patients with cardiomyopathy and a demonstrable mortality benefit in these patients. They also reduce afterload and improve cardiac output. Therefore, they are recommended in all patients with reduced LV systolic function (EF ≤40%), regardless of symptoms unless specific contraindications exist.
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Beta-blockers work by inhibiting the adverse effects of the sympathetic nervous system in patients with ventricular systolic dysfunction (EF ≤40%). Only carvedilol, long-acting metoprolol succinate, and bisoprolol have shown a mortality benefit in patients with LV systolic dysfunction. Unless specifically contraindicated, they should be started after the acute exacerbation has resolved and titrated to the maximum tolerated dose.
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Aldosterone antagonists (spironolactone and eplerenone) have shown mortality benefit along with a decreased rate of hospitalization for heart failure in patients with symptomatic heart failure and reduced LV systolic function (EF ≤35%). They should be used following label guidelines and with close monitoring of renal function and potassium.
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Additional medical therapies (hydralazine/nitrates, digitalis) can be considered in certain patient subpopulations with persistent symptoms on otherwise optimal medical management.
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Digoxin has no mortality benefit but has been shown to improve patients’ quality of life in appropriately selected patients.
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The angiotensin receptor-neprilysin inhibitor sacubitril/valsartan (LCZ696 or Entresto™) in place of an ACE inhibitor or angiotensin receptor blocker and on top of optimal medical therapy in patients with class II-IV heart failure and an EF of 40% or less was found to significantly reduce multiple heart failure end points, including death, hospitalizations, and CV death in comparison to enalapril. This medication was approved in the U.S. in 2015.
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Ivabradine was FDA approved in 2015 for patients with stable, symptomatic chronic heart failure with left ventricular ejection fraction ≤35% who are in sinus rhythm with resting heart rates ≥70 beats/min and either of the following: (1) are on maximally tolerated doses of beta-blockers or (2) have a contraindication to beta-blocker use. It acts by blocking the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel responsible for the cardiac pacemaker I_f current, which regulates heart rate.

Disposition

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Annual mortality rate is 20% in patients with moderate heart failure, and it exceeds 50% in patients with severe heart failure. Once symptomatic, hospitalizations are frequent and readmission rates are high (>50% at 3 mo). A multispecialty treatment approach (e.g., primary care, cardiology, nutrition, cardiac rehabilitation) is recommended.

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Factors associated with an adverse outcome in dilated cardiomyopathy are described in Table 1.

TABLE1 Factors Associated with an Adverse Outcome in Dilated CardiomyopathyFrom Hare JM: The dilated, restrictive, and infiltrative cardiomyopathies. In Bonow RO, et al., (eds): Braunwald’s heart disease—a textbook of cardiovascular medicine, ed 9, St Louis, 2011, Saunders.

Clinical	Noninvasive	Invasive
NYHA Class III/IV	Low LV ejection fraction	High LV filling pressures
Increasing age	Marked LV dilation
Low exercise peak oxygen consumption	Low LV mass
Marked intraventricular conduction delay	≥Moderate mitral regurgitation
Complex ventricular arrhythmias	Abnormal diastolic function
Abnormal signal-averaged ECG	Abnormal contractile reserve
Evidence of excessive sympathetic stimulation	Right ventricular dilation or dysfunction
Protodiastolic gallop (S₃)
Elevated serum BNP
Elevated uric acid
Decreased serum sodium
BNP, Brain natriuretic peptide; ECG, electrocardiogram; LV, left ventricular; NYHA, New York Heart Association.

Referral

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Implantation of a cardiac defibrillator for primary prevention of sudden cardiac death can be considered for patients with LVEF <35% on optimal medical therapy regardless of symptom status. Emerging data have called into question the benefit of ICD implantation in patients with nonischemic heart failure (the DANISH Study), although these findings have not yet made it into the guidelines.
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Patients with LVEF <35%, left bundle branch block on ECG (QRS ≥0.13 sec), and persistent heart failure symptoms may benefit from cardiac resynchronization therapy via a biventricular pacemaker.
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Consider heart transplantation for relatively young patients (there is no precise age threshold) free of other significant comorbid conditions who are unresponsive to medical therapy. Dilated cardiomyopathy is the reason for 45% of all heart transplantations in the U.S.

Pearls & Considerations

Comments

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Patients should be encouraged to restrict or eliminate alcohol and reduce sodium intake (<2 g daily).
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Patients may benefit from daily weight checks as a means of early detection of volume overload and decompensated heart failure.
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Vulnerability to cardiomyopathy among chronic alcohol abusers is partially genetic and related to the presence of the ACE DD genotype.
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Idiopathic dilated cardiomyopathy is often familial, and apparently healthy relatives may have latent, early, or undiagnosed disease. Echocardiographic evaluation of family members is recommended.
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Incorporation of sequencing approaches that detect TTN truncations into genetic testing for dilated cardiomyopathy may substantially increase test sensitivity and allow earlier diagnosis of dilated cardiomyopathy.

Ferri – Cardiomyopathy, Dilated