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Dilated Cardiomyopathy

By Thomas D. Stamos, MD, Associate Professor of Medicine, Chief, Clinical Cardiology, University of Illinois at Chicago

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Dilated cardiomyopathy (DCM) is myocardial dysfunction causing heart failure in which ventricular dilation and systolic dysfunction predominate. Symptoms include dyspnea, fatigue, and peripheral edema. Diagnosis is clinical and by elevated natriuretic peptides, chest x-ray, echocardiography, and MRI. Treatment is directed at the cause. If heart failure is progressive and severe, cardiac resynchronization therapy, implantable cardioverter-defibrillator, repair of moderate to severe valvular regurgitation, or heart transplantation may be needed.

Pathophysiology

As a primary myocardial disorder, the myocardial dysfunction occurs in the absence of severe occlusive coronary artery disease or conditions that involve pressure or volume overload of the ventricle (eg, hypertension, valvular heart disease). In some patients, dilated cardiomyopathy is believed to start with acute myocarditis (probably viral in most cases), followed by a variable latent phase, a phase with diffuse necrosis of myocardial myocytes (due to an autoimmune reaction to virus-altered myocytes), and chronic fibrosis. Regardless of the cause, the myocardium dilates, thins, and hypertrophies in compensation (see Figure: Forms of cardiomyopathy.), often leading to functional mitral regurgitation or tricuspid regurgitation and atrial dilation.

The disorder affects both ventricles in most patients, only the left ventricle (LV) in a few (unless the cause is ischemia), and only the right ventricle (RV) rarely.

Mural thrombi may form once chamber dilation is significant, especially during the acute myocarditis phase. Cardiac tachyarrhythmias often complicate the acute myocarditis and late chronic dilated phases as may atrioventricular block. Atrial fibrillation commonly occurs as the left atrium dilates.

Etiology

Dilated cardiomyopathy has many known and probably many unidentified causes (see Table: Causes of Dilated Cardiomyopathy). More than 20 viruses can cause DCM; in temperate zones, coxsackievirus B is most common. In Central and South America, Chagas disease due to Trypanosoma cruzi is the most common infectious cause, although it is a cause of only 10% of heart failure cases in recent series. DCM is becoming increasingly common among patients with active HIV infection.

Other causes include prolonged tachycardia, toxoplasmosis, thyrotoxicosis, and beriberi. Many toxic substances, particularly alcohol, various organic solvents, iron or heavy metal ions, and certain chemotherapeutic drugs (eg, doxorubicin, trastuzumab), damage the heart. Frequent ventricular ectopy (> 10,000 ventricular premature beats/day) has been associated with left ventricular systolic dysfunction.

Sudden emotional stress and other hyperadrenergic states can trigger acute dilated cardiomyopathy that is typically reversible (as is that caused by prolonged tachycardia). An example is acute apical ballooning cardiomyopathy (takotsubo cardiomyopathy). In this disorder, usually the apex and occasionally other segments of the LV is affected, causing regional wall dysfunction and sometimes focal dilation (ballooning).

Genetic factors play a role in 20 to 35% of cases; > 60 genes and loci have been implicated.

Causes of Dilated Cardiomyopathy

Cause

Examples

Chronic tachycardia

Frequent ventricular ectopy

Uncontrolled atrial fibrillation or other persistent tachyarrhythmias

Connective tissue disorders

Drugs and toxins

Anthracyclines

Catecholamines

Cobalt

Cocaine

Cyclophosphamide

Psychotherapeutic drugs (tricyclic and quadricyclic antidepressants, phenothiazine)

Radiation

Trastuzumab

Eosinophilic myocarditis

Genetic abnormality

Familial disease in 20–30% of patients: autosomal dominant, X-linked, autosomal recessive, or mitochondrial inheritance

Granulomatous disorders

Granulomatous or giant cell myocarditis

Hereditary neuromuscular and neurologic disorders

Duchenne muscular dystrophy

Dreyfuss syndrome

Emery myotonia congenita

Fascioscapulohumeral muscular dystrophy

Friedreich ataxia

Infections (acute or chronic)

Bacterial

Fungal

Helminthic

Protozoan

Rickettsial

Spirochetal

Viral (including HIV infection)

Metabolic disorders

Acromegaly

Familial storage disorders

Hemochromatosis

Hypomagnesemia

Hypophosphatemia

Morbid obesity

Nutritional disorders (eg, beriberi, selenium deficiency, carnitine deficiency, kwashiorkor)

Uremia

Pregnancy (peripartum period)

Tumors

Certain endocrinologically active tumors (eg, pheochromocytoma, adrenal tumors, thyroid tumors)

Symptoms and Signs

Onset of dilated cardiomyopathy is usually gradual except in acute myocarditis, acute apical ballooning cardiomyopathy, and tachyarrhythmia-induced myopathy. About 25% of all patients with DCM have atypical chest pain. Other symptoms depend on which ventricle is affected.

Left ventricular dysfunction causes exertional dyspnea and fatigue due to elevated LV diastolic pressure and low cardiac output.

Right ventricular failure causes peripheral edema and neck vein distention. Infrequently the RV is predominantly affected in younger patients, and atrial arrhythmias and sudden death due to malignant ventricular tachyarrhythmias are typical.

Diagnosis

  • Chest x-ray

  • ECG

  • Echocardiography

  • Cardiac MRI

  • Endomyocardial biopsy (select cases)

  • Testing for cause as indicated

Diagnosis of dilated cardiomyopathy is by history, physical examination, and exclusion of other common causes of ventricular failure (eg, systemic hypertension, primary valvular disorders, myocardial infarction—see Table: Diagnosis and Treatment of Cardiomyopathies). Thus, chest x-ray, ECG, echocardiography, and, more recently, cardiac MRI are required. Endomyocardial biopsy is done in selected cases.

Serum cardiac markers are measured if acute symptoms or chest pain is present. Although typically indicative of coronary ischemia,troponin elevation often occurs in heart failure, especially if renal function is decreased. Serum natriuretic peptide levels are typically elevated when heart failure is present.

Specific causes suspected clinically are diagnosed (see elsewhere in The Manual). If no specific cause is clinically apparent, serum ferritin and iron-binding capacity and thyroid-stimulating hormone levels are measured.

Serologic tests for Toxoplasma, T. cruzi, coxsackievirus, HIV, and echovirus may be done in appropriate cases.

Chest x-ray shows cardiomegaly, usually of all chambers. Pleural effusion, particularly on the right, often accompanies increased pulmonary venous pressure and interstitial edema.

The ECG may show sinus tachycardia and nonspecific ST-segment depression with low voltage or inverted T waves. Sometimes pathologic Q waves are present in the precordial leads, simulating previous MI. Left bundle branch block and atrial fibrillation are common.

Echocardiography shows dilated, hypokinetic cardiac chambers and rules out primary valvular disorders. Segmental wall motion abnormalities can also occur in dilated cardiomyopathy because the process may be patchy. Echocardiography may also show a mural thrombus.

Cardiac MRI is increasingly done and is useful in providing detailed imaging of myocardial structure and function. MRI with gadolinium contrast may show abnormal myocardial tissue texture or scarring pattern (ie, late gadolinium enhancement, or LGE). The pattern of LGE can be diagnostic in active myocarditis, sarcoidosis, muscular dystrophy, or Chagas disease).

Positron-emission tomography (PET) has been shown to be sensitive for diagnosis of cardiac sarcoidosis.

Coronary angiography may be required to exclude coronary artery disease as the cause of LV dysfunction when the diagnosis is in doubt after noninvasive tests. Patients with chest pain or several cardiovascular risk factors and elderly patients are more likely to have coronary artery disease. Either ventricle can be biopsied during catheterization in select cases where the results will change management.

Endomyocardial biopsy is indicated if giant cell myocarditis, eosinophilic myocarditis, or sarcoidosis is suspected, as the results will affect management.

Prognosis

Prognosis generally has been poor, although prognosis has improved with current management regimens (eg, use of beta-blockers, ACE inhibitors, mineralocorticoid receptor antagonists, implantable cardioverter-defibrillators, or cardiac resynchronization therapy). About 20% die in the first year and then about 10%/yr thereafter; about 40 to 50% of deaths are sudden, due to a malignant arrhythmia or an embolic event. Prognosis is better if compensatory hypertrophy preserves ventricular wall thickness and is worse if ventricular walls thin markedly and the ventricle dilates. Patients whose dilated cardiomyopathy is well-compensated with treatment may be stable for many years.

Treatment

  • Cause (if any) treated

  • Anticoagulants when atrial fibrillation or other indication is present

  • Sometimes implantable cardioverter-defibrillator, cardiac resynchronization therapy (CRT), or transplantation

  • Immunosupression in patients with giant cell myocarditis, eosinophilic myocarditis, or sarcoidosis

Treatable causes (eg, toxoplasmosis, acute Chagas disease, hemochromatosis, thyrotoxicosis, beriberi) are corrected. Patients with HIV infection should have antiretroviral therapy (ART) optimized, Treatment with immunosuppression should be limited to patients with biopsy proven giant cell myocarditis, eosinophilic myocarditis, or sarcoidosis.

Otherwise, treatment is the same as for heart failure with reduced ejection fraction: ACE inhibitors, beta-blockers, aldosterone receptor blockers, angiotensin II receptor blockers, valsartan/sacubitril, hydralazine/nitrates, diuretics, and digoxin. Recent studies have shown patients with idiopathic dilated cardiomyopathy respond particularly well to standard HF treatments and generally do better than patients with ischemic heart disease.

Because mural thrombi may form, prophylactic oral anticoagulation has been used in the past. The use of anticoagulants for patients with reduced LV function and in sinus rhythm remains controversial, and recommendations regarding anticoagulant use in this situation await the results of ongoing clinical trials. Warfarin or a novel oral anticoagulant (NOAC) are recommended when a specific indication is present (eg, previous cerebrovascular embolism, identified cardiac thrombus, atrial fibrillation and/or flutter).

Medical treatment of heart failure reduces risk of arrhythmia, but an implantable cardioverter-defibrillator may be used to prevent death due to sudden arrhythmia in patients who continue to have a reduced ejection fraction despite optimal medical therapy. Because atrioventricular (AV) block during acute myocarditis often resolves, a permanent pacemaker is usually not needed acutely. However, a permanent pacemaker may be required if AV block persists or develops during the chronic dilated phase. If patients have a widened QRS interval with a low LV ejection fraction and severe symptoms despite optimal medical treatment, cardiac resynchronization therapy should be considered.

Patients with refractory heart failure despite treatment may become candidates for heart transplantation. Selection criteria include absence of associated systemic disorders and psychologic disorders and high, irreversible pulmonary vascular resistance; because donor hearts are scarce, younger patients (usually < 60) are given higher priority. Left ventricular assist devices (LVAD) may also be considered for destination therapy in some patients (eg patients who are not eligible for cardiac transplant). In destination therapy an LVAD is used as a permanent therapy for patients with refractory heart failure (rather than as a temporary measure before cardiac transplant).

Key Points

  • In dilated cardiomyopathy, the myocardium dilates, thins, and hypertrophies.

  • Causes include infection (commonly viral), toxins, and metabolic, genetic, or connective tissue disorders.

  • Do chest x-ray, ECG, echocardiography, and cardiac MRI to evaluate extent of disease and endomyocardial biopsy in select patients.

  • Look for other causes of heart failure if appropriate.

  • Treat primary cause if possible and use standard heart failure treatment measures (eg, ACE inhibitors, beta-blockers, aldosterone receptor blockers, angiotensin II receptor blockers, sacubitril/valsartan, hydralazine/nitrates, diuretics, digoxin, implantable cardioverter-defibrillator, and/or cardiac resynchronization therapy).

  • Use oral anticoagulants and immunosuppressants in select patients.

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