Cardiomyopathy, Dilated

For further information, see CMDT Part 10-44: Dilated Cardiomyopathy

Essentials of Diagnosis

• Symptoms and signs of heart failure

• Echocardiogram confirms left ventricular (LV) dilation, thinning, and global dysfunction

• Severity of right ventricular (RV) dysfunction critical in long-term prognosis

General Considerations

• Categorized as heart failure with reduced ejection fraction where the LV ejection fraction (EF) is defined as ≤ 40%

• Characterized by reduced myocardial contractility in the absence of abnormal loading conditions such as with hypertension or valvular disease

• Causes

  • Familial in up to 20–35% of cases

  • Idiopathic in a large proportion

  • Endocrine, inflammatory, and metabolic causes include

    • Obesity

    • Diabetes

    • Thyroid disease

    • Celiac disease

    • Systemic lupus erythematosus

    • Acromegaly

    • Growth hormone deficiency

  • Nutritional diseases, such as deficiency of thiamine, selenium, and carnitine

  • May also be caused by prolonged tachycardia either from

    • Supraventricular arrhythmias

    • Very frequent premature ventricular contractions (PVCs) (> 15% of heart beats)

    • Right ventricular pacing

  • Also associated with HIV, Chagas disease, rheumatologic disorders, iron overload, sleep apnea, amyloidosis, sarcoidosis, chronic alcohol usage, end-stage renal disease, or cobalt exposure ("Quebec beer-drinkers cardiomyopathy")

Demographics

• Prevalence averages 36 cases/100,000 in the United States and accounts for approximately 10,000 deaths annually

• Blacks are afflicted three times as often as whites

• Gradual development of heart failure symptoms in most patients

• Rales

• Elevated jugular venous pressure (JVP)

• Cardiomegaly

• S₃ gallop rhythm

• Murmurs of functional mitral or tricuspid regurgitation

• Peripheral edema

• Ascites

• Cheyne-Stokes breathing, pulsus alternans, pallor, and cyanosis may be present in severe heart failure

Imaging

• Chest radiograph reveals

  • Cardiomegaly

  • Evidence of left and/or right heart failure

  • Pleural effusions (right more frequently than left)

• Cardiac MRI

  • Diagnostic study of choice for right ventricular dysplasia

  • Helpful in identifying inflammatory or infiltrative processes, such as sarcoidosis or hemochromatosis

  • MRI with gadolinium can also help define an ischemic etiology by noting gadolinium hyperenhancement consistent with myocardial scar from infarction or prior myocarditis

Diagnostic Studies

• ECG

  • ST–T changes, conduction abnormalities, ventricular ectopy

  • Sinus tachycardia is common

  • Other common abnormalities include left bundle branch block and ventricular or atrial arrhythmias

• Echocardiogram

  • Indicated to exclude unsuspected valvular or other lesions and confirm the presence of ventricular dilatation, reduced LV systolic function and associated RV systolic dysfunction, or pulmonary hypertension

  • Mitral Doppler inflow patterns also help in the diagnosis of concomitant diastolic dysfunction

  • Color flow Doppler can reveal tricuspid or mitral regurgitation, and continuous Doppler can estimate pulmonary artery pressures

  • Intracavitary thrombosis is occasionally seen

• Exercise or pharmacologic stress myocardial perfusion imaging may uncover underlying coronary disease

• Radionuclide ventriculography

  • Provides a noninvasive measure of the EF and both RV and LV wall motion

  • However, its use has been supplanted by cardiac MRI in most institutions

• Cardiac catheterization

  • Seldom of specific value unless myocardial ischemia is suspected

  • However, right heart catheterization should be considered to help guide therapy when the clinical syndrome is not clear cut

• Myocardial biopsy

  • Rarely useful in establishing the diagnosis

  • However, the underlying cause (eg, sarcoidosis, hemochromatosis) can be discerned occasionally

  • Should not be used routinely

  • Most useful in transplant rejection

• See Heart Failure

• Standard therapy includes control of

  • Blood pressure

  • Contributing factors such as obesity, smoking, diabetes or potentially cardiotoxic agents

• All patients with a remote history of myocardial infarction or acute coronary syndrome and reduced LVEF should be given

  • Angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), or sacubitril/valsartan

  • β-Blockers

• All patients with dilated cardiomyopathy regardless of etiology should be treated with β-blockers and ACE inhibitors

• Aldosterone antagonists

  • Should be added with an angiotensin receptor-neprilysin inhibitor (ARNI) instead of ACE inhibitor or ARB when patient remains symptomatic

  • Using the combination of ACE inhibitor, ARB, and aldosterone antagonists is discouraged due to concerns of hyperkalemia

  • Should be added with diuretics if congestive symptoms are present

  • Should be added when the LVEF is < 35% in patients with class II–IV heart failure symptoms (unless contraindicated)

• Calcium channel blockers should be avoided except as necessary to control ventricular response in atrial fibrillation or flutter

• Mineralocorticoid receptor antagonists

  • Use cautiously when the glomerular filtration rate is < 30 mL/min/1.73 m² or when the potassium is elevated

  • Should be given to all patients with diabetes if the LVEF is ≤ 40%

• Ivabradine

  • Has been approved to slow the resting heart rate when it is > 70 beats per minute, the LVEF is < 35% and the patient has chronic stable heart failure

  • Should not replace other β-blockers, however

• Digoxin

  • Second-line medication but remains favored as an adjunct by some clinicians

  • May be beneficial to reduce recurrent hospitalizations and to control the ventricular response in atrial fibrillation in sedentary patients

• Cardiac rehabilitation and exercise training have consistently been found to improve clinical status

Prognosis

• Variable when patients do not have clinical heart failure

• Poor with 50% mortality at 5 years once symptoms emerge

• Once heart failure is manifest, the natural history is similar to that of other causes of heart failure, with an annual mortality rate of around 11–13%

• The underlying cause of heart failure has prognostic value in patients with unexplained cardiomyopathy

• Patients with cardiomyopathy due to infiltrative myocardial diseases, HIV infection, or doxorubicin therapy have an especially poor prognosis

When to Refer

• Patients with new or worsening symptoms of heart failure with dilated cardiomyopathy should be referred to a cardiologist

• Patients with continued symptoms of heart failure and reduced LVEF (35% or less) should be referred for consideration of placement of an implantable cardioverter defibrillator or cardiac resynchronization therapy (if QRS duration is 150 msec or more, especially with a left bundle branch block pattern)

• Patients with advanced refractory symptoms should be referred for consideration of heart transplant or LV assist device therapy

When to Admit

• Patients with hypoxia, fluid overload, or pulmonary edema not readily resolved in an outpatient setting should be admitted