Cardiomyopathy, Dilated

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

Key Features

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

Clinical Findings

• 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

Diagnosis

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

  ...