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
Epidemiology
Etiology
Primary causes
- Idiopathic
- Familial, due to mutations in genes that encode components for sarcomeres and desmosomes
- TTN gene: encodes the intrasarcomeric protein titin (connectin)
Secondary causes
- Substance use
- Alcohol use disorder
- Cocaine
- 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
- Hemochromatosis
- Peripartum cardiomyopathy (can occur in the last trimester or up to 6 months postpartum)
Mnemonic
To remember some high-yield secondary causes of dilated cardiomyopathy, think ABCCCDD: Alcohol use, Beriberi, Cocaine, Coxsackie B virus, Chagas, Doxorubicin/Daunorubicin
Pathophysiology
Decreased LV contractility due to dilation leads to left heart failure and eventually right heart failure
Clinical features
Diagnostics
- Echocardiogram (ECHO): Definitive diagnostic tool. Shows LV dilation and ↓ Ejection Fraction (EF), typically <40%.
- CXR: Cardiomegaly (globular silhouette), pulmonary edema/congestion.
- ECG: Non-specific findings; may show LBBB, arrhythmias (e.g., atrial fibrillation).
- Labs: ↑ BNP (B-type natriuretic peptide) reflects ventricular stretch and is a marker for HF severity.
- Pathology
- Gross: Enlarged, heavy, and “flabby” heart with dilation of all four chambers.
- Micro: Myocyte hypertrophy with interstitial fibrosis.
Treatment
Complications
- Heart failure
- Thromboembolism (e.g., stroke, pulmonary embolism, acute mesenteric ischemia)
- Arrhythmias (e.g., atrial fibrillation, ventricular tachycardia, ventricular fibrillation)
- Sudden cardiac death