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Dilated Cardiomyopathy

LV dilation with systolic dysfunction (reduced LVEF) in the absence of coronary artery disease or abnormal loading conditions sufficient to explain the degree of dysfunction

Review date
reviewed 2026-05-04
Reading time
5 min read
Author
Dr Kola Tytler MBBS CertHE MBA MSt MRCGP
Cardiovascularless-commonlong-term-condition
On this page
Condition details
Cardiovascular
less-common
5 min read
reviewed 2026-05-04
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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.

Key points

  • Defined by LV dilation + LVEF <40% without coronary disease or hemodynamic loading conditions to explain it
  • Most common cause of HFrEF requiring transplant. Etiologies: idiopathic (~50%), genetic/familial (~30%), alcohol, viral/post-myocarditis, peripartum, tachycardia-mediated, toxins (doxorubicin), thyroid
  • Workup: echo (dilated LV, globally reduced function), coronary assessment (angiography or CTA to exclude ischemic cause), cardiac MRI (fibrosis, infiltrative disease)
  • Treatment = HFrEF GDMT: ARNi + beta-blocker + MRA + SGLT2i + ICD if LVEF <=35% despite >=3 months therapy
  • Key reversible causes: alcohol (abstain), tachycardia-mediated (rate/rhythm control), peripartum (may recover), thyroid (treat), and takotsubo (resolves)

Overview

Dilated cardiomyopathy (DCM) is characterized by LV (and often RV) chamber dilation and systolic dysfunction in the absence of sufficient coronary artery disease or abnormal loading conditions to explain the impairment. It is the most common indication for heart transplantation. Approximately 30-50% of cases are familial, with autosomal dominant inheritance most common (mutations in titin, lamin A/C, desmoplakin, and others). The remainder includes post-viral/inflammatory, alcoholic, peripartum, drug-induced, and truly idiopathic forms.

Epidemiology

Incidence ~5-8 per 100,000/year. Men are affected more than women. Alcoholic cardiomyopathy typically requires >7-10 years of heavy drinking (>80 g/day). Peripartum cardiomyopathy occurs in the last month of pregnancy to 5 months postpartum, more common in African Americans, multifetal pregnancy, preeclampsia, and advanced maternal age. Tachycardia-mediated cardiomyopathy can occur with any sustained tachyarrhythmia (AF with rapid rate most common).

Clinical Features

Symptoms
Heart failure symptoms: dyspnea, orthopnea, PND, fatigue, edema
Palpitations (AF, PVCs, NSVT common)
Embolic events (stroke, peripheral embolism from LV thrombus)
Syncope or sudden death (VT/VF)
Signs
Signs of biventricular failure: JVD, crackles, peripheral edema, hepatomegaly
S3 gallop (volume overload)
Displaced PMI (LV dilation)
Functional MR murmur (annular dilation from LV enlargement)
Functional TR murmur (RV dilation)

Investigations

First-line
EchocardiogramLV dilation (LVEDD >5.5 cm), globally reduced LVEF, often 4-chamber dilation, functional MR/TR. Distinguish from HCM (hypertrophy without dilation) and restrictive (normal size, diastolic dysfunction)
ECGNon-specific: sinus tachycardia, LBBB (~25%), low voltage, atrial fibrillation, PVCs/NSVT
LabsBNP/NT-proBNP, CBC, BMP, LFTs, TSH, iron studies (hemochromatosis), HIV, hepatitis panel, alcohol level if relevant
Second-line
Coronary assessmentCoronary angiography or CTA to rule out ischemic etiology — CRITICAL distinction as ischemic cardiomyopathy may benefit from revascularization
Cardiac MRIMid-wall/epicardial LGE pattern (non-ischemic) vs subendocardial/transmural (ischemic). Identifies specific etiologies: myocarditis (epicardial LGE), sarcoid (patchy mid-wall), amyloid (diffuse subendocardial), iron overload (T2* mapping)
Specialist
Genetic testingConsider in all patients with non-ischemic DCM, especially with family history or conduction disease. Lamin A/C mutations associated with high arrhythmia risk (ICD at higher LVEF threshold)
Endomyocardial biopsyRarely needed — consider if giant cell myocarditis suspected (fulminant, rapidly progressive, VT), cardiac sarcoidosis, or eosinophilic myocarditis

Management

AHA/ACC/HFSA 2022 Heart Failure Guideline
1
Standard HFrEF GDMT
  • Same four pillars: ARNi + beta-blocker + MRA + SGLT2i — see Heart Failure page
  • ICD for primary prevention if LVEF <=35% despite >=3 months of GDMT
  • CRT if LVEF <=35% + LBBB + QRS >=150 ms
  • Anticoagulation if AF or documented LV thrombus
2
Treat reversible causes
  • Alcohol: complete abstinence — LVEF may recover substantially over 6-12 months
  • Tachycardia-mediated: rate/rhythm control of the causative arrhythmia — LVEF often normalizes within weeks to months
  • Peripartum: standard HFrEF GDMT (avoid ACEi/ARB if breastfeeding — use hydralazine + nitrate). Bromocriptine may be beneficial (experimental). ~50% recover LVEF within 6 months; subsequent pregnancy not recommended if LVEF does not recover
  • Thyroid: treat hyper- or hypothyroidism
  • Hemochromatosis: phlebotomy + chelation
  • Drug-induced (doxorubicin): dexrazoxane for prevention; no specific reversal once established

Complications

  • Progressive HF and death: 5-year mortality ~20% with modern GDMT
  • Sudden cardiac death: From VT/VF — ICD is protective
  • Thromboembolism: LV thrombus risk with severely reduced LVEF
  • Arrhythmias: AF, NSVT, sustained VT
USMLE Step 2 CK Exam Tips
  • 1Always rule out ischemic etiology (coronary angiography/CTA) before labeling as non-ischemic DCM — revascularization may improve LVEF
  • 2Alcohol cardiomyopathy is reversible with abstinence — always ask about alcohol intake in new HFrEF
  • 3Peripartum cardiomyopathy: last month to 5 months postpartum. ACEi/ARB contraindicated if breastfeeding
  • 4Tachycardia-mediated cardiomyopathy: any sustained tachyarrhythmia can cause DCM — control the rhythm/rate and LVEF improves
  • 5Lamin A/C mutation: high arrhythmia risk — consider ICD even at LVEF >35%
  • 6Cardiac MRI LGE pattern: mid-wall = non-ischemic DCM. Subendocardial = ischemic. Epicardial = myocarditis
  • 7Doxorubicin cardiomyopathy is dose-dependent and often irreversible — monitor with serial echos during chemotherapy

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Verified Sources & References

AHA/ACC/HFSA 2022 Heart Failure Guideline
ESC 2023 Cardiomyopathy Guideline
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