Dilated Cardiomyopathy
Cardiology
Illness script · Cardiology
Dilated Cardiomyopathy
Ventricular dilation with systolic dysfunction (reduced EF) causing heart failure, often idiopathic or from identifiable insult.
This illness script for Dilated Cardiomyopathy covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Most common cardiomyopathy; leading cause of heart transplant
- Idiopathic (~50%) or familial (TTN, LMNA gene mutations)
- Alcohol abuse (chronic, dose-dependent myocyte toxicity)
- Peripartum: last month of pregnancy to 5 months postpartum
- Viral myocarditis (Coxsackievirus B, HIV, parvovirus B19)
- Doxorubicin/anthracycline toxicity; cocaine use; thyroid disease
02
Presentation
- Biventricular heart failure symptoms: dyspnea on exertion, orthopnea, PND, edema
- S3 gallop (hallmark of systolic dysfunction) + displaced PMI (lateral)
- Functional MR murmur: holosystolic at apex with radiation to axilla
- Fatigue and exercise intolerance (low cardiac output state)
- Risk of ventricular arrhythmias, sudden cardiac death, and mural thrombus/embolism
- EKG: LBBB pattern common; CXR shows cardiomegaly + pulmonary vascular congestion
03
Pathophysiology
- Myocyte injury → ventricular remodeling → chamber dilation and wall thinning
- Reduced contractility → decreased EF → compensatory neurohormonal activation (RAAS, SNS)
- Chronic neurohormonal activation worsens dilation and fibrosis (maladaptive remodeling)
- Dilated ventricle → mitral/tricuspid annular dilation → functional regurgitation → further volume overload
04
Diagnostics
- Echocardiogram: first-line — shows dilated LV with EF <40%, global hypokinesis
- Echo is also gold standard for diagnosis and monitoring response to therapy
- BNP/NT-proBNP: elevated, correlates with severity and guides therapy
- CXR: cardiomegaly (cardiothoracic ratio >0.5), Kerley B lines, pulmonary edema
- Cardiac MRI with gadolinium: best for myocarditis/fibrosis pattern; midwall late gadolinium enhancement suggests non-ischemic etiology
- Rule out ischemic CM: coronary angiography or stress imaging if CAD suspected
05
Management
- ACEi/ARB + beta-blocker (carvedilol/metoprolol succinate) + aldosterone antagonist — cornerstone GDMT
- SGLT2 inhibitors (dapagliflozin/empagliflozin) now standard of care in HFrEF
- Diuretics (furosemide) for volume overload symptom relief (not mortality benefit)
- ICD if EF ≤35% despite ≥3 months of GDMT, for sudden cardiac death prevention
- CRT (biventricular pacing) if EF ≤35% + LBBB + QRS ≥150 ms
- Anticoagulation if AF, LV thrombus, or EF very low; avoid negative inotropes (CCBs like verapamil)
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Ischemic Cardiomyopathy
DCM shows global hypokinesis on echo without regional wall motion abnormalities; ischemic CM has regional deficits corresponding to coronary territory.
Hypertrophic Cardiomyopathy
HCM features LV hypertrophy with preserved or hyperdynamic EF; DCM has dilation and reduced EF.
Cardiac Tamponade
Tamponade has elevated JVP with pulsus paradoxus and equalization of pressures but preserved/small ventricular chambers, not dilated.
Restrictive Cardiomyopathy
Restrictive CM shows normal or small LV size with preserved EF and diastolic dysfunction, not dilation or systolic failure.
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Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.