Dilated Cardiomyopathy (DCM)

1. Definition

Dilated cardiomyopathy (DCM) is a myocardial disorder characterized by:

• Left ventricular (± right ventricular) dilation
• Systolic dysfunction (LVEF < 40%)
• Not explained by:
• Abnormal loading conditions (e.g., hypertension, valvular disease)
• Significant coronary artery disease (CAD)

 pathophysiology: impaired contractility → reduced cardiac output → neurohormonal activation → progressive remodeling

2. Epidemiology

• Leading cause of heart failure in younger patients
• Major indication for cardiac transplantation
• Male predominance (≈2–3:1)
• between the ages of 20 and 60

3. Etiology 

A. Genetic (30–50%)

• Most common mutation: TTN (titin truncating mutation)
• Others:
• LMNA (lamin A/C)
• MYH7 (β-myosin heavy chain)
• DSP (desmoplakin)

Typically autosomal dominant

B. Non-Genetic Causes

1. Infectious

• Viral myocarditis:
• Coxsackie B/Adenovirus/Parvovirus B19/HIV

2. Toxic

• Alcohol (most common reversible cause)
• Chemotherapy:Anthracyclines (e.g., Doxorubicin)
• Cocaine

3. Metabolic / Endocrine

• Thyroid disease/Diabetes
• Nutritional: -Thiamine deficiency (Beriberi)

4. Autoimmune / Inflammatory

• Sarcoidosis/SLE/Giant cell myocarditis

5. Peripartum cardiomyopathy

6. Tachycardia-induced cardiomyopathy

7. Idiopathic (most common overall)

4. Pathophysiology

Core Mechanism

• ↓ Contractility → ↓ Stroke volume → ↓ Cardiac output
• → Activation of:
• RAAS
• Sympathetic nervous system
• → Ventricular remodeling

Ventricular Remodeling

• LV dilation → eccentric hypertrophy
• Increased wall stress (Laplace law)
• Functional MR/TR due to annular dilation
• Arrhythmogenic substrate (fibrosis)

5. Clinical Features

A. Symptoms

• Dyspnea (exertional → rest)
• Orthopnea / PND
• Fatigue
• Palpitations
• Syncope (arrhythmia)

B. Signs

• S3 gallop (volume overload marker)
• Displaced apex beat
• MR murmur (holosystolic)
• Raised JVP-A-wave, large V waves,
• positive hepatojugular reflux.
• Peripheral edema

C. Complications

• Heart failure (HFrEF)
• Ventricular arrhythmias → sudden cardiac death
• Thromboembolism (LV thrombus)
• Cardiogenic shock

6. Investigations 

A. ECG

• Sinus tachycardia
• LBBB (important prognostic marker)
• Ventricular arrhythmias

B. Echocardiography 

• Dilated LV
• LVEF < 40%
• Global hypokinesia
• Functional MR

C. Cardiac MRI Diagnostic + Etiological

• Gold standard for tissue characterization
• Late gadolinium enhancement (LGE):
• Mid-wall fibrosis (septum) → classical DCM
• Helps differentiate from:
• Ischemic → subendocardial/transmural

D. Biomarkers

• BNP / NT-proBNP ↑
• Troponin (if active myocarditis)

E. Coronary Angiography

• To exclude ischemic cardiomyopathy

F. Genetic Testing

• Recommended in:
• Familial DCM
• Early onset
• Conduction disease

 EVALUATION FOR SECONDARY CAUSES OF DCM (Mandatory WORKUP)

7. Diagnostic Criteria

A. LV Dilation

• LV end-diastolic diameter (LVEDD):
• >2 SD above normal for age, sex, body size
• OR indexed LVEDD >117% of predicted value
• LV volumes increased:
• LVEDV ↑, LVESV ↑
• Must be true dilation, not just apparent due to volume status

B. Systolic Dysfunction

• LVEF < 40% (classic definition)
• Some guidelines:<45% (early/mild DCM spectrum)

C. Exclusion of Secondary Causes 

DCM diagnosis requires EXCLUSION of:

1. Ischemic heart disease

• No significant CAD:
• No ≥50% stenosis in major epicardial vessels
• Must be ruled out by:
• Coronary angiography / CT coronary angiography

2. Abnormal loading conditions

• Long-standing:
• Hypertension
• Valvular disease (MR, AR, AS)
• Congenital heart disease

DIFFERENTIATION FROM OTHER CARDIOMYOPATHIES

8. Management (GUIDELINE-DIRECTED MEDICAL THERAPY – GDMT)

Principle: Treat as HFrEF (ESC 2023 / ACC 2022)

STEP 1: INITIATE “FOUR PILLARS” (Class I, strongest recommendation)

1. ARNI (Preferred) / ACEi / ARB

 First-line: ARNI (Sacubitril + Valsartan)

• Starting: 24/26 mg BD (low BP/renal) OR 49/51 mg BD
• Target: 97/103 mg BD

 Titration:

• Double dose every 2–4 weeks

 Special:

• Stop ACEi → wait 36 hrs before starting ARNI
• Monitor: K⁺, creatinine

If ARNI not possible → ACE inhibitor

• Enalapril
• Start: 2.5 mg BD
• Target: 10–20 mg BD

OR ARB (if ACEi intolerance):

• Valsartan: 40 mg BD → 160 mg BD

 ACEi/ARB reduce mortality significantly

Note-Target dose = the dose of a drug proven in large clinical trials to give maximum mortality benefit in heart failure (DCM/HFrEF).

2. Beta-blockers (MANDATORY)

ONLY 3 evidence-based:

• Carvedilol
• Bisoprolol
• Metoprolol succinate

Doses:

 Titration:Increase every 2 weeks

 Start ONLY if:

• Euvolemic
• No acute decompensation

 Strong mortality reduction evidence

 3. Mineralocorticoid Receptor Antagonist (MRA)

• Spironolactone:
• Start: 12.5–25 mg OD
• Target: 25–50 mg OD
• Eplerenone:
• 25 mg OD → 50 mg OD

 Indication:LVEF ≤35%

 Monitor:K⁺ (hyperkalemia risk)

 Reduces mortality & hospitalization

 4. SGLT2 Inhibitors (NEW GOLD STANDARD)

• Dapagliflozin: 10 mg OD
• Empagliflozin: 10 mg OD

✔ No titration needed
✔ Works even WITHOUT diabetes

 Now standard in all HFrEF/DCM

STEP 2: SYMPTOM CONTROL (CONGESTION)

Diuretics (Loop)

• Furosemide:
• Start: 20–40 mg OD/BD
• Titrate based on urine output
• Torsemide: 10–20 mg OD

 ONLY for symptom relief (no mortality benefit)

 Used for fluid overload

STEP 3: ADD-ON THERAPIES (BASED ON PROFILE)

 Ivabradine

• Dose: 5 mg BD → 7.5 mg BD
• Indication:
• Sinus rhythm
• HR ≥70 despite max beta-blocker

 Hydralazine + Nitrates

• Hydralazine: 25–75 mg TDS
• Isosorbide dinitrate: 20–40 mg TDS

 Use if:

• ACEi/ARB intolerance
• Persistent symptoms

 Mortality benefit in selected patients

 Digoxin

• Dose: 0.125–0.25 mg OD

Use:Persistent symptoms

• AF with HF

 No mortality benefit, only symptom control

 Anticoagulation

• Indications:
• AF
• LV thrombus
• EF <30% (selected cases)

 STEP 4: DEVICE THERAPY 

 ICD (Implantable Cardioverter Defibrillator)

• Indication:
• LVEF ≤35%
• ≥3 months optimal therapy

 CRT (Cardiac Resynchronization Therapy)

• LVEF ≤35% + LBBB + QRS ≥150 ms

Prevents sudden cardiac death & improves survival

 STEP 5: ADVANCED THERAPY

 For refractory cases:

• LVAD
• Heart transplant

 Lifestyle Modification

• Salt restriction (<2 g/day)
• Fluid restriction (1.5–2 L/day)
• Avoid alcohol, cardiotoxins

Trials 

• SOLVD trial enalapril heart failure
• PARADIGM-HF trial sacubitril valsartan
• MERIT-HF trial metoprolol succinate

References

1.Mahmaljy H, Yelamanchili VS, Singhal M. Dilated Cardiomyopathy. [Updated 2023 Apr 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441911/