Cardiology > Dilated cardiomyopathy

Background

Dilated cardiomyopathy (DCM) is a myocardial disorder characterized by dilation and impaired contraction of one or both ventricles, most commonly the left. This leads to systolic dysfunction and often presents with symptoms of heart failure, arrhythmias, or thromboembolic events. DCM can be idiopathic or secondary to genetic mutations, infections, toxins, or systemic diseases. 

II) Classification/Types

By Etiology: 

• • Idiopathic (Primary): No identifiable cause; often presumed genetic 

• • Familial/Genetic: Mutations in sarcomeric, cytoskeletal, or nuclear envelope proteins 

• • Infectious: Viral myocarditis (e.g., Coxsackievirus), Chagas disease 

• • Toxic: Alcohol, cocaine, anthracyclines (e.g., doxorubicin), chemotherapy 

• • Metabolic: Hypothyroidism, thiamine deficiency, hemochromatosis 

• • Autoimmune/Inflammatory: Sarcoidosis, SLE 

• • Peripartum: Occurs in late pregnancy or postpartum 

• • Tachycardia-induced: From chronic uncontrolled arrhythmias 

• • Ischemic: Extensive coronary artery disease with prior myocardial infarction 

By Morphology: 

• • Dilated: Enlarged ventricular chambers with reduced ejection fraction 

• • Restrictive or Mixed Phenotypes: May overlap with other cardiomyopathy types in advanced cases 

By Severity (LVEF-based): 

• • Mild DCM: LVEF 45–50% 

• • Moderate DCM: LVEF 35–45% 

• • Severe DCM: LVEF <35% 

III) Pathophysiology 

DCM results from myocardial injury leading to myocyte death, wall thinning, and chamber dilation. This causes reduced systolic function, neurohormonal activation (RAAS, SNS), and progressive ventricular remodeling. It may also impair valve function (e.g., secondary mitral or tricuspid regurgitation), promote arrhythmias, and increase the risk of thromboembolism due to stasis. 

IV) Epidemiology

• • Sex: More common in men 

• • Age: Typically presents between ages 20–60 

• • Geography: Chagas endemic in Latin America; other causes worldwide 

• • Comorbidities: Hypertension, alcohol use, viral infections, genetic disorders 

Etiology

I) Causes

• • Idiopathic (~50% of cases) 

• • Genetic mutations (e.g., TTN, LMNA, MYH7) 

• • Myocarditis (viral, Chagas) 

• • Alcohol abuse 

• • Chemotherapy (e.g., doxorubicin) 

• • Postpartum state (peripartum cardiomyopathy) 

• • Tachyarrhythmias (e.g., atrial fibrillation, atrial flutter) 

• • Endocrinopathies (e.g., hypothyroidism) 

• • Nutritional deficiencies (e.g., thiamine) 

• • Connective tissue diseases 

• • Hemochromatosis or amyloidosis (infiltrative overlap) 

II) Risk Factors

• • Family history of cardiomyopathy or sudden cardiac death 

• • Alcohol or illicit drug use (especially cocaine) 

• • Prior viral illness 

• • Chemotherapy or radiation 

• • Autoimmune diseases 

• • Pregnancy (especially multiparous women) 

• • Uncontrolled arrhythmias 

• • Nutritional deficiency or malabsorption 

Clinical Presentation

I) History (Symptoms)

• • Fatigue, weakness 

• • Dyspnea on exertion, orthopnea, PND 

• • Peripheral edema, weight gain 

• • Palpitations or syncope (due to arrhythmias) 

• • Chest discomfort (not usually exertional) 

• • History of viral illness or alcohol use 

• • Sudden cardiac arrest (in familial cases) 

II) Physical Exam (Signs)

Vital Signs: 

• • Tachycardia 

• • Hypotension (in advanced disease) 

Cardiac Exam: 

• • Displaced, diffuse apical impulse 

• • S3 gallop (due to volume overload) 

• • Murmurs of mitral or tricuspid regurgitation (secondary) 

Pulmonary: 

• • Crackles or rales in pulmonary congestion 

• • Decreased breath sounds in pleural effusion 

Peripheral: 

• • Elevated JVP 

• • Pitting edema 

• • Ascites in right-sided involvement 

Differential Diagnosis (DDx)

• • Ischemic cardiomyopathy 

• • Restrictive cardiomyopathy 

• • Hypertrophic cardiomyopathy 

• • Pericardial diseases (e.g., constrictive pericarditis) 

• • Valvular heart disease 

• • High-output heart failure (e.g., anemia, thyrotoxicosis) 

• • Arrhythmogenic right ventricular cardiomyopathy 

• • Infiltrative diseases (e.g., amyloidosis, sarcoidosis) 

Diagnostic Tests

Initial Tests: 

• • Electrocardiogram (ECG): 

• • • Sinus tachycardia, arrhythmias, low voltage, conduction delays (e.g., LBBB) 

• • Chest X-ray: 

• • • Cardiomegaly, pulmonary congestion, pleural effusions 

• • BNP/NT-proBNP: 

• • • Elevated in heart failure 

Echocardiography: 

• • Confirms LV dilation and reduced systolic function 

• • Assesses MR/TR severity 

• • Excludes valvular pathology 

Cardiac MRI: 

• • Assesses myocardial fibrosis, inflammation 

• • Helps identify infiltrative or inflammatory causes 

• • Useful for prognostication 

Laboratory Tests: 

• • CBC, CMP, TSH, iron studies, viral serologies, autoimmune panel 

• • Cardiac enzymes (if suspecting myocarditis or infarct) 

Genetic Testing: 

• • Recommended in familial cases or early-onset disease 

Endomyocardial Biopsy: 

• • Rarely needed; may aid in suspected myocarditis, sarcoidosis, amyloidosis

     

Treatment

I) Medical Management

Guideline-Directed Heart Failure Therapy (HFrEF): 

• • ACE inhibitors/ARBs/ARNI (sacubitril-valsartan): Reverse remodeling 

• • Beta-blockers (e.g., carvedilol, metoprolol succinate): Mortality benefit 

• • Mineralocorticoid receptor antagonists (e.g., spironolactone): For NYHA II–IV 

• • SGLT2 inhibitors (e.g., dapagliflozin): Reduce HF hospitalization and death 

• • Diuretics: Symptom relief for congestion 

• • Ivabradine: For HR >70 bpm on max beta-blocker dose 

Anticoagulation: 

• • Consider if LV thrombus, atrial fibrillation, or history of embolism 

Antiarrhythmic Therapy: 

• • Beta-blockers or amiodarone for ventricular arrhythmias 

• • Avoid class I agents (proarrhythmic in structural disease) 

II) Devices/Interventions

• • ICD (Implantable Cardioverter-Defibrillator): 

• • • Indicated in EF ≤35% despite ≥3 months of therapy for primary prevention 

• • CRT (Cardiac Resynchronization Therapy): 

• • • Indicated for EF ≤35%, LBBB, QRS ≥150 ms, NYHA II–IV 

• • LVAD: 

• • • For end-stage disease as bridge to transplant or destination therapy 

• • Heart Transplant: 

• • • In refractory end-stage heart failure 

Patient Education, Screening, Vaccines

• • Educate on daily weights, salt restriction, medication adherence 

• • Discuss need for family screening in familial DCM 

• • Avoid alcohol and illicit drugs 

• • Avoid NSAIDs and noncompliance with diuretics 

• • Encourage regular physical activity (mild/moderate) 

Vaccinations: 

• • Annual influenza 

• • Pneumococcal 

• • COVID-19 

Consults

• • Cardiology: All patients with reduced EF or arrhythmias 

• • Electrophysiology: For ICD or CRT candidacy 

• • Advanced Heart Failure/Transplant Team: For refractory symptoms 

• • Genetics: For familial cases 

• • Infectious Disease: If myocarditis or Chagas suspected 

• • Primary Care/Internal Medicine: Comorbidity management 

Follow-Up

• • Echocardiography: Every 3–6 months to assess LV function 

• • Lab Monitoring: Renal function, electrolytes, BNP 

• • Device Checks: If ICD or CRT placed 

• • Exercise testing: To assess functional status and candidacy for advanced therapies 

• • Reinforce education: Early recognition of weight gain, dyspnea, palpitations 

• • Family Screening: 1st-degree relatives with ECG and echo