Dilated cardiomyopathy

Dilated cardiomyopathy
Synonyms	Congestive cardiomyopathy, idiopathic cardiomyopathy, primary cardiomyopathy
Pronounce	N/A
Field	Cardiology
Symptoms	Feeling tired, leg swelling, shortness of breath, chest pain, fainting
Complications	Heart failure, heart valve disease, irregular heartbeat
Onset	Middle age
Duration
Types	Tachycardia-induced, others
Causes	Genetics, alcohol, cocaine, certain toxins, complications of pregnancy, in many cases the cause remains unclear, certain infections
Risks
Diagnosis	Supported by electrocardiogram, chest X-ray, echocardiogram
Differential diagnosis	Coronary artery disease, heart valve disease, pulmonary embolism, other cardiomyopathy
Prevention
Treatment	Lifestyle changes, medications, implantable cardioverter defibrillator, cardiac resynchronization therapy (CRT), heart transplant
Medication	ACE inhibitor, beta blocker, diuretic, blood thinners
Prognosis	Five-year survival rate ~50%
Frequency	1 in 2500
Deaths

Illustration of a Normal Heart vs. Heart with Dilated Cardiomyopathy

Dilated cardiomyopathy on CT

Dilated cardiomyopathy on CXR

Serial 12-lead ECGs from a 49-year-old black man with cardiomyopathy.

VPC

Dilated cardiomyopathy (DCM) is a condition characterized by the enlargement and weakening of the heart's ventricles, leading to impaired pumping function. It is one of the most common types of cardiomyopathy and can result in heart failure, arrhythmias, and other serious complications.

Introduction to Dilated Cardiomyopathy

Dilated cardiomyopathy is a disease of the myocardium (heart muscle) in which the ventricles become enlarged (dilated) and weakened. This leads to a reduction in the heart's ability to pump blood efficiently throughout the body. The condition can occur at any age but is most commonly diagnosed in middle-aged adults.

History and Epidemiology

DCM was first described in the early 20th century as a non-ischemic form of heart failure unrelated to coronary artery disease. Over time, the understanding of its genetic and environmental causes has advanced significantly.

• Prevalence: DCM affects approximately 1 in 250 to 500 individuals globally, with variations depending on geographic and genetic factors.
• Mortality: If untreated, DCM can lead to severe complications, with a five-year mortality rate of up to 50% in advanced cases of heart failure.

Classification

Dilated cardiomyopathy is part of the broader category of cardiomyopathies, which are classified based on structural and functional abnormalities:

• 1. Primary DCM: Idiopathic, familial/genetic, or related to specific conditions like peripartum cardiomyopathy.
• 2. Secondary DCM: Associated with identifiable causes, such as toxins, infections, or metabolic disorders.

Pathophysiology

The pathophysiology of DCM involves:

• Ventricular dilation: Progressive enlargement of the heart's chambers, particularly the left ventricle.
• Reduced contractility: Impaired ability of the myocardium to contract, leading to systolic dysfunction.
• Neurohormonal activation: Compensatory mechanisms, such as the activation of the renin-angiotensin-aldosterone system (RAAS) and the sympathetic nervous system, initially support cardiac output but eventually contribute to worsening heart function.

Etiology

The causes of DCM are diverse and may be classified into:

• Genetic: Mutations in genes encoding proteins involved in the heart's cytoskeleton, sarcomere, or mitochondria. Familial DCM accounts for up to 30–50% of cases.
• Infectious: Myocarditis caused by viral, bacterial, or fungal pathogens.
• Toxic: Chronic exposure to alcohol, cocaine, or chemotherapeutic agents like doxorubicin.
• Autoimmune: Conditions such as systemic lupus erythematosus (SLE) or sarcoidosis.
• Metabolic: Diabetes, thyroid disorders, or nutritional deficiencies (e.g., thiamine deficiency).

Clinical Presentation

Symptoms of DCM vary depending on the stage and severity of the disease. Common presentations include:

• Mild cases: May be asymptomatic or cause nonspecific symptoms like fatigue or reduced exercise tolerance.
• Advanced cases: Symptoms of heart failure, including:
  • Dyspnea (shortness of breath)
  • Orthopnea (difficulty breathing while lying down)
  • Peripheral edema (swelling of the legs and ankles)
  • Jugular venous distension (JVD)

Diagnostic Criteria

The diagnosis of DCM typically involves: 1. Clinical Evaluation: Comprehensive history and physical examination.

2. Imaging Studies:

• Echocardiography: To assess ventricular dilation and reduced ejection fraction (EF).
• Cardiac MRI: For detailed evaluation of myocardial structure and fibrosis.

3. Laboratory Tests:

• Brain natriuretic peptide (BNP) or N-terminal pro-BNP levels: To assess heart failure severity.
• Screening for metabolic or infectious causes.

4. Genetic Testing: Recommended for patients with a family history of DCM.

Prognosis

The prognosis of DCM depends on factors such as the underlying cause, severity of left ventricular dysfunction, and response to treatment. Early diagnosis and management are crucial to improving outcomes.

Clinical Manifestations and Complications

Overview

The clinical manifestations of dilated cardiomyopathy (DCM) vary widely, ranging from asymptomatic cases to severe heart failure. The symptoms and signs depend on the degree of ventricular dysfunction, the presence of arrhythmias, and other systemic effects of the disease.

Symptoms

Patients with DCM often present with the following symptoms:

• Dyspnea: Shortness of breath during exertion or at rest, due to elevated pulmonary capillary wedge pressure.
• Orthopnea: Difficulty breathing while lying flat, often requiring patients to sleep with pillows.
• Paroxysmal Nocturnal Dyspnea (PND): Sudden episodes of severe shortness of breath that awaken patients from sleep.
• Fatigue: Resulting from reduced cardiac output and impaired perfusion of tissues.
• Palpitations: Due to arrhythmias such as atrial fibrillation or ventricular tachycardia.
• Edema: Swelling in the lower extremities or abdomen caused by fluid retention.

Less common symptoms may include:

• Syncope: Temporary loss of consciousness due to arrhythmias or reduced cardiac output.
• Angina: Chest pain, although less common in non-ischemic cardiomyopathy.

Physical Examination

Key findings on physical examination may include:

• Cardiac Signs:
  • S3 heart sound (indicative of ventricular dysfunction)
  • Displaced apical impulse
  • Murmurs due to mitral or tricuspid regurgitation
• Signs of Congestion:
  • Jugular venous distension (JVD)
  • Hepatomegaly
  • Pulmonary crackles
• Peripheral Findings:
  • Cool extremities
  • Pitting edema

Complications

DCM is associated with significant complications, which can worsen prognosis if not managed appropriately.

Heart Failure

DCM often leads to systolic heart failure, characterized by a reduced ejection fraction (EF). Symptoms include fluid overload, poor exercise tolerance, and hypoperfusion of organs.

Arrhythmias

• Atrial Fibrillation (AF): Common in DCM and associated with a higher risk of thromboembolism.
• Ventricular Arrhythmias: Ventricular tachycardia and ventricular fibrillation can cause sudden cardiac death (SCD).

Thromboembolism

• Stasis of blood in dilated ventricles increases the risk of clot formation.
• Emboli may lead to stroke, pulmonary embolism, or peripheral arterial occlusion.

Sudden Cardiac Death (SCD)

SCD is a major cause of mortality in DCM, often due to malignant ventricular arrhythmias. The risk is higher in patients with severely reduced EF.

Other Complications

• Valvular Regurgitation: Dilated ventricles can cause functional mitral or tricuspid regurgitation.
• Cardiorenal Syndrome: Impaired heart function may lead to kidney dysfunction.
• Infective Endocarditis: Rarely, patients with DCM and valvular regurgitation may develop endocarditis.

Risk Factors for Poor Prognosis

Several factors are associated with worse outcomes in DCM:

• Severe reduction in left ventricular ejection fraction (LVEF < 35%)
• Persistent symptoms despite optimal medical therapy
• Frequent hospitalizations for heart failure exacerbations
• Presence of arrhythmias, particularly ventricular tachycardia
• Significant comorbidities, such as diabetes mellitus or chronic kidney disease (CKD)

Diagnostic Workup

Patients with clinical features of DCM often require:

• Echocardiography: To assess ventricular size, systolic function, and valvular abnormalities.
• Electrocardiography (ECG): To detect arrhythmias, conduction delays (e.g., bundle branch block), or signs of myocardial injury.
• Chest X-Ray: To evaluate cardiac enlargement and pulmonary congestion.
• Cardiac MRI: Provides detailed imaging of myocardial fibrosis or scarring.
• Laboratory Tests: Include BNP, troponins, and screening for secondary causes like infections or metabolic disorders.

Diagnosis and Evaluation

Overview

The diagnosis of dilated cardiomyopathy (DCM) involves a combination of clinical evaluation, imaging studies, laboratory tests, and genetic assessments. Early and accurate diagnosis is essential to initiate appropriate management and improve patient outcomes.

Clinical Evaluation

The diagnostic process begins with a comprehensive history and physical examination.

Patient History

Key elements of the history include: Family History:

• • Presence of familial dilated cardiomyopathy or sudden cardiac death.
  • Genetic predispositions, such as mutations in sarcomere or cytoskeletal protein genes.

Symptom Assessment:

• • Onset, severity, and progression of heart failure symptoms, such as fatigue, dyspnea, and edema.

Exposure History:

• • Alcohol or substance abuse.
  • Exposure to cardiotoxic agents (e.g., anthracyclines).

Infectious History:

• • Recent viral infections suggestive of myocarditis.
• Comorbidities:
  • Presence of conditions like diabetes, hypertension, or autoimmune disorders.

Physical Examination

Key findings include: Cardiac Abnormalities:

• • S3 gallop (indicative of ventricular dysfunction).
  • Murmurs due to mitral or tricuspid regurgitation.

Signs of Congestion:

• • Jugular venous distension.
  • Pulmonary crackles.

Peripheral Signs:

• • Edema and cool extremities.
  • Cyanosis in severe cases.

Imaging Studies

Imaging plays a critical role in confirming the diagnosis and assessing the severity of DCM.

Echocardiography

• Transthoracic echocardiography (TTE) is the first-line imaging modality.

Key findings:

• • Enlarged left ventricle with reduced systolic function.
  • Left ventricular ejection fraction (LVEF) < 40%.
  • Functional mitral or tricuspid regurgitation.

Cardiac MRI

• Provides detailed evaluation of myocardial structure and function.
• Detects late gadolinium enhancement (LGE), indicative of fibrosis or scarring.
• Useful in differentiating DCM from other cardiomyopathies, such as hypertrophic cardiomyopathy.

Chest X-Ray

• Shows cardiac enlargement and signs of pulmonary congestion.
• May reveal pleural effusions in advanced cases.

Laboratory Tests

Laboratory evaluations are essential for identifying underlying causes and assessing disease severity.

Biomarkers

• Brain natriuretic peptide (BNP) or N-terminal pro-BNP (NT-proBNP):
  • Elevated levels indicate heart failure severity.
• Troponins:
  • Elevated in cases of active myocardial injury or myocarditis.

Screening for Secondary Causes

• Infectious Tests:
  • Viral serologies to identify potential myocarditis.
• Metabolic Panel:
  • Assess thyroid function (TSH, T3, T4) and nutritional deficiencies (e.g., thiamine deficiency).
• Autoimmune Panel:
  • Tests for antinuclear antibodies (ANA) or specific markers for sarcoidosis or lupus.
• Toxin Screening:
  • Evaluates for alcohol, cocaine, or chemotherapeutic agents.

Genetic Testing

• Genetic testing is recommended for patients with suspected familial DCM or a history of sudden cardiac death in first-degree relatives.
• Common mutations involve genes encoding proteins such as:
  • Lamin A/C (LMNA).
  • Titin (TTN).
  • Desmin (DES).

Genetic counseling is advised for patients and their families to guide further management and screening.

Electrophysiological Studies

Electrocardiography (ECG) and advanced electrophysiological testing can provide important diagnostic insights:

• ECG Findings:
  • Sinus tachycardia or bradycardia.
  • Conduction abnormalities (e.g., bundle branch block).
  • Ventricular arrhythmias or atrial fibrillation.
• Holter Monitoring:
  • Detects intermittent arrhythmias or paroxysmal episodes.
• Electrophysiological Testing:
  • Assesses the risk of sudden cardiac death and guides device therapy decisions.

Invasive Diagnostic Procedures

In selected cases, invasive testing may be required to confirm the diagnosis or rule out other conditions.

Endomyocardial Biopsy

• Performed to identify specific causes, such as myocarditis or infiltrative diseases (e.g., amyloidosis).
• Indicated in cases with unexplained heart failure or rapidly progressing disease.

Cardiac Catheterization

• Helps rule out ischemic cardiomyopathy by assessing coronary artery status.
• Evaluates hemodynamics in advanced heart failure.

Differential Diagnosis

Conditions that mimic DCM must be excluded:

• Ischemic Cardiomyopathy: Due to coronary artery disease.
• Hypertrophic Cardiomyopathy: Characterized by thickened ventricular walls.
• Restrictive Cardiomyopathy: Stiff ventricles without dilation.
• Peripartum Cardiomyopathy: Occurs during late pregnancy or postpartum.

Summary of Diagnostic Approach

• 1. Initial Evaluation: History, physical examination, and echocardiography.
• 2. Advanced Imaging: Cardiac MRI for structural details.
• 3. Laboratory Tests: Biomarkers and secondary cause screening.
• 4. Genetic Testing: For familial cases.
• 5. Invasive Testing: If indicated, for detailed evaluation.

Management and Prognosis

The management of dilated cardiomyopathy (DCM) focuses on alleviating symptoms, improving quality of life, and preventing disease progression and complications. Treatment strategies include lifestyle modifications, pharmacological therapy, device-based interventions, and in advanced cases, surgical options such as transplantation.

Lifestyle Modifications

Patients with DCM should adopt heart-healthy lifestyle changes to reduce disease burden and enhance overall well-being.

Diet and Nutrition

• Follow a low-sodium diet (<2,000 mg/day) to reduce fluid retention.
• Limit fluid intake in cases of hyponatremia or advanced heart failure.
• Avoid alcohol and recreational drugs, especially if they are contributing factors.

Physical Activity

• Encourage regular, moderate exercise to improve functional capacity and cardiac health.
• Avoid strenuous exercise or competitive sports in patients at risk for arrhythmias or sudden cardiac death.

Smoking Cessation

Complete cessation of smoking is critical, as smoking exacerbates cardiovascular disease.

Patient Education

Patients should be educated on:

• Recognizing early signs of decompensation (e.g., increased dyspnea, swelling).
• Adherence to prescribed medications and monitoring schedules.

Pharmacological Management

The cornerstone of DCM management involves evidence-based pharmacological therapies aimed at improving heart function and outcomes.

First-Line Therapies

• Angiotensin-Converting Enzyme (ACE) Inhibitors or Angiotensin II Receptor Blockers (ARBs):
  • Reduce afterload and improve symptoms.
  • Examples: Lisinopril, Losartan.
• Beta-Blockers:
  • Decrease heart rate, improve systolic function, and reduce mortality.
  • Examples: Carvedilol, Metoprolol succinate.
• Mineralocorticoid Receptor Antagonists (MRAs):
  • Prevent fluid retention and reverse cardiac remodeling.
  • Examples: Spironolactone, Eplerenone.

Second-Line Therapies

• Diuretics:
  • Provide symptomatic relief in fluid-overloaded patients but do not affect mortality.
  • Example: Furosemide.
• Digoxin:
  • May improve symptoms and reduce hospitalizations in selected patients.

Advanced Therapies

• Sodium-Glucose Co-Transporter-2 (SGLT2) Inhibitors:
  • Emerging evidence supports their role in reducing heart failure events.
  • Examples: Dapagliflozin, Empagliflozin.
• Ivabradine:
  • Used to lower heart rate in patients with sinus rhythm and heart rates >70 bpm despite beta-blocker therapy.

Device-Based Interventions

For patients with advanced DCM or specific complications, device therapy plays a critical role.

Implantable Cardioverter-Defibrillators (ICDs)

• Indicated for patients with a left ventricular ejection fraction (LVEF) ≤ 35% to prevent sudden cardiac death.
• Monitors and treats life-threatening arrhythmias.

Cardiac Resynchronization Therapy (CRT)

• Beneficial for patients with bundle branch block and heart failure with reduced ejection fraction (HFrEF).
• Improves ventricular synchrony and cardiac output.

Surgical and Advanced Therapies

For end-stage DCM, surgical interventions may be necessary.

Heart Transplantation

• The definitive treatment for selected patients with refractory heart failure.
• Requires lifelong immunosuppressive therapy.

Ventricular Assist Devices (VADs)

• Used as a bridge to transplantation or as destination therapy for patients ineligible for a transplant.
• Improves survival and quality of life in advanced heart failure.

Other Surgical Options

• Mitral Valve Surgery:
  • Corrects functional mitral regurgitation in cases where medical therapy is insufficient.
• Left Ventricular Reconstruction:
  • Considered for highly selected cases with severe ventricular remodeling.

Prognosis

The prognosis of DCM varies depending on:

• Severity: Patients with preserved ejection fraction and mild symptoms have better outcomes.
• Response to Treatment: Improved survival is observed with adherence to evidence-based therapies.
• Comorbidities: Coexisting conditions like diabetes or renal disease worsen prognosis.

Survival Rates

• One-year survival: Approximately 80–90%.
• Five-year survival: Around 50–60% for advanced cases.

Factors Influencing Prognosis

• Positive Indicators:
  • Early diagnosis and treatment.
  • Absence of severe arrhythmias or significant fibrosis on imaging.
• Negative Indicators:
  • Persistent heart failure symptoms despite therapy.
  • Recurrent hospitalizations or ventricular arrhythmias.

Current Research and Future Directions

Emerging research focuses on improving the management of DCM through:

• Gene Therapy:
  • Targeting specific mutations in familial DCM.
• Novel Drug Therapies:
  • Exploring agents that reverse myocardial fibrosis or enhance myocardial energetics.
• Artificial Intelligence (AI):
  • AI-driven algorithms to predict disease progression and optimize management.

Clinical Trials

Ongoing trials are investigating:

• Advanced imaging techniques for earlier diagnosis.
• Combination therapies for improved outcomes in heart failure.
• Biomarkers to predict arrhythmia risk.

See also

• Cardiomyopathy
• Heart failure
• Myocarditis

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