Dilated Cardiomyopathy (DCM)

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Patient Advice

Definition

Dilated Cardiomyopathy (DCM) is a condition characterised by the dilation and impaired contraction of one or both ventricles, leading to systolic dysfunction. It is a leading cause of heart failure and arrhythmias.

Aetiology

DCM can be caused by various factors, which may be genetic or acquired:

• Idiopathic: The most common cause where no identifiable cause is found.
• Genetic Mutations: Inherited forms are associated with mutations in genes encoding sarcomeric or cytoskeletal proteins.
• Infective: Viral myocarditis (e.g., Coxsackievirus or adenovirus).
• Toxic: Alcohol abuse, cocaine, or chemotherapeutic agents (e.g., doxorubicin).
• Metabolic: Conditions like hypothyroidism or diabetes mellitus.
• Autoimmune: Associated with diseases like systemic lupus erythematosus.
• Peripartum: Developing during pregnancy or postpartum.

Pathophysiology

DCM leads to a progressive cycle of cardiac dysfunction:

• Ventricular Dilation: The ventricle stretches, reducing contractile efficiency.
• Decreased Systolic Function: Impaired ejection of blood into the systemic circulation.
• Neurohormonal Activation: Activation of the RAAS and sympathetic nervous system leads to fluid retention and vasoconstriction.
• Remodelling: Structural changes exacerbate dysfunction and may lead to arrhythmias.

Risk Factors

Factors increasing the likelihood of DCM include:

• Family history of cardiomyopathy.
• History of myocarditis or viral infections.
• Excessive alcohol consumption.
• Use of cardiotoxic drugs.
• Systemic diseases like diabetes or autoimmune conditions.

Signs and Symptoms

Patients with DCM may present with:

• Dyspnoea: Shortness of breath, especially on exertion or lying flat.
• Fatigue: Reduced exercise tolerance and persistent tiredness.
• Peripheral Oedema: Swelling in the legs due to fluid retention.
• Palpitations: Awareness of an irregular or rapid heartbeat.
• Syncope: Fainting episodes, often due to arrhythmias.

Investigations

Key diagnostic tests and expected findings include:

• Electrocardiogram (ECG): May show non-specific changes, bundle branch block, or atrial fibrillation.
• Echocardiography: Demonstrates ventricular dilation and reduced ejection fraction.
• Chest X-ray: May show cardiomegaly or pulmonary congestion.
• Blood Tests:
  • Brain Natriuretic Peptide (BNP): Elevated in heart failure.
  • Thyroid Function Tests: To exclude metabolic causes.
  • Viral Serology: To assess for recent infections.
• Cardiac MRI: To evaluate myocardial structure and detect fibrosis or inflammation.
• Genetic Testing: For familial cases or if a genetic cause is suspected.

Management

1. Acute Management

• Oxygen Therapy: For hypoxia.
• Diuretics: Furosemide to relieve symptoms of fluid overload.
• Inotropes: E.g., dobutamine in severe cases to improve cardiac output.

2. Chronic Management

• Beta-blockers: E.g., bisoprolol to reduce myocardial workload.
• ACE Inhibitors: E.g., ramipril to prevent remodelling and reduce afterload.
• Mineralocorticoid Receptor Antagonists: E.g., spironolactone to reduce fluid retention.
• Anticoagulation: For patients with atrial fibrillation or thrombus formation.
• Implantable Cardioverter Defibrillator (ICD): For patients at high risk of arrhythmias.
• Cardiac Resynchronisation Therapy (CRT): For patients with significant conduction delays.

3. Specialist Referral

Referral to cardiology is essential for optimisation of medical therapy, advanced imaging, and consideration of device implantation or transplant evaluation.

Patient Advice

Key advice includes:

• Adhere to prescribed medications and attend regular follow-up appointments.
• Engage in low-impact exercise as tolerated and avoid overexertion.
• Maintain a healthy diet and limit sodium intake.
• Report worsening symptoms such as breathlessness, weight gain, or palpitations immediately.

Figure 1

Illustration showing the structural changes in Dilated Cardiomyopathy.

References

1. Blausen.com staff, Jmarchn and BruceBlaus (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. Available at: https://upload.wikimedia.org/wikipedia/commons/0/02/Blausen_0165_Cardiomyopathy_Dilated.svg (Accessed: 30 December 2024).