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Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is a medical condition characterised by an enlarged heart that cannot pump blood effectively. It can lead to severe complications such as heart failure, heart valve disease, and irregular heartbeat.

The condition often develops insidiously, and patients may initially remain asymptomatic. However, significant symptoms such as shortness of breath, fainting, and chest pain can eventually manifest.

Mouse heart slice showing dilated cardiomyopathy
Mouse heart slice showing dilated cardiomyopathy

Signs and Symptoms

DCM may not cause noticeable symptoms initially, but as the condition progresses, individuals may experience:

  • Shortness of breath
  • Syncope (fainting)
  • Angina, particularly in the presence of ischaemic heart disease

Physical examination may reveal an enlarged heart, pulmonary oedema, elevated jugular venous pressure, and low pulse pressure. Mitral and tricuspid regurgitation may also be detected.

Causes

The aetiology of DCM is diverse, with many cases having no apparent cause. Contributing factors include:

  • Genetic predispositions
  • Alcohol and cocaine use
  • Certain toxins and chemotherapeutic agents
  • Complications during pregnancy
  • Viral infections such as Coxsackie B virus
  • Autoimmune mechanisms
  • Thiamine deficiency
  • Thyroid disease
  • Inflammatory diseases like sarcoidosis and connective tissue diseases

Genetically, approximately 25–35% of cases are familial, with various mutations affecting genes encoding cytoskeletal proteins and other contraction-related proteins.

Pathophysiology

The progression of DCM involves left ventricular remodelling, characterised by gradual increases in left ventricular end-diastolic and end-systolic volumes, wall thinning, and a shift to a more spherical chamber geometry. This process is often associated with a decline in ejection fraction and is driven by compensatory mechanisms such as the Frank-Starling law and neurohormonal feedback.

Illustration of a Normal Heart vs. Heart with Dilated Cardiomyopathy
Illustration of a Normal Heart vs. Heart with Dilated Cardiomyopathy

Valvular Effects

As the ventricles dilate, mitral and tricuspid valves may fail to coapt properly, leading to regurgitation. This increases the risk of atrial fibrillation and exacerbates heart failure symptoms.

Diagnosis

Diagnosis of DCM involves several modalities:

  • Chest X-ray: Shows generalised heart enlargement and possibly pleural effusion.
  • Electrocardiogram (ECG): Reveals sinus tachycardia, atrial fibrillation, ventricular arrhythmias, left atrial enlargement, and intraventricular conduction defects.
  • Echocardiogram: Demonstrates left ventricular dilation with normal or thinned walls and reduced ejection fraction.
  • Cardiac catheterisation and coronary angiography: Used to exclude ischaemic heart disease.
  • Genetic Testing: Identifies mutations, especially in the TTN gene, which are linked to familial and sporadic cases.
Serial 12-lead ECGs from a patient with cardiomyopathy
Serial 12-lead ECGs from a patient with cardiomyopathy
Dilated cardiomyopathy on CXR
Dilated cardiomyopathy on CXR
Dilated cardiomyopathy on CT
Dilated cardiomyopathy on CT

Treatment

Medical Therapy

Treatment aims to manage symptoms and slow disease progression. Standard therapy includes:

  • Medications: ACE inhibitors, diuretics, beta-blockers, and anticoagulants.
  • Lifestyle Modifications: Salt restriction and adherence to prescribed medications.
  • Supplements: Coenzyme Q10 has shown some benefits.

Electrical Treatment

Patients with intraventricular conduction delay may benefit from artificial pacemakers, while those at risk of arrhythmia may require implantable cardioverter-defibrillators (ICDs). These devices help prevent sudden cardiac death and improve symptoms.

Surgical Treatment

For advanced cases unresponsive to medical therapy, heart transplantation may be considered, with 1-year survival rates approaching 90%.

Epidemiology

DCM affects approximately 1 in 2,500 people, with a higher prevalence in men and African-Americans. Onset typically occurs in middle age, but the condition can also affect children.

Research Directions

Research is ongoing into therapies that promote reverse remodelling, which may offer new approaches to improving the prognosis of cardiomyopathy patients.


Self-assessment MCQs (single best answer)

What is a characteristic feature of dilated cardiomyopathy?



Which of the following is NOT a common symptom of dilated cardiomyopathy?



What percentage of dilated cardiomyopathy cases are familial?



What is a common diagnostic tool used to visualise heart enlargement in DCM?



Which gene mutation is commonly associated with familial dilated cardiomyopathy?



What type of medication is commonly used in the treatment of DCM?



Which of the following conditions is a potential cause of dilated cardiomyopathy?



What is the primary goal of medical therapy in dilated cardiomyopathy?



Which diagnostic modality is used to exclude ischaemic heart disease in DCM patients?



What is the survival rate for heart transplantation in advanced DCM cases at 1-year post-operation?



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