Ventricular Tachycardia

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

Definition

Ventricular Tachycardia (VT) is a life-threatening arrhythmia originating in the ventricles, characterised by a fast heart rate (≥100 beats per minute) with three or more consecutive ventricular beats. See Figure 1.

Aetiology

Causes of VT include:

  • Ischaemic Heart Disease: Commonly occurs post-myocardial infarction due to scarring in the heart muscle.
  • Cardiomyopathies: Conditions like dilated or hypertrophic cardiomyopathy.
  • Electrolyte Abnormalities: Low potassium or magnesium levels.
  • Drug Toxicity: E.g., digoxin toxicity or use of antiarrhythmics.
  • Genetic Conditions: E.g., Long QT syndrome or Brugada syndrome.

Pathophysiology

VT occurs due to abnormal electrical activity in the ventricles:

  • Re-entry Circuits: Electrical signals re-enter damaged areas, causing repetitive ventricular activation.
  • Enhanced Automaticity: Increased spontaneous electrical activity in ventricular cells.
  • Trigger Activity: Abnormal electrical signals triggered by afterdepolarisations.

Risk Factors

Factors increasing the risk of VT include:

  • Previous myocardial infarction.
  • Heart failure or reduced left ventricular ejection fraction (LVEF).
  • Electrolyte disturbances, e.g., low potassium or magnesium.
  • Family history of genetic arrhythmia syndromes.
  • Use of QT-prolonging medications.

Signs and Symptoms

Symptoms of VT include:

  • Palpitations: Sensation of rapid or irregular heartbeats.
  • Dizziness: Caused by reduced cardiac output.
  • Syncope: Sudden loss of consciousness due to inadequate blood flow to the brain.
  • Chest Pain: Due to reduced oxygen supply to the heart muscle.
  • Shortness of Breath: Due to decreased cardiac efficiency.

Investigations

Tests to diagnose VT include:

  • 12-Lead ECG:
    • Shows wide QRS complexes (>120 ms) and a fast ventricular rate.
    • Fusion or capture beats may indicate VT rather than supraventricular tachycardia (SVT).
  • Blood Tests:
    • Electrolytes: Check potassium, magnesium, and calcium levels.
    • Cardiac Markers: Elevated troponins may indicate myocardial ischaemia.
  • Echocardiography: Assesses ventricular function and identifies structural abnormalities.
  • Cardiac MRI: Evaluates scarring or fibrosis in the myocardium.
  • Electrophysiological Study (EPS): Maps abnormal electrical pathways and identifies re-entry circuits.

Management

1. Acute Management

  • Unstable VT: Immediate synchronised electrical cardioversion.
  • Stable VT: Antiarrhythmic medications such as amiodarone (300 mg IV loading dose, then 900 mg over 24 hours).

2. Long-Term Management

  • Implantable Cardioverter-Defibrillator (ICD): Device implanted to detect and treat VT episodes automatically.
  • Catheter Ablation: Procedure to destroy re-entry circuits in cases of recurrent or refractory VT.
  • Medication: Beta-blockers (e.g., bisoprolol) or antiarrhythmics (e.g., sotalol) to prevent recurrences.

3. Specialist Referral

Referral to cardiology is essential for:

  • Assessment for ICD implantation.
  • Evaluation for underlying causes, including ischaemia or cardiomyopathy.

Patient Advice

Key advice includes:

  • Avoid triggers such as stress, stimulants, and QT-prolonging medications.
  • Take medications as prescribed to prevent recurrence.
  • Maintain regular follow-up appointments to monitor heart health and device function if an ICD is implanted.
  • Seek urgent medical attention if symptoms like chest pain, syncope, or palpitations recur.

Figure 1

Ventricular Tachycardia ECG

Image showing an ECG example of ventricular tachycardia.

References

  1. BruceBlaus (2015). Ventricular Tachycardia [Image]. Available at: https://upload.wikimedia.org/wikipedia/commons/d/d4/Ventricular_Tachycardia.png (Accessed: 30 December 2024).
 
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