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

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).