Makindo Medical Notes

Related Subjects: |Classical Ventricular Tachycardia |Idiopathic Ventricular Tachycardia |Right Ventricular Outflow Tract Tachycardia |Idiopathic Fascicular Left Ventricular Tachycardia |Left Ventricular Outflow Tract Tachycardia |Ventricular Fibrillation |Resuscitation - Adult Tachycardia Algorithm |Resuscitation - Advanced Life Support |Automatic Implantable Cardioverter Defibrillator (AICD)

Overview

Left Ventricular Outflow Tract (LVOT) Tachycardia is a type of idiopathic ventricular tachycardia that arises from the left ventricular outflow tract. It occurs in patients with no structural heart disease, and its management and prognosis differ from VT associated with underlying cardiac pathology.

About

• LVOT Tachycardia: A form of ventricular tachycardia originating from the left ventricle’s outflow tract.
• Typically displays a right bundle branch block (RBBB) pattern on the ECG, reflecting the direction of ventricular activation.
• Seen in patients with normal echocardiogram and chest X-ray findings.

Aetiology

• Results from a re-entrant arrhythmia mechanism in the absence of structural heart disease.
• Characterized by non-sustained, repetitive, monomorphic VT episodes, often triggered by exercise or stress.

Criteria

• No evidence of structural heart disease on imaging (e.g., normal echo and CXR).
• Normal metabolic and electrolyte profiles.
• Absence of congenital arrhythmogenic conditions such as long QT syndrome.

Clinical Features

• Typically presents as paroxysmal, exercise-induced sustained VT.
• Patients may experience syncope, palpitations, or dizziness during episodes.
• Despite rapid heart rates during episodes, the heart is anatomically normal.

Investigations

• Blood Tests: Routine blood work is usually normal.
• Echocardiography: Confirms normal cardiac structure and function.
• Chest X-ray (CXR): Typically shows no abnormalities.
• Electrocardiogram (ECG): Demonstrates VT with an S wave in lead I and an R-wave transition in leads V1 or V2, consistent with an LVOT origin.
• Exercise Stress Testing: May provoke the arrhythmia, aiding in diagnosis.

Note: Differentiating LVOT tachycardia from other forms of VT or from supraventricular tachycardia (SVT) with aberrancy can be challenging on a surface 12‐lead ECG.

Management

• Initial Stabilization:
  • Follow ABC protocols and assess hemodynamic stability.
  • If the patient is unstable, initiate immediate synchronized DC cardioversion.
• Acute Management:
  • Adenosine: Administer 6–24 mg IV in stable patients; effective if the arrhythmia is catecholamine-sensitive.
  • IV Verapamil: Administer 10 mg IV over 3–5 minutes in patients with normal left ventricular function, under cardiology supervision; be prepared for DC cardioversion if necessary.
  • Beta Blockers: May be used to suppress the arrhythmia and control the heart rate.
• Long-Term Management:
  • Radiofrequency Catheter Ablation: Recommended for patients with recurrent, symptomatic, or drug-refractory LVOT tachycardia, with cure rates approaching 90%.

References

• How to Recognise and Manage Idiopathic Ventricular Tachycardia
• Idiopathic VT Ablation Patient Information – Melbourne Heart Rhythm
• Additional guidelines and peer-reviewed articles provide further details on the management of idiopathic ventricular tachycardia.