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 form of idiopathic ventricular tachycardia (IVT) arising from the LV outflow tract. It occurs in patients with no structural heart disease 🫀, usually in young or middle-aged adults, and generally has a benign prognosis compared with scar-related VT. 👉 Recognition is important because it can mimic dangerous VT but often responds well to ablation.

ℹ️ About

• LVOT Tachycardia: Originates from the left ventricular outflow tract region.
• Displays a Right Bundle Branch Block (RBBB) morphology on ECG due to LV origin. 📉
• Patients otherwise have normal cardiac imaging (Echo, CXR, CMR).

🧬 Aetiology & Mechanism

• Triggered activity or re-entrant arrhythmia within the LVOT. 🔄
• Occurs in the absence of structural heart disease.
• Episodes are usually monomorphic, repetitive, non-sustained or paroxysmal VT.
• Commonly precipitated by exercise 🏃‍♂️, stress, or catecholamine surges.

✅ Diagnostic Criteria

• No structural heart disease (Echo/CMR normal).
• Normal metabolic & electrolyte profile. 🧪
• No inherited arrhythmia syndromes (e.g. Long QT, Brugada, CPVT).

👩‍⚕️ Clinical Features

• Paroxysmal, exercise-induced sustained VT episodes. 🏋️‍♀️
• Palpitations 💓, dizziness, presyncope or syncope 😵.
• Episodes are alarming but usually well tolerated because the heart is structurally normal.
• Key OSCE point: Ask about exercise triggers and sudden palpitations in an otherwise healthy patient.

🧪 Investigations

• Blood Tests: Normal (exclude K⁺, Mg²⁺, thyroid).
• Echocardiography: Normal LV and RV structure & function. 🫀
• CXR: Typically normal.
• ECG during VT: • RBBB morphology (as it originates in LV). • S wave in lead I. • R-wave transition in V1/V2. • Inferior axis (origin at LVOT base). 📉 This ECG pattern helps localise origin to LVOT.
• Exercise Stress Testing: May provoke arrhythmia and confirm diagnosis.
• CMR: Used if ARVC, myocarditis or scar tissue suspected.

🚨 Note: Differentiating LVOT VT from other VT forms or SVT with aberrancy is difficult on surface ECG. 👉 Always treat as VT until idiopathic LVOT VT is confidently diagnosed by specialists.

💊 Management

• Initial Stabilisation:
  • Follow ABC protocol. 🫁
  • If unstable ➝ Immediate DC cardioversion ⚡.
• Acute Management:
  • Adenosine: 6–24 mg IV bolus ➝ effective in some catecholamine-sensitive LVOT VTs. 💉
  • IV Verapamil: 10 mg IV over 3–5 min (if LV function normal and diagnosis secure). ⚠️ Only under cardiology supervision; be ready to cardiovert if deterioration.
  • Beta-blockers: Can suppress adrenergic triggers and reduce recurrence.
• Long-Term Management:
  • Radiofrequency Catheter Ablation: Curative in ~90% of patients 🔥; first-line in drug-refractory or highly symptomatic LVOT VT.
  • Excellent prognosis once diagnosis made; sudden death is rare compared with scar VT ✅.

📚 References

• ESC – How to Recognise and Manage Idiopathic VT
• Melbourne Heart Rhythm – Idiopathic VT Ablation
• Additional peer-reviewed guidelines on idiopathic VT management.