⚡ Idiopathic ventricular tachycardia (IVT) in patients with an anatomically normal heart is a distinct entity whose management and prognosis differs from ventricular tachycardia associated with structural heart disease. This is a specialist diagnosis and should not be confused with VT in the setting of cardiomyopathy. ✅

📖 About

A form of Idiopathic Ventricular Tachycardia (IVT).
💓 The most common idiopathic VT of the left ventricle, often arising from the Purkinje system.

🧬 Aetiology

Absence of structural heart disease 🫀.
Due to a re-entrant arrhythmia mechanism involving the fascicles of the left bundle branch.
Mainly affects males (60–80%), young to middle-aged (15–40 years). 👨

🔎 Forms (Subtypes)

Posterior fascicular VT (most common, ⬇️ axis).
Anterior fascicular VT (less common, ⬆️ axis).
Upper septal fascicular VT (rare, narrowest QRS).

✅ Diagnostic Criteria

No structural heart disease (confirmed by Echo/CMR).
No metabolic or electrolyte abnormalities (exclude hypoK/Mg, etc.).
No inherited arrhythmia syndromes (e.g., Long QT, Brugada, CPVT).

📊 Fascicular VT ECG Example

🩺 Classical VT is still the most common cause of wide-complex regular tachycardia. ❗ There is no perfectly reliable ECG method to distinguish classical VT from idiopathic VT or SVT with aberrancy. 👉 Always treat as VT until proven otherwise – follow the Adult Tachycardia (ALS) algorithm.

👩‍⚕️ Clinical Features

Typically young male adults (15–40 years).
Symptoms: palpitations 💓, dizziness, presyncope/syncope 😵, often triggered by exertion, febrile illness, or stress.
Usually well tolerated, unlike scar-related VT, but still causes functional limitation.

🧪 Investigations

🧾 Bloods: Normal (exclude electrolytes, thyroid).
🫀 Echocardiogram: Normal LV size and function.
📷 CXR: Normal.
🩺 12-lead ECG (baseline): QT normal, no structural abnormality.
📉 Acute ECG during VT: RBBB morphology, axis depending on subtype; QRS narrower (100–140 ms) compared to other VT.
💡 Cardiac MRI may be used to exclude subtle myocarditis, sarcoid or ARVC.

💊 Management

🔑 First principle: If in doubt, treat as classical VT and involve cardiology early.
🛑 ABC approach. If unstable ➝ DC cardioversion (per ALS). ⚡
👨‍⚕️ In stable, proven fascicular VT with normal LV function ➝ IV Verapamil 10 mg over 3–5 min under senior cardiology supervision (be ready to DC convert). ❗ NEVER use verapamil if diagnosis uncertain as it may be fatal in scar-related VT.
For recurrent but moderate symptoms ➝ Oral Verapamil (120–480 mg/day).
Radiofrequency catheter ablation 🔥 offers curative therapy in >90% of patients with symptomatic or drug-refractory VT.
💡 Unlike scar VT, idiopathic fascicular VT has an excellent long-term prognosis with low risk of sudden death once properly diagnosed and managed.

📚 References

ESC – Idiopathic fascicular left ventricular tachycardia

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Idiopathic Fascicular Left Ventricular Tachycardia