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)

⚡ Idiopathic Ventricular Tachycardia (IVT) occurs in patients with a structurally normal heart. It has a different prognosis and management compared with scar-related or classical VT. 🚨 However, classic VT remains the most common cause of wide-complex regular tachycardia — always assume VT until a cardiologist proves otherwise.

ℹ️ About

• 🔽 Tachyarrhythmias originating below the AV node and bundle of His.
• 🩺 Differ in etiology, prognosis, and treatment from classical VT due to ischemic or structural heart disease.

🧬 Aetiology

• Mechanism may be automatic (triggered activity) or reentrant 🔄.
• Episodes often catecholamine-sensitive — triggered by exercise, infection, or stress 🏃‍♀️.

🆚 Idiopathic VT vs Classic VT

• 👴 Classic VT: Older patients with IHD or cardiomyopathy; poor prognosis.
• 📏 QRS width: Classic VT usually ≥140–200 ms; Idiopathic VT narrower, ~100–140 ms.
• 💊 Drug sensitivity: Idiopathic VT may respond to Adenosine or Verapamil ✅. ⚠️ These drugs can be dangerous in classic VT.
• 🔎 Idiopathic VT subtypes: RVOT, LVOT, Fascicular (posterior/anterior), ± rarer forms.

📊 Subtypes

• Right Ventricular Outflow Tract (RVOT) VT: LBBB morphology + inferior axis ⬇️; often adenosine-sensitive.
• Fascicular VT (Left-sided): Reentrant; • Posterior fascicle: RBBB + left axis deviation (most common, verapamil-sensitive). • Anterior fascicle: RBBB + right axis deviation. • Upper septal: rare, narrowest QRS.
• Left Ventricular Outflow Tract (LVOT) VT: RBBB pattern, often exercise-triggered.
• Bundle Branch Reentrant VT (BBRVT): Typically with structural heart disease, using His–Purkinje system as reentrant circuit.

👩‍⚕️ Clinical Features

• Occurs in younger, healthier patients vs classical VT.
• 💓 Palpitations, dizziness, presyncope/syncope.
• Severe hemodynamic collapse uncommon (heart is structurally normal).
• 📚 OSCE Pearl: Ask about exercise-induced palpitations in a young patient with normal echo.

🧪 Investigations

• Bloods: FBC, U&E, Ca²⁺, Mg²⁺, K⁺ all normal. 🧾
• ECG: QT interval normal. QRS narrower than classic VT (100–140 ms).
• Echo: Normal cardiac structure/function.
• CXR: Normal.
• Cardiac MRI: May be used to exclude subtle scar, ARVC, or myocarditis.

🚨 Remember: Classical VT is far more common. There is no perfectly reliable surface ECG test to distinguish idiopathic VT from scar VT or SVT with aberrancy. 👉 Always treat as VT until proven otherwise.

📑 Summary Table

💊 Management

• Initial Stabilisation: • ABC protocol. • If unstable ➝ urgent electrical cardioversion ⚡. • Early cardiology involvement.
• Acute Management: • Adenosine: Useful if catecholamine-sensitive VT. • IV Verapamil: Only in proven idiopathic VT with normal LV, under senior cardiology guidance. • Beta-blockers: Helpful in suppressing exercise/stress-triggered arrhythmias. • ⚠️ Never use Adenosine/Verapamil in suspected classical VT.
• Long-Term: • Radiofrequency Catheter Ablation: Highly effective (85–95% cure rate). • Prognosis excellent if diagnosis correct ✅.
• Important Note: Assume classical VT until cardiology confirms idiopathic VT.

📚 References

• Idiopathic Ventricular Tachycardias for the EM Physician
• ESC – Idiopathic Fascicular VT