4th May 2025

Ventricular Tachycardia

Background

Ventricular tachycardia (VT) is a broad complex tachycardia originating from the ventricles.  It is also defined by having a cardiac rhythm with a rate >100bpm and a QRS width >120ms. 

VT occurs as there are regions of slowed conduction in the ventricle allowing the opportunity to develop reentrant arrhythmias. This process can be caused by any structural abnormality in the ventricle. In post myocardial infarction patients, ventricular scars from infarction or fibrosis provide a substrate for this process.

Risk factors for developing Monomorphic VT

• Coronary ischaemic heart disease (especially prior MI)
• Hypertrophic cardiomyopathy
• Dilated cardiomyopathy
• Arrhythmogenic right ventricular cardiomyopathy

ECG features

Image Source: Wikimedia Commons (2020). Lead Generated Ventricular Tachycardia, Licensed under a creative commons licence. Available for free at: https://upload.wikimedia.org/wikipedia/commons/thumb/4/45/12_lead_generated_ventricular_tachycardia.JPG/640px-12_lead_generated_ventricular_tachycardia.JPG (Accessed 1 May 2025).

Features suggestive of VT rather than SVT with aberrancy

• RSR’ complexes with a taller “left rabbit ear”
• Very broad QRS complex >160ms
• AV dissociation
• Positive or negative concordance in precordial leads
• Fusion or capture beats
• Marked left axis deviation
• Absence of typical RBBB or LBBB morphology

Even with the use of algorithms, differentiating VT vs SVT with aberrancy can still be challenging. Therefore, in an emergency, broad complex tachycardias are to be treated as ventricular in origin.

* Verapamil should NOT be given in a broad complex Tachycardia, as it may precipitate Ventricular Fibrillation in patients with VT * As this may precipitate electrical impulses travelling down an aberrant pathway in SVT’s with a bundle branch block.

Medical management

Unstable patients

• Synchronised DCCV

Stable patients

• Amiodarone
• Lidocaine
• Procainamide