4th May 2025

Wide QRS Complex Tachycardias

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

Polymorphic VT

Background

Polymorphic VT is defined as an unstable rhythm with a continuously varying QRS complex morphology. A subtype of polymorphic VT is Torsades de Pointes (Twisting of the points) and is often precipitated by prolongation of the QT interval. Torsades de Pointes if left untreated can lead to Ventricular fibrillation.

Image Source: Wikimedia Commons (2011). Torsades converted by AICD ECG Strip Lead, Licensed under a creative commons licence. Available for free at: https://upload.wikimedia.org/wikipedia/commons/thumb/e/ed/Torsades_converted_by_AICD_ECG_strip_Lead_II.JPG/640px-Torsades_converted_by_AICD_ECG_strip_Lead_II.JPG (Accessed: 1 May 2025).

Causes of Long QT interval

Congenital

• Jervell-Lange-Nielsen syndrome (deafness)
• Romano-Ward syndrome (no deafness)
• Long QT syndrome

Drugs

• Sotalol, Amiodarone
• SSRIs (Citalopram)
• Tricyclic antidepressants (Amitriptyline)
• Antipsychotics (Haloperidol, Quetiapine, Risperidone)
• Azithromycin
• Ondansetron
• Methadone

Other

• Subarachnoid haemorrhage
• Hypokalaemia
• Hypomagnesaemia
• Hypocalcaemia
• MI
• Myocarditis

Medical management

• Unstable patients (haemodynamic compromise) need urgent shocking as for patients with monomorphic VT
• Pharmacological management is the same as that of monomorphic VT
• Correct underlying cause
• IV Magnesium Sulphate

Ventricular Fibrillation

VF is defined as rapid disorganised ventricular activity. This results in no uniform ventricular contractions and as a result leads to loss of cardiac output.

ECG shows a rapid ventricular rate of 300-400bpm. Over time, the amplitude of these irregular deflections decreases. (Coarse VF to fine VF).

Image Source: Wikimedia Commons (2020). Ventricular Fibrillation, Licensed under a creative commons licence. Available for free at: https://upload.wikimedia.org/wikipedia/commons/thumb/f/f1/Ventricular_fibrillation.png/640px-Ventricular_fibrillation.png (Accessed 1 May 2025).

Management

• Prompt defibrillation
• Reversal of underlying cause * Tricyclic Antidepressant overdose is treated with Sodium Bicarbonate solution*

Cardiac Arrest 

In cardiac arrest situations, following a systematic approach is crucial. Resuscitation council UK has given clear Advanced Life Support guidelines in cardiac arrest situations.

Once VF/Pulseless VT is identified on the monitor, the treatment would be delivering an immediate shock of 150-200J for the first shock. After 3 shocks via the defibrillator, Amiodarone 300mg IV and Adrenaline 1mg IV is given alongside cardio-pulmonary resuscitation.

Tachyarrhythmia algorithm *(adapted from Resus UK ALS algorithm 2021)*

References

1. https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis?search=wpw&source=search_result&selectedTitle=1~132&usage_type=default&display_rank=1
2. https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome?search=wpw&source=search_result&selectedTitle=2~132&usage_type=default&display_rank=2
3. https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia?search=avnrt&source=search_result&selectedTitle=1~73&usage_type=default&display_rank=1
4. https://bnf.nice.org.uk/treatment-summaries/arrhythmias/#ventricular-tachycardia
5. https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-in-patients-with-structural-heart-disease-treatment-and-prognosis?search=vt&source=search_result&selectedTitle=2~150&usage_type=default&display_rank=2
6. https://www.uptodate.com/contents/sustained-monomorphic-ventricular-tachycardia-clinical-manifestations-diagnosis-and-evaluation?search=vt&source=search_result&selectedTitle=4~150&usage_type=default&display_rank=4
7. https://bestpractice.bmj.com/topics/en-gb/409/treatment-algorithm
8. https://bestpractice.bmj.com/topics/en-gb/537
9. https://bestpractice.bmj.com/topics/en-gb/400
10. https://www.uptodate.com/contents/ventricular-arrhythmias-during-acute-myocardial-infarction-incidence-mechanisms-and-clinical-features?search=vf&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1
11. https://lms.resus.org.uk/modules/m25-v2-als-algorithm/11118/resources/chapter_6.pdf
12. https://www.resus.org.uk/sites/default/files/2021-04/Tachycardia%20Algorithm%202021.pdf