January 3, 2016

Wide QRS Tachycardia

An adult patient came in due to palpitations. What is the rhythm?

Figure 1

What is a Wide Complex Tachycardia?

A wide complex tachycardia (WCT) is defined as a cardiac rhythm with  a rate ≥ 100 bpm and QRS width/duration 120 ms or 0.12 sec. Other terms used aside from WCT is wide QRS tachycardia or WQRST. 

A WCT is also defined by the V1 morphology. So, a WCT can have a right bundle branch block (RBBB) configuration or left bundle branch block configuration. A RBBB is recognized by a QRS duration  120 ms with a predominantly positive portion in V1. LBBB has a QRS duration of 120 ms with a predominantly negative  terminal portion in V1.

WCT can be:

Ventricular Tachycardia (VT)

Supraventricular tachycardia (SVT):
A) with aberrancy in the His-Purkinje system
B) with anterograde accessory pathway conduction
C) with bizarre baseline QRS
D) in presence of drug effect or electrolyte imbalance

Ventricular pacing

Electrocardiogram artefact

VT requires the participation of structures below the bundle of His while SVT requires the participation of structures above the bundle of His.

Why take the time to differentiate WCT?

The purpose of arriving at the correct diagnosis is to avoid harm to the patient. If SVT is treated as VT and given amiodarone or electrical cardioversion may not be harmful but not the optimal therapy. If it was atrial flutter, cardioversion will entail a risk of stroke.  If VT is treated as SVT (using diltiazem/verapamil), hemodynamic deterioration may occur. If SVT are managed as VT, they might be placed on long-term amiodarone which carries a number or long-term problems. We should also not fall into the trap that stable patients (minimal symptoms) with WCT have SVT or unstable patients with WCT are VT. Also, we should not fall into the belief that a WCT terminated by adenosine or verapamil is SVT because some VT are sensitive to these drugs.

So, we go back to the patient and the long time dictum to treat the patient and not the monitor. If the patient is unstable then immediate cardioversion and then if the patient is stable then the various algorithms are used.

Table 1 Predictive Values and Accuracies of the Most Common Ventricular Tachycardia Criteria

Others would just say treat a WCT as VT because by prevalence alone we will be correct 4 out 5 times because pre-test probability that a WCT being VT is in excess of 80%. However, it will defeat the reason of having warm thinking body and avoiding harm to our patients.

As we can observe, most algorithms differentiating VT from SVT with aberrancy focus on characteristics unique to VT. If those characteristics are not present, then it is presumed SVT until proven. Also, we should recognize that algorithms find it hard to distinguish VT from pre-excited SVT.

VT description

In SVT, the relationship to the R the P is used to classify into 2 big groups (short RP or long RP SVT). In VT, the QRS morphology is used. It could either be RBBB WCT or LBBB WCT. This is done by observing the terminal deflection in V1. If the terminal deflection is negative then it is LBBB and if the terminal deflection is positive then it is RBBB WCT.

Here is a very educational graphic from Drs. Garner J and Miller J. 

Figure 2 - Morphological Criteria Discriminating VT from SVT from Garner J and Miller J.

Using the different criteria for the case

  • Brugada algorithm - RS interval > 100 ms (120 ms in V5 and V6) = VT

Figure 3 - RS interval > 100 ms

  • Morphologycal criteria for VT - 

V1-  BIphasic QRS - QR
V6 - R:S ratio < 1

Figure 4 - V1 and V6

  • aVR algorithm (aka Vereckei) - Vi/Vt in V6 0.1/0.4 < 1 = VT

  • Bayesian approach - right superior axis, qR in V1 = VT

  • RWPT criteria - V1 50 ms = VT

Back to the case

This is a regular wide QRS monomorphic tachycardia with right bundle branch (RBBB) morphology and right superior axis at cycle length 400 ms (~ 150 bmp).

This is sustained monomorphic ventricular tachycardia, emanating from the left ventricular focus. Amiodarone was given terminating the tachycardia. It was also found out the EF was low and AICD was offered.


Brugada et al. 1991. A New Approach to the Differential Dx of a Regular Tachycardia with a wide QRS Complex.Circ 83:1649-1659 - http://circ.ahajournals.org/content/83/5/1649.full.pdf+html

Bonnow et al. 2014. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 10th Edition. PA.Saunders 

Drew B and Scheinman M. 1995. ECG Criteria to Distinguish Between Aberrantly Conducted Supraventricular Tachycardia and Ventricular Tachycardia: Practical Aspects for the Immediate Care Setting. PACE 18:2194-2208

Garner J and Miller J. 2013. Wide Complex Tachycardia – Ventricular Tachycardia or Not Ventricular Tachycardia, That Remains the Question. Arrhythmia & Electrophysiology Review 2(1):23–29

Miller et al. 2006. The Value of 12-Lead ECG in Wide QRS Tachycardia Cardiology Clinics 24:439-451

Sandle and Marriot.1965.The Differential Morphology of AnomalousVentricular Complexes of RBBB-Type in Lead V1 Ventricular Ectopy versus Aberration. Circulation 31: 551-556

Stahmer SA and Cowan R. 2006. Tachydysrhythmias. Emergency Medicine Clinics of North America 24:11-40


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