Wide QRS tachycardia

Raja Selvaraj. Professor of Cardiology, JIPMER

06-06-2020

Introduction

Definition

Straightforward. Definition is QRS width > 120 and rate > 100

What are the causes

Ventricular tachycardia
Supraventricular tachycardia
- Rate related aberrancy
- Preexisting bundle branch block
- Preexcited / antidromic tachycardia

Whole reason for discussing this topic is that SVT can also be wide Usually pacing and artifact are also included here

Why important to identify

Acute management
Long term management

Importance for initial treatment overemphasized. Initial treatment is more based on stable vs unstable Important however for long term management

VT vs SVT - Concept

Involvement of atria
- Usually part of tachycardia mechanism (SVT) - exceptions
- Not part of tachycardia mechanism (VT)
Use of specialized conducting system
- Ventricular activation uses HPS, but HPS conduction abnormalities (SVT with aberrancy)
- Ventricular activation originates outside of HPS (VT) - exceptions

Atrial involvement in tachycardia and Use of specialized conduction system to activate ventricles are the two main differences

VT vs Preexcited tachycardia - Concept

Both originate in ventricular muscle - Morphology cannot differentiate
Differences
- APs are restricted to specific locations
- Atrium involved in preexcited tachycardias

General approach

Sequential approach

Regularity
Atrial activation
Morphology
Sinus ECG
Response to AV blocking drugs / maneuvers

Approach in this sequence

Regularity

Sustained monomorphic VT and SVT usually very regular
Significant irregularity points to AF

Sometimes irregularity is subtle, AF may be missed if attention is not paid

Atrial activation

Number of P - less, equal or more
VA relationship - 1:1, other VA conduction, dissociation
Morphology of P - sinus / retrograde

P > QRS, P = QRS and P < QRS Better terminology than VA dissociation

Morphology

QRS width
LBBB like / RBBB like
Frontal axis
Morphology in V1 and V6
Early activation vs late activation

Morphology always less accurate

Morphology - Terminology

Morphology - Identify typical patterns

RBBB/LBBB, inferior axis, qS aVL and aVR - Outflow tract VT
RBBB / LAD, relatively narrow QRS - ILVT
LBBB / LAD - ARVC / Atriofascicular (Mahaim) pathway

Learn to identify some specific patterns

Sinus ECG

Evidence of MI - Correlate with VT origin
ARVC
Bundle branch block - SVT with aberrancy / BBRT
Preexcitation - AVRT with aberrancy / preexcited tachycardia

Adenosine

Termination
Transient slowing with AV block
No change

Cant emphasize enough the role of adenosine to make a diagnosis termination almost always suggests SVT transient slowing of ventricular rate with ongoing atrial tachycardia no change strongly suggests VT

Examples

52 M with palpitations

Dissociated sinus rhythm identified by following P waves capture and fusion beats

Dissociated, slower sinus rhythm

Ability to mark out the P waves at same intervals best proof of dissociation

35 F, repaired TOF

RBBB LAD P waves identified in break Identification of atrial activity confirms SVT

P waves are the key

After treatment with Dilzem

AV block with Dilzem confirms AT

35 M, Normal heart

thangavel ecg sca004.jpg

WQRS beats same as sustained tachy non reset indicates dissociation

thangavel ecg sca004_m.jpg

33 M with palpitations

Capture / fusion beats are narrow beats same as sinus or fusion of sinus and tachy that occur earlier than expected may see preceding p wave indicates dissociated atrial rhythm

35 M with palpitations

regular wqrst Possible intermittent VA dissociation lbbb / lad / qS V1, rS V6 neg precordial concordance. slow initial activation (r > 30, rS > 70)

ECG in sinus

T inv V1-V6 Epsilon waves

60 M

RBBB / LAD Initial activation rapid

Adenosine

Adenosine - slowing and narrow QRS P waves not well seen Response to adenosine suggests AV block with work

Dilzem

With Dilzem, atrial activity well seen Ongoing flutter

34 F, Palpitations and syncope

Classic preexcited AF Fast, Broad, Irregular Fusion beats Situation to avoid Adenosine

Sinus rhythm

Sinus rhythm - preexcitation can be identified

54 M, known CAD - old AWMI

kumar old mi sustained VT_001.jpg

RBBB LAD probable VA dissociation morphology - atypical RBBB, rS in V6, notched S in V2, V3 RBBB tachy in context of old MI

60 M, old AWMI

RAMADASS awmi svt CHANGES001.jpg

LBBB LAD LBBB with late transition - uncommon in MI sharp R, although slow RS

Adenosine

RAMADASS awmi svt CHANGES002.jpg

Elderly male

RBBB, normal axis Note incomplete RBBB in narrow beats Atrial tachycardia, CL matches for 2:1

30 F with paroxysmal palpitations

RBBB / RAD Slow initial activation / positive concordance Could be VT from basal LV or preexcited tachy with pathway at same place

Sinus ECG

Preexcitation of same morphology

Summary

WQRST - Can be VT or SVT
Atrial activation is key - A < V in VT, A > V is SVT
Morphology when A = V, but not very reliable
Learn in terms of concepts more than rules
Adenosine in stable tachycardia

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Wide QRS tachycardia Raja Selvaraj. Professor of Cardiology, JIPMER 06-06-2020