wide qrs tachycardias

WIDE QRS TACHYCARDIAS

Definition

Wide QRS tachycardia is a rhythm with a rate of more than 100 beats/min and having a QRS duration of > 120milliseconds (ms).

Why do we have widening of the QRS complex?

Any deviation in the normal pathway of ventricular activation may cause widening of the QRS complex.

WHY DO WE NEED TO DIFFERENTIATE THE ETIOLOGY OF WIDE QRS TACHYCARDIA?

Different pharmacologic management

For possible ablation Prognostication

Mechanisms for Wide QRS Tachycardia Supraventricular tachycardia (SVT) with

aberrant conduction Pre-excited tachycardia Ventricular tachycardia (VT) Pacemaker-mediated tachycardia

Supraventricular Tachycardia (SVT) with aberrant conduction

Conduction over the His-Purkinje system is blocked in either the right or the left bundle or the distal Purkinje system (intraventricular conduction delay).

Pre-excited tachycardia

ECG Assessment obtain a previous ECG if available important clues to differentiate VT vs SVT

- AV dissociation- fusion or capture beats- QRS width- QRS axis- QRS regularity- QRS concordance- QRS morphology

AV Dissociation independent atrial and ventricular

activation 50% of patients with VT rare in SVT best seen in leads V1 and inferior leads “Lewis” lead amplifies P waves

Capture and Fusion Beats dissociated P wave totally (capture) or

partially (fusion) activates the ventricle in advance of the next VT cycle

premature “narrow” QRS complex during VT

highly specific for VT

QRS Width consider VT if:

- RBBB pattern > 140 ms- LBBB pattern > 160 ms

QRS Axis

normal axis favors SVT left or right axis deviation favors VT extreme left or right axis deviation

(“northwest”) axis strongly favors VT

QRS Irregularity slight irregularity in the R - R interval may be

seen in SVT and VT marked irregularity of R - R interval suggests

atrial fibrillation conducted via accessory pathway

QRS Concordance strongly favors VT positive concordance (positive

QRS in V1 to V6) suggests posterobasal origin

negative concordance (negative QRS in V1 to V6) suggests anteroapical origin

Negative Concordance

Positive Concordance

QRS Morphology V1 and V6 most useful “typical” RBBB or LBBB pattern more

likely to be SV “atypical” pattern is more likely to be

VT abrupt change from one QRS

morphology to another during regular tachycardia suggests VT

QRS morphology during tachycardia similar to isolated PVC during sinus rhythm suggests VT

QRS Morphology Favoring SVT RBBB morphology QRS

- triphasic pattern with rsR` or rR` in V1- qRs in V6

LBBB morphology QRS- rS (r < 30 ms; rapid downslope of S) or QS in V1- monophasic R in V6

QRS Morphology Favoring VT•RBBB morphology QRS- monophasic or biphasic in V1; R > R’- rS or QS in V6

•LBBB morphology QRS- rightward axis- broad R wave (> 40 ms); notching in the

downslope of the S wave in V1

- qR or QS in V1

Brugada's sign: The interval from the R wave to the bottom of the S ways = 0.10 sec---characteristic VT

Josephson's sign: a small notching near the low point of the S wave = an indicator of VT

QRS MORPHOLOGYFavors SVT Favors VT

RBBB morphology

V1 TriphasicrsR’, rR’

MonophasicR>R’

V6 qRs rS or QS

LBBB morphology

V1 rS (r < 30 ms;) or QS

broad R (> 40 ms); notching of the SqR or QS in V1V6 monophasic R

Therapy for Wide QRS Tachycardia

if hemodynamically unstable, prompt electrical cardioversion is indicated

if stable and tachycardia mechanism is uncertain, therapeutic trial with:- adenosine- procainamide- lidocaine- Cardioversion

avoid verapamil unless VT has been ruled out with certainty

When in doubt, the working diagnosis is VT until proven otherwise!

INTERACTIVE SESSION

A 66M came in at the ER for severe chest heaviness and syncope. The patient’s syncope was due to:

A. Supraventricular tachycardia

B. Ventricular FibrillationC. Ventricular TachycardiaD. Atrial Fibrillation

Answer: C. Ventricular Tachycardia

After defibrillation, the ECG recording was as follows:

A. Supraventricular tachycardiaB. Ventricular Fibrillation C. Ventricular TachycardiaD. Atrial Fibrillation with

abberant conduction

Answer: C. Ventricular Tachycardia

Thank You