Wide QRS Tachycardias
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Transcript of 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