Wide QRS tachycardia

Wide QRS tachycardia

wqt

Wide QRS Tachycardia

Electrocardiographic recognition of ventricular tachycardia (VT) by the presence of:

    1. A V dissociation – P waves randomly distributed
    1. Capture beats and fusion beats
  1. Monomorphic with concordant QRS pattern in chest leads

Sustained vs Nonsustained VT:

Sustained > 30 sec

Non-sustained at least 6 beats, but less than 30 sec

Types of LVOT VT: supracuspal vs infracuspal

Mechanisms of VT:

    1. Re-entrant: Types of re-entrant circuits: Anatomic, functional, anisotropic
    1. Automatic
  1. Triggered activity – Early after depolarisation and Delayed after depolarisation

Identification of VT – Tips

Septal VT has a relatively narrower QRS

If the QRS complex in tachycardia is narrower than in sinus rhythm it favors ventricular tachycardia originating from ventricle with the blocked bundle branch.

Concordant QRS in chest leads – Negative concordance in apical origin; Positive concordance in basal origin

LBBB pattern – RV or LV septum

RBBB – LV origin; RBBB pattern with abrupt loss of R wave seen in VT following anteroapical infarction

Fascicular VT: RBBB pattern, relatively narrower QRS complex, verapamil sensitive.

Posterior fascicular: left axis deviation; anterior fascicular: right axis deviation; septal fascicular VT: normal axis

Idiopathic Ventricular Tachycardia:

Absence of structural heart disease

Symptoms not generally severe

More often in young adults

May be an important cause of tachycardia

Cardiac arrest is rare

VT from RVOT usually occurs in salvoes (Gallavardin). No associated structural heart disease.

It has an LBBB morphology with right axis, exercise induced, catecholamine sensitive and adenosine sensitive due to the mechanism of triggered activity. ARVC also gives rise to VT mimicking idiopathic RVOT VT.

VT in the absence of structural heart disease:

RVOT / LVOT ventricular tachycardias and ILVT (Idiopathic Left Ventricular Tachycardia)

Channelopathies – LQTS, Brugada

Therapy in Long QT syndrome:

Beta blockers – highly effective

Pacemakers

ICD: Rochester ICD-LQTS registry: Interim data presented at HRS 2008:

Females had a higher discharge rate, Those with QT more than 500ms and a history of syncope had higher discharge rate. LQT2 had the maximum chance of ICD discharge. Dual mutation also conferred higher chance of ICD discharge.

Pacemakers useful in pause dependent torsades or if bradycardia develops due to beta blockers.

Who should get an ICD in Brugada syndrome?

Baseline abnormal ECG (without drug challenge), male patient and symptomatic patient have a higher risk. Inducible tachycardia also carries a higher risk.

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