ECG features suggesting epicardial origin of VT

ECG features suggesting epicardial origin of VT

ECG features suggesting epicardial origin of VT: ECG criteria suggesting epicardial origin of ventricular tachycardia can be divided into interval criteria and morphology criteria.

Interval criteria

All the interval criteria are based on the fact that there will be initial QRS widening when the ventricular tachycardia originates from an epicardial focus. This is because the epicardial focus is away from the Purkinje network while endocardial foci are nearer the Purkinje network.
Important interval criteria indicating an epicardial origin of the ventricular tachycardia are:

1. Intrinsicoid deflection time more than or equal to 85 msec
2. Shortest RS complex ≥121 ms
3. Maximum deflection index ≥0.55

Intrinsicoid deflection time more than or equal to 85 msec
Intrinsicoid deflection time is measured from the earliest ventricular activation to the peak of the R wave in V2.
Shortest RS complex ≥121 ms
RS duration is measured from the onset of the ventricular activation to the nadir of the S wave in any of the precordial leads.
Maximum deflection index ≥0.55
Maximum deflection index is the duration from the earliest activation to the peak of the largest amplitude deflection divided by the total QRS duration, measured in precordial leads.

Morphology criteria

1. Q waves in lead I and no q waves in inferior leads
2. Pseudo delta wave ≥34 ms

Q waves in lead I and no q waves in inferior leads
q wave in lead I is one of the most sensitive criteria indicating an epicardial origin of the ventricular tachycardia.¹ It would indicate an initial rightward activation from the left ventricular basal epicardial region. The criterion has a sensitivity and specificity of eighty eight percent. Absence of q waves in inferior leads had a sensitivity of ninety four percent to suggest epicardial origin of ventricular tachycardia.

Pseudo delta wave ≥34 ms
Pseudo delta wave duration is taken from the earliest ventricular activation to the onset of the earliest fast deflection, measured in any precordial lead. Pseudo delta wave represents the transmural activation time from the epicardial region to the endocardial region where the conduction system is located.²

References

1. Vallès E, Bazan V, Marchlinski FE.  ECG criteria to identify epicardial ventricular tachycardia in nonischemic cardiomyopathy. Circ Arrhythm Electrophysiol. 2010 Feb;3(1):63-71.
2. Berruezo A, Mont L, Nava S, Chueca E, Bartholomay E, Brugada J. Electrocardiographic recognition of the epicardial origin of ventricular tachycardias. Circulation. 2004 Apr 20;109(15):1842-7.