Classic ECG Findings of Ventricular Tachycardia
1Accident Service, National Hospital Of Sri Lanka, SriLanka
Ventricular tachycardia is a type of wide complex tachycardia (WCT) with QRS duration of more than 120ms with rate of more than 100bpm. 12lead EGC can be inadequate for definitive differentiation of VT from broad complex tachycardia of supraventricular origin. It is important to identify VT and type of VT if possible as treatment choice can be changed depending on the diagnosis.
VT consists of three or more consecutive ventricular ectopic beats at rate more than 100bpm with broad QRS complexes. It can be non-sustained or sustained ventricular tachycardia depending on whether it lasts for less or more than 30seconds. VT can be further classified as Monomorphic ventricular tachycardia and polymorphic ventricular tachycardia.
Features suggestive of ventricular tachycardia are AV dissociation, caption or fusion beats and many others.
Caption beat is a normally conducted sinus beat resulting in narrow QRS complexes and fusion beat results due to simultaneous ventricular depolarization from ectopic as well as normal conduction system.
WCT with Negative or positive concordance of QRS complexes in precordial leads are suggestive of VT. Negative concordance is strongly suggestive but positive concordance is less strongly suggestive of VT as positive concordance can manifest in antidromic AVRT as well.
Considering axis, extreme axis deviation of more negative than -90 degrees or more than +180 degrees is suggestive of VT. QRS duration in RBBB pattern more than 140ms and in LBBB pattern more than 160ms are more suggestive of VT than of supraventricular in origin.
RBBB pattern QRS morphology with monophasic R or qR in V1 and rS in V6 have more probability to be VT. In LBBB pattern QRS complexes with broad initial R wave of more than 40ms in V2 or V2 and Q or QS in V6wave favours VT. Other features are called Brugada’s sign and Josephson’s signs, those are onset of QRS to nadir of S of >100ms and notching near nadir of S wave.
Several algorithms been developed with aim of determining the source of wide complex tachycardia but those may be complex and lacks acceptance, also none of those approaches recommended for Emergency Department.