VT and Its Origin by Surface 12 leads ECG : Tips and Tricks

 Tip and Trick of VT Origin by surface EKG 

QRS Axis depends on the direction of spread of depolarization during NSZR and VT

QRS Axis depends on the site of origin of VT.

In a normal ECG the frontal plane QRS axis is between   -30' and +90', with the axis most commonly lying at around 60.

A change in axis of more than 40' to the left or right is probably suggestive of VT during tachycardia .

Lead AVR is situated in the frontal plane at -120' when the axis is normal QRS complex is entirely negative .

Superior axis was defined when the S-wave had a greater amplitude than the R-wave in all inferior leads (leads II, III, aVF) on the 12-lead ECG.

When QRS is positive in lead AVR the tachycardia is originating from apex and moving towards the base of the heart.

VT origin in the apical part of the ventricle has superior axis (to the left of -30').

An inferior axis present when the VT has an origin in the basal area of the ventricle .

Most commonly, VT features a left axis deviation.

If the origin is closer to the septum, RAD will be present.

Recently, some reports have described VAs with superior axis (SupAx-VA) arising from sites such as the mitral annulus,8 tricuspid annulus,9 posterior papillary muscle.

 

This review summarizes common forms of idiopathic ventricular tachycardias that the general cardiologist should know. Table 1

ECG recognition – RVOT VT is associated with a characteristic ECG morphology of LBBB with inferior axis . Anterior sites in the RVOT show a dominant Q-wave or a qR complex in lead I and a QS complex in aVL. Pacing at the posterior sites produce a dominant R-wave in lead I, QS  or R-wave in aVL and an early precordial transition (R/S = 1 by V3). (1)

 

LVOT VT is suggested by LBBB morphology with inferior axis with small R-waves in V1 and early precordial transition (R/S = 1 by V2 or V3) or RBBB morphology with inferior axis and presence of S-wave in V6.

Aortic sinus cusp origin is sometimes difficult to differentiate from RVOT VT because both are so close to each other. Coronary cusp origin it has to be though when we fail an ablation in the RVOT, ECG shows a LBBB inferior axis morphology with taller monophasic R-waves in inferior leads and an early precordial R-wave transition by V2-V3. Ouyang et al. evaluated the ECG differences between RVOT/aortic sinus cusp VT origin. They found that a broader R-wave duration and a taller R/S wave amplitude in V1-V2 favored VT arising from the aortic cusp.

 

References

 

Twelve-Lead ECG of Ventricular Tachycardia in Structural Heart Disease https://www.ahajournals.org/doi/pdf/10.1161/CIRCEP.115.002847?download=true

How to recognise and manage idiopathic ventricular tachycardia : An article from the e-Journal of Cardiology Practice https://www.escardio.org/Journals/E-Journal-of-Cardiology-Practice/Volume-8/How-to-recognise-and-manage-idiopathic-ventricular-tachycardia

Ventricular arrhythmias with superior axis originating from the left ventricular septum: electrocardiographic characteristics predicting successful ablation and insights into their mechanism-observations from a small series of patients https://academic.oup.com/europace/article/17/10/1587/2466145