VT Origin

EKG Lead & Coronary Map Interactive lead orientation, coronary territories & vessel correlates

Lead orientation

aVR aVL I II aVF III RA LA RV LV V1 V2 V3 V4 V5 V6
EKG lead orientation

Coronary territories

Coronary anatomy select a vessel
RV LV LAD D1 LCx RCA PDA PDA = posterior
12-lead territory map
Posterior leads same horizontal plane as V6
Coronary territory map

VT Localizer

Stepwise EKG localization of VT origin

1

Bundle Morphology

What is the bundle pattern?
Use the predominant QRS morphology in V1. LBBB is predominantly negative in V1. RBBB is predominantly positive in V1.
2

Frontal Plane Axis

Choose whether the QRS is predominantly positive or negative in each limb lead.
Select Lead I and aVF to determine the axis quadrant.
3

Precordial Transition

Where is the R-wave transition?
The transition is where the R wave becomes larger than the S wave, meaning the QRS becomes predominantly positive.
4

V1 Morphology

What does the QRS look like in V1?
Choose the pattern that most closely resembles the ventricular QRS.
How to read these patterns
QS
Entire QRS is negative with no initial R wave.
rS
Small initial R followed by a larger negative S wave.
Monophasic R
One dominant positive R wave without a major S wave.
qR
Small initial negative q wave followed by a dominant R wave.
rsR′ / RSR′
Positive-negative-positive pattern with a terminal R′.
5

Additional Limb-Lead Clues

aVR morphology
Note the predominant polarity and whether an initial R wave is present.
aVL morphology
Record the predominant QRS polarity or a clear initial q wave.
6

Structural Heart Disease

Select any known substrate. These findings change how strongly an apparently idiopathic EKG pattern should be interpreted.
Quick Localization Cheat Sheet
Finding What it suggests
LBBB morphology Favors a right ventricular or septal site of origin.
RBBB morphology Favors a left ventricular site of origin.
Inferior axis Activation is directed inferiorly, suggesting a superior origin such as the ventricular outflow tracts.
LBBB + inferior axis Classic morphology of RVOT ventricular arrhythmia.
Early precordial transition In an outflow-tract pattern, favors a more leftward source such as LVOT or aortic cusp origin.
Late precordial transition In an outflow-tract pattern, favors RVOT origin.
RBBB + superior axis Consider LV inferoseptal origin or posterior fascicular VT, particularly without structural heart disease.
Known myocardial scar Raises concern for scar-related VT even when the surface morphology resembles an idiopathic focus.

RV or LV

LBBB morphology

  • Mostly negative in V1
  • Usually means VT starts in the RV
  • Reason: activation moves right to left
  • Examples
    • RVOT VT
    • Other RV free wall VT
    • ARVC-related VT

RBBB morphology

  • Mostly positive in V1
  • Usually means VT starts in the LV
  • Reason: activation moves left to right
  • Examples
    • LV scar VT
    • Fascicular VT
    • LV summit / LVOT VT

Axis

Inferior axis

  • Positive in II, III, aVF
  • Impulse is traveling downward
  • Suggests a superior origin
  • Examples
    • RVOT VT
    • LVOT VT

Superior axis

  • Negative in II, III, aVF
  • Impulse is traveling upward
  • Suggests an inferior origin
  • Examples
    • Inferior scar VT
    • Apical or inferior ventricular origin

Precordial Transition

Late Transition

  • More rightward / later transition can support RVOT origin
  • Transition ≥ V5

Early Transition

  • Earlier transition can support LVOT origin
  • Transition in V1-V3

Maximum Deflection Index (MDI)

MDI helps predict epicardial vs endocardial origin

  • MDI = time from QRS onset to maximum deflection / total QRS duration
  • Helps plan epicardial (riskier) vs endocardial ablation
  • Helps determine what disease process may be causing scar
    • Pick a precordial lead with a clear VT complex
    • Mark QRS onset
    • Mark the point of maximum positive or negative deflection
    • Measure: onset to maximum deflection and total QRS duration
    • Divide the first by the second
  • Interpretation
    • MDI < 0.55: endocardial origin more likely
    • MDI ≥ 0.55 to 0.60: epicardial origin more likely

Maximum Deflection Index Calculator

References

  1. Yamada, T., McElderry, H. T., Doppalapudi, H., Okada, T., Murakami, Y., Yoshida, Y., Yoshida, N., Inden, Y., Murohara, T., Plumb, V. J., Kay, G. N., & Epstein, A. E. (2008). Idiopathic ventricular arrhythmias originating from the aortic root: Prevalence, electrocardiographic and electrophysiologic characteristics, and results of radiofrequency catheter ablation. Journal of the American College of Cardiology, 52(2), 139–147. https://doi.org/10.1016/j.jacc.2008.03.041
  2. Betensky, B. P., Park, R. E., Marchlinski, F. E., Hutchinson, M. D., Garcia, F. C., Dixit, S., Callans, D. J., Cooper, J. M., Bala, R., Lin, D., Riley, M. P., Gerstenfeld, E. P., & Dixit, S. (2011). The V2 transition ratio: A new electrocardiographic criterion for distinguishing left from right ventricular outflow tract tachycardia origin. Journal of the American College of Cardiology, 57(22), 2255–2262. https://doi.org/10.1016/j.jacc.2011.01.035
  3. Daniels, D. V., Lu, Y. Y., Morton, J. B., Santucci, P. A., Akar, J. G., Green, A., Wilber, D. J., & Ouyang, F. (2006). Idiopathic epicardial left ventricular tachycardia originating remote from the sinus of Valsalva: Electrocardiographic characteristics, catheter ablation, and identification from the 12-lead electrocardiogram. Circulation, 113(13), 1659–1666. https://doi.org/10.1161/CIRCULATIONAHA.105.611640
  4. Berruezo, A., Mont, L., Nava, S., Chueca, E., Bartholomay, E., & Brugada, J. (2004). Electrocardiographic recognition of the epicardial origin of ventricular tachycardias. Circulation, 109(15), 1842–1847. https://doi.org/10.1161/01.CIR.0000125525.04081.4B
  5. Yoshida, N., Inden, Y., Uchikawa, T., Kamiya, H., Kitamura, K., Shimano, M., Tsuji, Y., Hirai, M., Murohara, T., & Yamada, T. (2011). Novel transitional zone index allows more accurate differentiation between idiopathic right ventricular outflow tract and aortic sinus cusp ventricular arrhythmias. Heart Rhythm, 8(3), 349–356. https://doi.org/10.1016/j.hrthm.2010.11.023
  6. Cronin, E. M., Bogun, F. M., Maury, P., Peichl, P., Chen, M., Namboodiri, N., Aguinaga, L., Leite, L. R., Al-Khatib, S. M., Anter, E., Berruezo, A., Callans, D. J., Chung, M. K., Cuculich, P., d’Avila, A., Deal, B. J., Della Bella, P., Deneke, T., Dickfeld, T. M., ... Zeppenfeld, K. (2020). 2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias. Heart Rhythm, 17(1), e2–e154. https://doi.org/10.1016/j.hrthm.2019.03.002