VT Origin

VT Localizer

Cheat Sheet

Finding Suggests
LBBB VT RV origin
RBBB VT LV origin
Inferior axis Outflow tract or superior origin
LBBB + inferior axis Classic RVOT VT pattern
High MDI Epicardial VT
Structural abnormalities or scar Idiopathic VT less likely

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