Rhythm diagnosis in regular wide complex tachycardia

(Redirected from V Tach vs. SVT)

Assume ventricular tachycardia until proven otherwise



Monomorphic ventricular tachycardia
PSVT at ~180 bpm
Termination of PSVT following adenosine
V-Tach SVT with Aberrancy
Age >50 <35
Cannon A Waves Present Absent
Arterial Pulse Variation No variation
First heart sound Variable Not variable
Fusion Beats Present Absent
AV dissociation Present Absent
QRS >0.14sec <0.14sec
Axis Extreme LAD (< -30) Normal or slightly abnormal
Vagal Maneuvers No response Slows or terminates

QRS morphology

(RBBB-like pattern)

V1 - R or qR

V6 - rS

V1 - rsR'

V6 - R(slurredS)

QRS morphology

(LBBB-like pattern)

V1 or V2 - Broad R wave (>40msec)

V6 - Any Q or QS

V1 - rS or QS

V6 - qRs

Diagnostic Algorithms

  • Only for regular rhythms, if irregular consider a-fib with block
  • Only for treatment decision if patient is stable
  • Assume V-tach until proven otherwise

Brugada Algorithm

  • Absence of an RS complex in all precordial leads?
    • If yes then VT
    • If no then continue
  • RS interval >100ms in any precordial lead? (onset of R wave to deepest part of S wave)
    • If yes then VT
    • If no then continue
  • AV dissociation?
    • If yes then VT
    • If no then continue
  • Morphology criteria for v-tach present in both V1-2 and V6?
    • If yes then VT
    • If no then possibly SVT with aberrant conduction

aVR Algorithm

  • In lead aVR:
  • Presence of an initial R wave?
    • If yes then VT
    • If no then continue
  • Presence of an initial r or q wave >40ms
    • If yes then VT
    • If no then continue
  • Presence of a notch on descending limb of a negative onset, predominantly negative QRS?
    • If yes then VT
    • If no then continue
  • Ventricular activation-velocity ratio (Vi/Vt) ≤1?
    • If yes then VT
    • If no then SVT

Niemann Algorithm[1]

Neimann Algorithm for Regular WCT
  • Combination of the most specific aspects of the above two algorithms

Acronym: CARMAConcordance → aVR →Regular → Morphology →AV dissociation

  • Presence of an initial R wave in aVR? [2][3]
    • If yes then VT
    • If no then continue
  • Is there concordance (monophasic with same polarity) in all of the precordial leads? [4]
    • If yes then VT
      Example of concordance in precordial leads
      Example of disconcordance in precordial leads
    • If no then continue
  • Is there evidence of AV dissociation/Capture beats?
    Example of capture beat
    • If yes then VT
    • If no then continue
  • Is the QRS morphology in V1 and V6 consistent with either LBBB or RBBB? [5][6]
    • If no then VT
    • If yes then SVT with aberrancy

R-Wave Peak Time Method

  • In lead II, if the TIME in (ms) it takes the R wave to go from the isoelectric line to its peak voltage is greater than 50ms, it is VT
  • Positive Likelihood ratio of 34.8

Lesser Known Criteria

  • Josephson's sign --- notching or slurring near the nadir of the S-wave is characteristic of V. Tach
    Josephson's Sign Vtach
  • Rsr' sign --- A taller left R wave in v1-v2 is very specific for VT, as opposed in a RBBB where the second/right R-wave (R') is taller
  • "Northwest" axis deviation -- Negative QRS complex in I, AVF and Positive QRS in AVR

See Also


  1. James Niemann MD FACEP is EM Faculty at Harbor-UCLA Medical Center and prominent resuscitation researcher
  2. Vereckei A et al. New algorithm using only lead aVR for differential diagnosis of wide QRS complex tachy- cardia. Heart Rhythm 2008; 5:89-98
  3. Szelenyi Z, et al. Acad Emerg Med 2013;20:1121- 1130
  4. Brugada P et al. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation 1991;83:1649-1659
  5. Brugada, Circulation; Griffith MJ et al. Lancet 1994;343:386-388
  6. Wellens HJJ et al. Am J Med 1978; 64:27-33


Ross Donaldson