Ashman Phenomenon Workup

Updated: Dec 22, 2020
  • Author: Roger Freedman, MD; Chief Editor: Jeffrey N Rottman, MD  more...
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Workup

Approach Considerations

Electrocardiography

Ashman phenomenon is diagnosed using a surface electrocardiogram (ECG) (all 12 leads are best). In difficult cases, electrophysiological studies are required to establish whether the arrhythmia is of supraventricular or ventricular origin. [2]  See the image below.

Ashman Phenomenon. Ashman phenomenon illustrated o Ashman Phenomenon. Ashman phenomenon illustrated on electrocardiograpm by the 12th and 15th beats, which follow a premature ventricular complex and long R-R cycle, respectively. The underlying rhythm is atrial fibrillation.

Fisch criteria for the diagnosis of Ashman phenomenon are as follows [2, 6] :

  • A relatively long cycle immediately preceding the cycle terminated by the aberrant QRS complex: A short-long-short interval is even more likely to initiate aberration. Aberration can be left or right bundle branch block (LBBB, RBBB); both patterns may be observed in the same patient.

  • RBBB-form aberrancy with normal orientation of the initial QRS vector: Concealed perpetuation of aberration is possible, such that a series of wide QRS supraventricular beats is possible.

  • Irregular coupling of aberrant QRS complexes

  • Lack of a fully compensatory pause (never seen in atrial fibrillation)

QRS morphology is the most helpful clue in differentiating between a supraventricular and ventricular origin of wide QRS complexes. The morphologic features that favor ventricular origin of wide complexes include the following:

  • LBBB morphology with slurred or notched downstroke in leads V1 or V2

  • RBBB morphology with monophasic R, biphasic QRS, or rSR' (ie, "rabbit ear") pattern in V1

  • QS pattern in V6

  • QRS duration longer than 140 milliseconds in RBBB morphology and QRS duration longer than 160 milliseconds in LBBB morphology

  • R-to-S interval longer than 100 milliseconds in a precordial lead

  • Marked left axis (between -90° and 180°)

Several studies by Marriott et al [7]  and Gulamhusein et al [8]  have analyzed His electrogram findings with simultaneous surface ECG findings and found low sensitivity and specificity of Ashman phenomenon for helping diagnose aberrancy versus ventricular rhythm.

Aberration may also be a sign of intermittent ventricular preexcitation via an accessory pathway, as may occur with Wolff-Parkinson-White syndrome.