Ashman Phenomenon Differential Diagnoses

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

Understanding Ashman phenomenon is useful in differentiating wide complex arrhythmias of ventricular origin from supraventricular arrhythmias with aberrancy, because the prognosis and treatment of these conditions are different. [1, 2]

A supraventricular impulse with aberrant conduction is confused with a premature ventricular contraction (PVC), and a series of consecutive aberrantly conducted supraventricular impulses may appear to be ventricular tachycardia.

Intermittent ventricular preexcitation, as in Wolf-Parkinson-White syndrome, should also be considered in the differential diagnosis of Ashman phenomenon.

It is important to diagnose and appropriately treat disease entities associated with Ashman phenomenon as well as to diagnose ventricular tachycardia.

Fisch criteria

The Fisch criteria for diagnosing Ashman phenomenon is as follows [2, 6] :

  • A relatively long cycle immediately ahead of the cycle terminated by the aberrant QRS complex: A short-long-short interval is particularly likely to initiate aberration, which could be either left or right bundle branch block (LBBB, RBBB) or both. Both patterns may be occur in the same patient.
  • RBBB from aberrancy with a normal orientation of the initial QRS vector: oncealed propagation of aberration is possible, such that there is a likelihood of a series of wide QRS supraventricular beats.
  • Irregular coupling of aberrant QRS complexes
  • Absence of a full compensatory pause

Differential Diagnoses