202406252115

Status:

Tags: ECG

Ashman phenomenon

first reported in 1947 by Gouaux & Ashman
they showed that the earlier in the cardiac cycle a premature atrial contraction (PAC) occurs, and the longer the preceding cycle is, the more likely that PAC conduction will deviate from the normal pathway and be conducted with aberration
Benign condition
physiological aberrancy of ventricular conduction due to a change in QRS cycle length

• long → short cycle
• esp likely w/ short-long-short cycle
• usually RBBB morphology best seen in V1
  • ∵ Rt bundle has longer refractory period
    can occur in any supraventricular tachyarrhythmia
• most commonly atrial fibrillation
  refractory period of ventricle related to duration of preceding RR interval
  → aberrant conduction if atrial impulse arrives during refractory period

when aberrancy occurs in groups, can resemble non-sustained VT or PVC

Fisch Criteria

• A relatively long cycle immediately ahead of the cycle terminated by the aberrant QRS complex
• RBBB from aberrancy with a normal orientation of the initial QRS vector: concealed propagation of aberration is possible, such that it is possible to have a series of wide QRS supraventricular beats
• Irregular coupling of aberrant QRS complexes
• Absence of a full compensatory pause, as full compensatory pauses favor a ventricular origin.

Treatment: rate control

References