Overview

• The phenomenon was first reported in 1947 by Gouaux and Ashman; they noted that when a relatively long cycle was followed by a relatively short cycle in atrial fibrillation, the beat terminating the short cycle often had a right bundle branch block (RBBB) morphology (i.e. Ashman beat)
• Aberrant intraventricular conduction of an impulse that completes a short cardiac cycle following a long cycle due to the long cycle resulting in delay of repolarization
• Occurs when a relatively long RR interval is followed by a short RR interval and terminated by aberrant ventricular conduction (Ashman beat) that typically has a RBBB morphology (i.e. long RR interval -> short RR interval -> Ashman beat)
• Most commonly associated with atrial fibrillation, but it may also be seen with other supraventricular arrhythmias
• Most patients are asymptomatic and do not require specific treatment
• Also referred to as: Ashman beat, Ashman aberrancy

ECG Features

• Relatively long cycle immediately preceding the cycle terminated by the aberrant QRS complex
• RBBB-form aberrancy with normal orientation of the initial QRS vector (wide QRS supraventricular beats are possible)
• Irregular coupling of aberrant QRS complexes
• Short-long-short RR interval is even more likely to initiate aberration
• Lack of a fully compensatory pause

Mechanism

• The refractory period of the His-Purkinje system is proportional to the RR interval of the preceding beat.
• When there is a long RR interval between two beats, a relatively long refractory period will follow.
• If a short RR interval (e.g. premature supraventricular impulse) follows a long RR interval while the His-Purkinje system is still refractory, then the conducted beat will conduct aberrantly and have a different morphology.
• Because the refractory period of the right bundle branch is slightly longer than the left bundle branch, the aberrantly conducted beat will typically display a RBBB morphology.

ECG Example
Patient: 75-year-old male with hypertension

Interpretation: Atrial fibrillation with rapid ventricular response and aberrantly conducted complexes (Ashman phenomenon)
– Ventricular rate: 159 BPM
– PR interval: **
– QRS duration: 96 ms
– QT/QTc interval: 288/468 ms
– P-R-T axes: -1 +24 -12

References

• Gouaux JL. Ashman R. Auricular fibrillation with aberration simulating ventricular paroxysmal tachycardia. American Heart Journal. 1947; 34(3): 366-73. [PMID: 20262631]
• Fisch C. Electrocardiography of arrhythmias: from deductive analysis to laboratory confirmation–twenty-five years of progress. J Am Coll Cardiol. 1983;1(1):306-16. [PMID: 6826940]
• Alraies MC, Eisa N, Alraiyes AH, Shaheen K. The long and short of it: Ashman’s phenomenon. Am J Med. 2013 Nov;126(11):962-3. [PMID: 24050488]
• Lakusic N, Mahovic D, Slivnjak V. Ashman phenomenon: an often unrecognized entity in daily clinical practice. Acta Clin Croat 2010;49:99–100. [PMID: 20635592]