Ashman phenomenon describes an aberrant ventricular conduction, usually of RBBB morphology, which follows a short R-R interval and preceding relatively prolonged R-R interval

  • Typically seen with atrial fibrillation but can also occur with other supraventricular arrhythmias
  • Clinically on its own is asymptomatic and does not require any specific treatment
ECG Ashman Phenomenon 5

Ashman phenomenon. Occurs when a long RR interval is followed by a short RR interval and terminated by the aberrant QRS complex

History of the Ashman Phenomenon

1947 – Gouaux and Ashman reported that in atrial fibrillation, when a relatively long cycle was followed by a relatively short cycle, the beat with a short cycle often has Right Bundle Branch Block morphology.

1983 – Fisch criteria for the diagnosis of Ashman phenomenon

  1. Relatively long cycle immediately preceding the cycle terminated by the aberrant QRS complex;
  2. RBBB-form aberrancy with normal orientation of the initial QRS vector, a series of wide QRS supraventricular beats is possible;
  3. Irregular coupling of aberrant QRS complexes;
  4. A short-long-short RR interval is even more likely to initiate aberration; and 
  5. Lack of fully compensatory pause.


The refractory period of the His-Purkinje system is proportional to the RR interval of the preceding beat. So, when two beats are separated by a long RR interval, the subsequent refractory period will be relatively long. 

If a premature supraventricular stimulus (short RR interval) follows a long RR interval whilst the His-Purkinje system is still refractory, then the conducted beat will appear abnormal. As the refractory period of the right bundle is slightly longer than the left, the aberrantly-conducted beat typically demonstrates a right bundle branch (RBBB) morphology.

ECG Ashman aberrancy 4
ECG Ashman aberrancy 5

Alternate Names
  • Ashman beat
  • Ashman aberrancy



the names behind the name

BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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