Ashman Phenomenon

  Ashman phenomenon is a kind of aberrant conduction.

  If aberration occurs after long-short cycle, it is called as Ashman phenomenon.

  Ashman phenomenon is most frequently observed in patients with
atrial fibrillation.

      It may also be observed in situations
where long and short RR intervals follow each other

      (multifocal atrial tachycardia, etc.).

  The refractory period in bundle branches is directly related to the RR interval of the preceeding beat.

  After a long RR interval, the refractory period of bundle branches will be prolonged.

     
If a short RR interval follows a long RR interval, then the early coming supraventricular stimulus may

      find one of the bundle branchces (either right or left) in a refractory state and may be

      conducted aberrantly.

  The refractory period of the right bundle branch is longer than that of the left bundle branch.

      Therefore the supraventricular impulse is usually conducted as right bundle branch block.

  Sometimes, Ashman phenomenon may persist for a few consecutive beats.

  This phenomenon was first described in 1947 by Dr. Richard Ashman.




How to differentiate an aberrantly conducted Ashman beat from a VPC during atrial fibrillation

  Ashman beats

      - have variable coupling intervals

      - show long-short cycle sequence


 
VPCs

      - have fixed coupling intervals

      - may show long and identical R-R cycles after the aberrant beats.

      - have QRS morphologies which do not resemble RBBB or LBBB.

      - do not show long-short cycle sequence.




Clinical importance

  Has no clinical importance. Does not cause a life threatening arhhythmia.

  The reader of the ECG should know that the aberrantly conducted impulse resulting in a

      wide QRS complex does not originate from the ventricles.




Reference

  Turk Aritmi, Pacemaker ve Elektrofizyoloji Dergisi 2008;6(2):87-96.





ECG 1a.
Long RR interval followed by a short RR interval is conducted aberrantly and resulted in wide QRS complexes in the
form of right bundle branch block
. The rhyhtm tracing at the bottom of the ECG shows that only the longest RR intervals
followed by short cycles resulted in aberration .

Click here for a more detailed ECG




ECG 1b. A second ECG was recorded immediately which showed
long RR interval followed by a short RR interval resulting in
aberration and
wide QRS complex in the form of right bundle branch block .

Click here for a more detailed ECG





ECG 2. Ashman phenomenonen from another patient with atrial fibrillation:
Long RR interval is followed by a short RR interval
which resulted in aberrantly conducted beats (as wide QRS complexes in the form of right bundle branch block ).
As seen in the bottom rhythm tracing
only the short cycle beats following the longest RR intervals are aberrantly conducted .


Click here for a more detailed ECG





ECG 3. Ashman phenomenon in another patient:
Long RR interval is followed by short RR intervals which in turn is followed
by
aberrantly conducted beats ( wide QRS complexes in the form of right bundle branch block .
Ashman phenomenon may persist for a few
consecutive beats .

Click here for a more detailed ECG





ECG 4. Ashman phenomenon in a patient with multifocal atrial tachycardia.
There are
P waves with more than 3 different shapes .
Aberrantly conducted beats
may be seen consecutively.

Click here for a more detailed ECG





ECG 5a. Ashman phenomenon is not specific to atrial fibrillation.
It may be observed in rhythms where long and short RR intervals follow each other.
Above is a 3-channel ECG Holter tracing from a middle-aged man.
The basic rhythm is sinus tachycardia with frequent APCs. Sweep speed is 25mm/sec.

The APC in the mid portion
is conducted normally to the ventricles producing a narrow QRS.
The next APC is blocked
resulting in a pause due to failure of conduction to the ventricles .
The following APC
is conducted aberrantly to the ventricles resulting in a wide QRS complex .
After a long RR interval, the refractory period of bundle branches will be prolonged.
If a short RR interval follows a long RR interval, then the early coming supraventricular stimulus may find
one of the bundle branchces (either right or left) in a refractory state and may be conducted aberrantly.

Click here for a more detailed ECG




ECG 5b. Above is the 50 mm/sec display of the same Holter tracing. Details are seen better.

Click here for a more detailed ECG





ECG 6a. The 6-channel precordial rhythm tracing above is from a 53 years-old man with mitral valve prosthesis and
new-onset atrial fibrillation. ECHOcardiography showed normal left ventricular systolic function.
The above tracing shows left bundle branch block (LBBB) type aberration which follows a long cycle.

Click here for a more detailed ECG




ECG 6b. Above is another tracing from the same patient and was recorded a few seconds later.
Again, left bundle branch block (LBBB) type aberration follows a long cycle.

Click here for a more detailed ECG




ECG 6c. A few seconds later, right bundle branch block (RBBB) type aberration is seen in the same patient.

Click here for a more detailed ECG