Definition

  Aberration (aberrant conduction) is conduction of the supraventricular impulse to the ventricles in a markedly different manner from the usual conduction .

  Aberration is seen as bundle branch block pattern (wide QRS complex).

  Since refractory period of the right bundle branch is longer than that of the left bundle branch, aberration occurs as right bundle branch block in 80% of the cases.

  In patients with abnormal hearts, aberration may be also seen as left bundle branch block.

 
Any type of supraventricular rhythm may show aberrancy: sinus rhythm, nodal rhythm, atrial premature beat, supraventricular tachycardias, atrial fibrillation, atrial flutter with variable block.

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




Pathophysiology

  A sudden change in the length of the previous cardiac cycle results in a refractory right or left bundle branch.

 
Refractoriness in any bundle branch does not allow the supraventricular impulse to propagate in that branch. This results in bundle branch block and hence "wide QRS complex".



Clinical significance

  Identification of the wide QRS complex as aberration helps to exclude the diagnosis of VPC.



Rate-dependent aberration and its restitution

  As the heart rate increases, the refractory period of the His-Purkinje system shortens.

  This helps to preserve normal conduction.

  Failure of the action potential of the bundle branches to shorten results in acceleration dependent bundle branch block.

  Paradoxical lengthening of the action potential in response to heart rate increase may also result in acceleration dependent bundle branch block.

  Conversely, the refractory period increases as the heart rate decreases.

  When heart rate further increases, the acceleration dependent aberration may sometimes disappear (
restitution). This may be due to greater shortening of the effective refractory period of the bundle branches than that of the AV node.



References

  Josephson ME: Intraventricular conduction disturbances. In Josephson ME, editor: Clinical cardiac electrophysiology, ed 4, Philadelphia, 2008, Lippincott Williams & Wilkins, pp 114-144.

  Fisch C, Knoebel S: Wolff-Parkinson-White syndrome. In Fisch C, Knoebel S, editors: Electrocardiography of clinical arrhythmias, Armonk, NY, 2000, Futura, pp 293-314.

  Clinical Arrhythmology and Electrophysiology. A Companion to Braunwald’s Heart Disease. SECOND EDITION. 2012 Elsevier Saunders. pp 194-211.





ECG 1a. The last beat in the above ECG
is conducted aberrantly and is due to an atrial premature contraction (APC) . One of
the reasons that this APC was conducted aberrantly is that
cardiac cyle before the beat preceeding the APC is a long cycle .
A short cycle coming after a long cycle eases aberrancy.

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ECG 1b. Above is the magnified view of last part of the ECG 1a. The
T wave , the Atrial Premature
Contraction
( APC ) deforming it and the aberrantly conducted QRS complex is seen.





ECG 2. Rate dependent aberration. In the upper tracing, it is clearly seen that aberration occurs when heart rate increases.
In the lower tracing aberration, when heart rate slows down the aberration with wide QRS complexes disappear and narrow
QRS complexes reappear.

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ECG 3. Rate dependent aberration in another patient.
The first 3 beats from the left are conducted with aberration as left
bundle branch block. As the heart rate decreases, aberration disappears and P waves are conducted normally (as narrow
QRS complexes).

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ECG 4. Rate dependent aberration in another patient. When the heart rate (HR) decreases, aberration disappears and narrow
QRS complexes (normal conduction) appear. The numbers on the upper row show instantenous heart rate while the numbers
below them show the corresponding RR intervals in miliseconds.

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ECG 5a. The ECG above belongs to a 25 years-old puerpera (one day after childbirth).
P waves with at least 3 different
shapes
show wandering atrial pacemaker. When P waves originate from various atrial foci, their shapes also vary.

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ECG 5b. Her ECG next day shows atrial bigeminy.
Every P wave originating from the sinus node is followed by a premature
P wave originating from an ectopic focus
in the atria.
The premature P wave is negative in the above ECG, suggesting a low atrial focus.
However, all atrial premature beats should NOT necessarily be negative.
Negativity of the P wave is related to its focus, but not to its prematurity.


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ECG 5c. A few hours later, her ECG shows that atrial premature contractions are now coming earlier and being conducted with
aberration.
Some P waves are conducted normally to the ventricles . Some premature P waves are conducted with left
anterior fascicular block (LAFB)
while some others are conducted with left bundle branch block (LBBB) morphology.

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ECG 6a. The ECG above is from a 64 years-old man. The basic rhythm is sinus with a heart rate of 60/minute.
QRS complexes are narrow. A VPC is seen in precordial leads.

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ECG 6b. A few minutes later, his second ECG was recorded.
Now, the heart rate is 75/minute and the QRS complexes are widened.
This QRS widening in the form of RBBB is called acceleration dependent aberration.

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ECG 7a. The ECG above belongs to a middle-aged woman. She was diagnosed as normal coronary arteries and dilated
cardiomyopathy. The basic rhythm is
sinus rhythm with aberrant conduction as left bundle branch block (LBBB) .
The
Ventricular Premature Systole (VPS) is followed by compensatory pause. As the instantaneous heart rate during the
compensatory pause was slow enough,
aberration disappeared and the sinus beat was conducted normally to the ventricles as
a narrow QRS complex
.

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ECG 7b. The ECG was recorded again.
VPS was observed among sinus beats conducted with LBBB type aberration .
When heart rate was slow enough during the compensatory pause,
the aberration disappeared and the sinus beat was normally
conducted to the ventricles as a narrow QRS complex
.

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ECG 7c. The 3-lead Holter recording of the same patient showed
VPS and normal conduction of the sinus beat following the
compensatory pause.
This Holter recording showed that the normal conduction (without aberration) was related to the
instantaneous heart rate . When the instantaneous heart rate was 69/minute or below the aberration disappeared and
the sinus beat was
conducted normally to the ventricles.

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ECG 7d. Another instance from the 3-lead Holter recording of the same patient shows how important the instantaneous
heart rate is for aberration.
When instantaneous heart rate is 69/minute or below the sinus beat following the compensatory
pause of the
VPS is conducted normally (without aberration) . When instantaneous heart rate is above 69/minute aberration
reappears.

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ECG 7e.
The aberrant conduction persists when the instantaneous heart rate of the compensatory pause of the VPS
is above 69/minute

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ECG 7f.
LBBB type aberrant conduction occurs when the instantaneous heart rate is above >69/minute or below 104/minute.

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ECG 7g.
When the instantaneous heart rate is 104/minute or above the aberration disappears and conduction normalizes
(RESTITUTION)
. When heart rate comes below 104/minute aberration reappears again.

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ECG 8a. The ECG above belongs to a 48 year-old man. It was recorded 3 weeks after his Bentall surgery.
ECHOcardiography showed left ventricular hypertrophy.
The above ECG shows frequent
VPCs with acceleration dependent aberration.
If
compensatory pause following the VPC is not long enough, then acceleration dependent aberration developes and
QRS complex widens
. If compensatory pause following the VPC is long enough, then
acceleration dependent aberration does not develope and QRS complex following the VPC does not widen.

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ECG 8b. The ECG above belongs to the same man. It was recorded 70 minutes before the ECG 8a.
This ECG also shows frequent
VPCs.
However, if
compensatory pause following the VPC is not long enough, then
acceleration dependent aberration developes and QRS complex widens.

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ECG 9. The ECG above belongs to a 57 years-old obese man.
He is under Amlodipin therapy for chronic systemic arterial hypertension.
ECHOcardiography showed normal left ventricular systolic function with normal cardiac dimensions.
Basic rhythm is sinus with right bundle branch block (RBBB) morphology.
There are frequent atrial premature beats deforming the preceding T waves.
The atrial premature beats are conducted to the ventricles with aberration resulting in bizarre QRS complexes.

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ECG 10. During atrial fibrillation, a wide QRS complex may not be due to aberrancy or a VPC.
The ECG above belongs to a 74 years-old woman and the basic rhythm is atrial fibrillation.
She also has a VVI-pacemaker.
The pacemaker spike is not easy to notice, at first glance.
The QRS complex is widened not due to aberrancy or a VPC but due to stimulation from ventricular pacemaker.

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ECG 11.
Aberration during supraventricular tachycardia is seen above.
This ECG belongs to a 25 years-old woman.
10 mg intravenous Adenosine converted her rhythm to sinus.

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ECG 12. The above ECG belongs to a 13 years-old boy with frequent
atrial premature beats.
Atrial premature beats deform the preceding T waves.
Some atrial premature beats are conducted with
aberration resulting in wide QRS complexes.
These wide QRS complexes are not ventricular premature contractions.
There are two reasons for this: T waves preceding
the wide QRS complexes are different
(due to the deforming effect of the atrial premature beat); also there is no compensatory pause.
The seemingly
sinus arrest is in fact due to a blocked atrial premature beat.
There is no sinus arrest.

Arm electrodes were inadvertently reversed in this ECG

Prof. Dr. Nazlıhan Günal has donated the above ECG to our website.

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ECG 13. The above ECG shows
aberration during supraventricular tachycardia.
Aberrantly conducted beats are not premature. Aberrant conduction resulted in wide QRS complexes.

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ECG 14. The ECG above belongs to a 76 years-old woman with coronary artery disease and
left ventricular systolic dysfunction (LVEF 35%).
Atrial rate is above 100/minute: atrial tachycardia.
Of every 3 P waves, only one of them is conducted to the ventricles (high degree AV block)
with prolonged PR interval and aberration.
In this tracing, only
one P wave is conducted with a normal PR interval and without aberration.

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ECG 15. The ECG above belongs to a 12 years-old boy with the complaint of palpitation.
It was recorded just before his electrophysiological study and successful ablation.
Ectopic atrial tachycardia with intermittent aberration is seen.

Pediatric Cardiologist Prof. Dr. Tevfik Karagoz has donated the above ECG to our website.

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