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 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
.

Click here for a more detailed ECG




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.

Click here for a more detailed ECG




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