Ashman phenomenon

Presentation

Ashman beats are described as wide complex QRS complexes that follow a short R-R interval preceded by a long R-R interval. This short QRS complex typically has a right bundle branch block morphology and represents an aberrantly conducted complex that originates above the AV node, rather than a complex that originates in either the right or left ventricle.

Cause

It occurs because the duration of the refractory period of the myocardium is proportional to the R-R interval of the preceding cycle. A short R-R interval is associated with a shorter duration of action potential and vice versa. A long R-R cycle will prolong the ensuing refractory period, and if a shorter cycle follows, the beat terminating the cycle is likely to be conducted aberrantly. Because the refractory period of the right bundle branch is longer than the left, the right bundle will still be in the refractory period when the supraventricular impulse reaches the His-Purkinje system, resulting in a complex with right bundle branch block morphology.

Prognosis

Clinically, it is often asymptomatic by itself and considered benign in nature.

References

References

1. (2004). "The Ashman phenomenon". J La State Med Soc.
2. Gouaux, JL. (Sep 1947). "Auricular fibrillation with aberration simulating ventricular paroxysmal tachycardia.". American Heart Journal.
3. "Review #1".