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Cardiology > Arrhythmias
Ashman Phenomenon
Article Last Updated: Mar 23, 2006
AUTHOR AND EDITOR INFORMATION
Section 1 of 9  
Author: Ram C Sharma, MD, MRCP, Assistant Professor of Medicine, Division of Cardiology, Department of Internal Medicine, University of Utah Health Science Center
Ram C Sharma is a member of the following medical societies: American College of Physicians and American Heart Association
Coauthor(s):
Roger Freedman, MD, Director of Arrhythmia Service, Director of Electrophysiology Fellowship, Professor, Department of Internal Medicine, Division of Cardiology, University of Utah School of Medicine
Editors: Russell F Kelly, MD, Program Director, Assistant Professor, Department of Internal Medicine, Division of Cardiology, Cook County Hospital, Rush Medical College; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Brian Olshansky, MD, Professor of Medicine, Department of Internal Medicine, University of Iowa College of Medicine; Amer Suleman, MD, Consultant in Electrophysiology and Cardiovascular Medicine, Department of Internal Medicine, Division of Cardiology, Medical City Dallas Hospital; Leonard Ganz, MD, Associate Professor of Medicine, Temple University School of Medicine; Cardiac Electrophysiologist, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Cent, West Penn Hospital
Author and Editor Disclosure
Synonyms and related keywords:
aberrant ventricular conduction, aberrant conduction, right bundle-branch block morphology, RBBB morphology, intraventricular conduction abnormality, premature ventricular complexes, PVCs
Background
Ashman phenomenon is an aberrant ventricular conduction due to a change in QRS cycle length. In 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 (RBBB) morphology. This causes diagnostic confusion with premature ventricular complexes (PVCs). If a sudden lengthening of the QRS cycle occurs, the subsequent impulse with a normal or shorter cycle length may be conducted with aberrancy.
Pathophysiology
Ashman phenomenon is an intraventricular conduction abnormality caused by a change in the heart rate. This is dependent on the effects of rate on the electrophysiological properties of the heart and can be modulated by metabolic and electrolyte abnormalities and the effects of drugs.
The aberrant conduction depends on the relative refractory period of the conduction tissues. The refractory period depends on the heart rate. Action potential duration (ie, refractory period) changes with the R-R interval of the preceding cycle; shorter duration of action potential is associated with a short R-R interval and prolonged duration of action potential is associated with a long R-R interval. A longer cycle lengthens the ensuing refractory period, and, if a shorter cycle follows, the beat ending it is likely to be conducted with aberrancy.
Aberrant conduction results when a supraventricular impulse reaches the His-Purkinje system while one of its branches is still in the relative or absolute refractory period. This results in slow or blocked conduction through this bundle branch and delayed depolarization through the ventricular muscles, causing a bundle-branch block configuration (ie, wide QRS complex) on the surface ECG, in the absence of bundle-branch pathology. A RBBB pattern is more common than a left bundle-branch block (LBBB) pattern because of the longer refractory period of the right bundle branch.
Several studies have questioned the sensitivity and specificity of the long-short cycle sequence. Aberrant conduction with a short-long cycle sequence has also been documented.
Frequency
United States
No geographic variations occur. Ashman phenomenon is related to the underlying pathology and is a common ECG finding in clinical practice.
History
- The diagnosis of Ashman phenomenon is made using ECG evaluation findings. Patients may be asymptomatic or may have symptoms of the underlying cardiac condition.
- Ashman phenomenon, per se, causes no symptoms. Symptoms, if present, are related to the premature complexes and are not related to whether the complexes are conducted aberrantly.
Physical
- No specific physical examination findings are described for Ashman phenomenon.
- Pulse findings may include an irregular pulse, tachycardia, and/or pulse deficit in atrial fibrillation.
Causes
- Conditions causing an altered duration of the refractory period of the bundle branch or the ventricular tissue cause Ashman phenomenon. These conditions are commonly observed in (1) atrial fibrillation, (2) atrial tachycardia, and (3) atrial ectopy.
Ventricular Premature Complexes
Ventricular Tachycardia
Other Problems to be Considered
Understanding Ashman phenomenon is useful in differentiating wide complex arrhythmias of ventricular origin from supraventricular arrhythmias with aberrancy because the prognosis and treatment of these conditions are different.
A supraventricular impulse with aberrant conduction is confused with a PVC, and a series of consecutive aberrantly conducted supraventricular impulses may appear to be ventricular tachycardia.
Intermittent ventricular preexcitation, as in Wolf-Parkinson-White syndrome, should also be considered in the differential diagnosis of Ashman phenomenon.
Other Tests
- Ashman phenomenon is diagnosed using a surface ECG (all 12 leads are best). In difficult cases, electrophysiological studies are required to establish whether the arrhythmia is of supraventricular or ventricular origin.
- Fisch criteria for the diagnosis of Ashman phenomenon are as follows:
- A relatively long cycle immediately preceding the cycle terminated by the aberrant QRS complex: A short-long-short interval is even more likely to initiate aberration. Aberration can be LBBB and RBBB, even in the same patient.
- RBBB-form aberrancy with normal orientation of the initial QRS vector: Concealed perpetuation of aberration is possible, such that a series of wide QRS supraventricular beats is possible.
- Irregular coupling of aberrant QRS complexes
- Lack of a fully compensatory pause (never seen in atrial fibrillation)
- QRS morphology is the most helpful clue in differentiating between a supraventricular and ventricular origin of wide QRS complexes. The morphologic features that favor ventricular origin of wide complexes include the following:
- LBBB morphology with slurred or notched downstroke in leads V1 or V2
- RBBB morphology with monophasic R, biphasic QRS, or rSR' (ie, "rabbit ear") pattern in V1
- QS pattern in V6
- QRS duration longer than 140 milliseconds in RBBB morphology and QRS duration longer than 160 milliseconds in LBBB morphology
- R-to-S interval longer than 100 milliseconds in a precordial lead
- Marked left axis (between -90° and 180°)
- Several studies by Marriott et al and Gulamhusein et al have analyzed His electrogram findings with simultaneous surface ECG findings and found low sensitivity and specificity of Ashman phenomenon for helping diagnose aberrancy versus ventricular rhythm.
- Aberration may also be a sign of intermittent ventricular preexcitation via an accessory pathway, as may occur with Wolff-Parkinson-White syndrome.
Medical Care
No treatment is needed for isolated complexes.
Medical/Legal Pitfalls
- Failure to diagnose and appropriately treat disease entities associated with Ashman phenomenon
- Failure to diagnose ventricular tachycardia
| Media file 1:
Ashman phenomenon illustrated by 12th and 15th beats, which follow a premature ventricular complex and long R-R cycle respectively. The underlying rhythm is atrial fibrillation. |
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Media type: ECG
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- Antunes E, Brugada J, Steurer G, et al. The differential diagnosis of a regular tachycardia with a wide QRS complex on the 12-lead ECG: ventricular tachycardia, supraventricular tachycardia with aberrant intraventricular conduction, and supraventricular tachycardia with anterograde conducti. Pacing Clin Electrophysiol. Sep 1994;17(9):1515-24. [Medline].
- Chaudry II, Ramsaran EK, Spodick DH. Observations on the reliability of the Ashman phenomenon. Am Heart J. Jul 1994;128(1):205-9. [Medline].
- Fisch C. Electrocardiography of arrhythmias: from deductive analysis to laboratory confirmation--twenty-five years of progress. J Am Coll Cardiol. Jan 1983;1(1):306-16. [Medline].
- Gouaux JL, Ashman R. Auricular fibrillation with aberration stimulating ventricular paroxysmal tachycardia. Am Heart J. 1947;34:366.
- Gulamhusein S, Yee R, Ko PT, Klein GJ. Electrocardiographic criteria for differentiating aberrancy and ventricular extrasystole in chronic atrial fibrillation: validation by intracardiac recordings. J Electrocardiol. Jan 1985;18(1):41-50. [Medline].
- Marriott HJL, Sandler JA. Criteria, old and new, for differentiating between ectopic ventricular beats and aberrant ventricular conduction in the presence of atrial fibrillation. Prog Cardiovasc Dis. 1966;9:18.
- Wagner GS. Ashman phenomenon. In: Wagner GS, Marriott HJ, eds. Marriott's Practical Electrocardiography. 9th ed. Baltimore, Md: Williams & Wilkins; 1994:. 340.
Ashman Phenomenon excerpt Article Last Updated: Mar 23, 2006
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