A 65-year-old woman presents with palpitations and shortness of breath. Her initial vital signs include: BP 100/68, HR 180, R 26, O2sat 97%, 98.0°. A brief exam finds a mildly distressed woman, lungs clear, tachycardia, no peripheral edema. She has no history of atrial fibrillation, only hypertension and hyperlipidemia. Her medications include lisinopril and atorvastatin. An EKG is obtained (Below: Atrial fibrillation with ventricular rate of 180/minute with four wide-complex beats best seen in lead V1 and lead II rhythm strip).
The wide-complex beats might be of concern for ventricular ectopy, but there is another, more benign explanation.
Ashman’s phenomenon describes an occurrence during rapid irregular rhythms (typically atrial fibrillation, but also with multifocal atrial tachycardia – MAT) when wide-complex, aberrantly conducted beats may appear to be ventricular in origin. The repolarization interval for any QRS complex (electrocardiographically, the QT interval) is proportional to the R-R interval that precedes it. When, during atrial fibrillation, a long R-R interval occurs, the subsequent repolarization will take more time. Therefore, when by chance you have a long R-R interval followed by a short R-R interval, the complex ending the short interval may find a portion of the conducting system not yet fully repolarized. Since the portion of the conduction system that is predictably slowest to repolarize is the right bundle, Ashman beats typically have RBBB morphology. RBBB morphology includes a tall R-wave in V1 and wide terminal S-waves in the lateral leads.
Nothing is 100% certain, but if a wide-complex beat with RBBB morphology ends a short R-R following a long R-R, that wide beat is most likely an aberrantly conducted supraventricular beat. And if subsequent beats are also at a rapid rate, they will continue to conduct aberrantly, appearing as couplets or runs of wide-complex tachycardia. Just remember: LONG – SHORT – WEIRD for Ashman beats!
1. A 25-year-old man presents with palpitations after an evening of partying, including the use of cocaine. The rhythm is atrial fibrillation with a rapid ventricular response. The wide beats could be of concern if interpreted as frequent PVCs in a young man after cocaine use. However, Ashman’s phenomenon predicts that all these wide beats are supraventricular in origin. This is a V1 rhythm strip with a tall R wave—thus RBBB morphology of the wide beats.
2. A 78-year-old man is being observed after presenting with chest pain. Nurses are concerned by a “three beat run” of wide-complexes. “Isn’t this ventricular tach?” they ask. Fortunately, you can explain that the wide beats are aberrantly conducted supraventricular beats as predicted by Ashman’s phenomenon.
Now that you know what causes it, look for Ashman’s phenomenon in your next patient with rapid AF. You may find it’s fairly common. Fortunately, it’s benign, so you can focus on treating the underlying disorder.