A 70-year-old man presents with an exacerbation of chronic obstructive pulmonary disease. He is complaining of shortness of breath as well as palpitations. He has no known heart disease but has experienced palpitations in the past that have been short-lived and never required any therapy. What is your diagnosis? Atrial fibrillation with nonsustained ventricular tachycardia Atrial fibrillation and Ashman phenomenon Atrial fibrillation and rate-related right bundle branch block Normal sinus rhythm with premature atrial contractions and nonsustained ventricular tachycardia Atrial flutter with variable block and nonsustained ventricular tachycardia Discussion The diagnosis is atrial fibrillation with a rapid ventricular response. This is known as Ashman phenomenon. The rhythm is irregularly irregular and there are no organized P waves. The average rate is 174 beats/min. The QRS complex duration is normal (0.08 sec) and there is a normal morphology. There are only three irregularly irregular supraventricular rhythms: sinus arrhythmia (one P wave morphology and stable PR interval); multifocal atrial rhythm with a rate < 100 beats/min; or multifocal atrial tachycardia with a rate > 100 beats/min (at least three different P wave morphologies and PR intervals without any P wave morphology being dominant) and atrial fibrillation in which there are no organized P waves. Therefore, this is atrial fibrillation. Noted are several QRS complexes that have an increased duration (0.12 sec) with a right bundle branch block morphology and an RSR' morphology in lead V1 (←), and a broad terminal S wave in lead V5 (→). These complexes are not the result of rate-related aberration because there are RR intervals equally as short or even shorter that are not associated with aberration. However, preceding the aberrated complexes, there is a long RR interval (┌┐) abruptly followed by a short RR interval (└┘). Given this information, this is Ashman phenomenon, which is not the result of an abnormality in His-Purkinje conduction but rather the result of normal rate-related changes in His-Purkinje refractoriness. When the heart rate is slow (a long RR interval), His-Purkinje refractoriness is prolonged; whereas with fast heart rates (a short RR interval), His-Purkinje refractoriness shortens. When there is an abrupt change in heart rate, going from slow (long RR interval) to fast (short RR interval), His-Purkinje refractoriness does not adapt or change immediately, and hence one or several QRS complexes are conducted with aberration. Almost always, the aberration is a right bundle branch block, likely because the refractoriness of the right bundle is slightly longer than that of the left bundle. Source
