Ashman phenomenon: an often unrecognized entity in daily clinical practice.

We decided to reply with this letter regarding the entity that is often unrecognized in daily clinical practice. Ashman phenomenon is an aberrant ventricular conduction most frequently seen during atrial fi brillation. Th is phenomenon is an intraventricular conduction abnormality caused by a change in the heart rate. Ashman beat is typically seen when a relatively long cycle is followed by a relatively short cycle1. Th e beat with a short cycle often has right bundle-branch block (RBBB) morphology (Fig. 1a). Th is phenomenon may cause diagnostic confusion with premature ventricular complexes (PVCs) (Fig. 1b), and a series of consecutive aberrantly conducted supraventricular impulses may be mistaken for ventricular tachycardia (Fig. 1c). Th e pathophysiology of Ashman phenomenon depends on the relative refractory period of the conduction tissues and the heart rate. Th e duration of the refractory period of the heart muscle is proportional to the R-R interval of the preceding cycle. A longer cycle will prolong the ensuing refractory period, and if a shorter cycle follows the beat terminating the cycle is likely to be conducted with aberrancy. Th e refractory period of the right bundle-branch is longer than the left one and it will still be in the refractory period when supraventricular impulse reaches the HisPurkinje system resulting in a complex with RBBB2,3. Ashman phenomenon is principally diagnosed by a 12-lead surface electrocardiogram (ECG). Rarely, in diffi cult cases, invasive electrophysiological studies will be required to establish the source of an arrhythmia whether supraventricular or ventricular4. For daily use, useful criteria to establish the diagnosis of Ashman phenomenon are those described by Fisch5: 1) relatively long cycle immediately preceding the cycle terminated by the aberrant QRS complex; 2) RBBB-form aberrancy with normal orientation of the initial QRS vector, a series of wide QRS supraventricular beats is possible; 3) irregular coupling of aberrant QRS complexes; and 4) lack of fully compensatory pause. Clinically, Ashman phenomenon by itself is asymptomatic and does not require any specifi c treatment. Finally, although Ashman phenomenon has been known for more than sixty years now1, it still often stays unrecognized, or misdiagnosed as PVCs. Understanding Ashman phenomenon is useful and necessary in daily clinical practice because, for example, in 24-hour Holter ECG records we can fi nd even several thousand wide QRS complexes caused by Ashman phenomenon. It usually occurs with atrial fi brillation, and atrial fi brillation is the most common sustained cardiac rhythm disturbance, increasing in prevalence with age6. Furthermore, not only the cardiologists, but often physicians of diff erent profi les such as neurologists, anesthesiologists, general practitioners, etc. see it and treat it.