The Heart Of The Matter - A Case of Dyspnea on Exertion

An 86-year-old female with a past medical history of “a murmur” presents to the Emergency Department (ED) with a complaint of dyspnea on exertion for the past 2 days. Her heart rate in triage is 150 beats per minute (bpm), so she is immediately roomed in the resuscitation bay. An ECG is obtained, which demonstrates atrial fibrillation with rapid ventricular rate (RVR). The patient is started on appropriate treatment in consultation with Cardiology when the telemetry monitor begins to alarm. A repeat ECG is obtained (Figure 1).

Interpretation:

Rate: 192 bpm; Rhythm: narrow complex, irregularly irregular rhythm with run of regular, nonsustained, wide-complex beats; Axis: right axis deviation (I: neg., II: pos., aVF: pos.) Intervals: PR: n/a; QRS: 80, narrow & 120, wide; QT: n/a; P-Waves: absent; QRS Complex: narrow complex and wide complex present; ST Segment/T-waves: variable, T-wave inversions in lead III, aVF

What is on the differential for the nonsustained, wide-complex rhythm? And what are the next steps in management? What clues to the correct diagnosis are in the ECG?

Discussion:

As in this case, without obvious medical history to help direct our decision making, the differential for a wide complex tachycardia remains broad (Table 1).

Table 1. Etiologies of wide-complex tachycardia.

After consideration of the differential, the next best step is to get a repeat ECG or a rhythm strip and review the telemetry monitor alarm tracing. Upon closer review of the rhythm strip, a diagnostic identifier is noticed that adjusts the approach to current management (Figure 2).

Figure 2. Ashman phenomenon.

Ashman phenomenon is described as an aberrant ventricular conduction, usually of right bundle branch block (RBBB) morphology, which follows a short R-R interval and a preceding relatively prolonged R-R interval. Typically seen in atrial fibrillation, it is a mimic of non-sustained ventricular tachycardia (1). The long R-R interval leads to a longer refractory period in the His-Purkinje system. If a premature beat is conducted, evidenced by the following short R-R interval, the ventricle may still be caught in its refractory period, resulting in aberrant conduction and thus yielding the wide-complex morphology (2). RBBB is the most common aberancy due to the longer refractory period of the right bundle branch (3).

Proposed diagnostic criteria called the Fisch Criteria exist to help with differentiation of wide complex aberrations]:

• Long R-R cycle immediately before a short R-R cycle resulting in a wide-complex QRS is consistent with Ashman phenomenon;

• Short-long-short R-R pattern with less QRS width is less consistent with the diagnosis of Ashman phenomenon and suggests other causes;

• RBBB morphology with the normal orientation of the initial QRS vector suggests Ashman phenomenon;

• Irregular coupling of aberrant QRS complexes is common with Ashman phenomena and uncommon with PVCs, as normal coupling is seen with PVCs;

• Absence of a full compensatory pause is consistent in the Ashman phenomenon, and the presence of a full compensatory pause is more consistent with PVCs (2).

Management of the Ashman phenomenon, whether a single beat or non-sustained wide-complex tachycardia occurs, involves addressing the underlying atrial arrhythmia - in this case, atrial fibrillation with RVR (2).

Ultimately, the patient in this case was admitted to the CCU for rate control with digoxin and further electrophysiology (EP) work-up. The patient obtained adequate rate control with digoxin and was discharged from the hospital.

Take Away Points:

• When you notice a telemetry alarm, pause, carefully review the rhythm and ECG, and think through your differential before acting or changing management.

• For short runs of non-sustained wide-complex tachycardia, remember to consider Ashman phenomenon (in addition to normal sinus tachycardia and multi-geminal PVCs) if the presenting rhythm is atrial fibrillation.

• If there is ever a concern for non-sustained ventricular tachycardia, place pads on the patient, and get Cardiology involved early.

Authored by Michael Hohl, MD and Ari Edelheit, MD.

References:

1. Cadogan M, Buttner R, Buttner MC and R. Ashman phenomenon. Life in the Fast Lane [Internet]. January 2023. Available from: https://litfl.com/ashman-phenomenon/.

2. Grigg WS, Pearlman JD, Nagalli S. Ashman Phenomenon. StatPearls [Internet]. January 2025. Available from: https://www.ncbi.nlm.nih.gov/books/NBK562311/.

3. Singla V, Singh B, Singh Y, Manjunath CN. Ashman phenomenon: a physiological aberration. BMJ Case Rep. 2013;2013:bcr2013009660. Published 2013 May 24. doi:10.1136/bcr-2013-009660.