23-05-2025
ECG Challenge: Palpitation Episodes in a COPD Patient
A 70-year-old man presents with a chronic obstructive pulmonary disease (COPD) exacerbation. He reports shortness of breath and palpitations. He has no known heart disease but has experienced palpitations in the past that were short-lived and did not require therapy.
Figure 1. Courtesy of Philip J. Podrid, MD.
The correct diagnosis is atrial fibrillation with Ashman's phenomenon (Figure 2).
Figure 2. Courtesy of Philip J. Podrid, MD.
Discussion
The rhythm is irregularly irregular, with no organized P waves. The average rate is 174 beats/min. The QRS complex duration (0.08 sec) and morphology are normal.
There are only three supraventricular rhythms that are irregularly irregular:
Sinus arrhythmia (one P wave morphology and stable PR interval)
Multifocal atrial rhythm (also called wandering atrial pacemaker) with a rate < 100 beats/min and multifocal atrial tachycardia with a rate > 100 beats/min (≥ 3 different P wave morphologies and PR intervals without any predominant P wave morphology)
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 (RBBB) morphology with an RSR' morphology in lead V1 (←) and a broad terminal S wave in lead V5 (→).
These complexes are not runs of NSVT, because they have a typical RBBB morphology and their intervals are also irregular. They are not the result of rate-related aberration, because there are other RR intervals as short or even shorter than these aberrated QRS complexes that are not associated with aberration. However, preceding the aberrated complexes is a long (┌┐)-short RR interval (└┘). This is the Ashman's phenomenon which is not caused by an abnormality in His-Purkinje conduction but rather by normal rate-related changes in His-Purkinje refractoriness or time for repolarization.
When the heart rate is slow (long RR interval), His-Purkinje refractoriness or time for repolarization prolongs whereas when the heart rate is fast (short RR interval), His-Purkinje refractoriness or time for repolarization shortens. This change in refractoriness or repolarization with heart rate is what causes the QT interval to change with heart rate, ie the QT interval is shorter at a faster heart rate and longer with a slower heart rate. When there is an abrupt change in heart rate 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. Most commonly the aberration is an RBBB, likely because the refractoriness of the right bundle is slightly longer than that of the left bundle.
