A previously healthy person in their 60s with progressive shortness of breath and fatigue for the past 6 months presented to the emergency department with palpitations and shortness of breath. The patient’s simultaneously recorded 3-lead rhythm electrocardiogram (ECG) on presentation is shown in the Figure, A, and results of a 12-lead ECG after receiving intravenous amiodarone are shown in Figure, B.
Questions: How would you interpret the initial rhythm strip and 12-lead ECG findings recorded after receiving amiodarone?
The initial 3-lead rhythm ECG revealed salvos of wide QRS complex tachycardia that terminated spontaneously and were separated by several sinus rhythm beats. The sixth and fifteenth QRS complexes were fusion complexes with an intermediate morphology between the sinus conducted QRS complex (fifth and sixteenth QRS) and the wide QRS complex tachycardia (best appreciated in leads V1 and V5) (Figure, A). The fusion complexes confirmed that the wide QRS complex salvos represent ventricular tachycardia (VT). Retrograde P waves can be observed in lead V1 in the ST-T waves after the first to fourth and the eighth to twelfth QRS complexes by comparing them to the ST-T waves after the seventh QRS complex. The wide QRS complex tachycardias terminated with retrograde P waves after the fourth and twelfth QRS complexes. This finding confirmed VT with retrograde conduction because in atrial tachycardia with aberrant conduction atrial activity drives ventricular activity and the tachycardia will thus terminate with a QRS complex.