Dual Ventricular Rhythm

A74-year-oldmanwithahistoryofheart transplantpresentedwith alteredmental status. On admission, his bloodpressurewas96/63 mm Hg and his heart rate was 72/min. On examination, he was in no immediate distress and had clear lung fields. Therewere no gallopsonexamination, andhehadno focalneurologicaldeficits.Amedian sternotomy scar and a left upper chest medical device were noted. The patient was unable to provide any history. His relatives confirmed prior heart transplant. Figure 1 shows the initial electrocardiogram (ECG) at theemergency department. Question:Given theclinical historyand thisECG,what initial differential diagnoses should be considered and what should be the initial therapy?