A man in his 60s with prior heart transplantation presented with intermittent syncope. Cardiac ultrasonography and laboratory examination showed normal left ventricular function and clinical examination did not reveal any evidence of rejection. During an episode of lightheadedness, the following 12-lead electrocardiogram (ECG) was obtained (Figure 1).
Question: What is the underlying atrial rhythm? What is the mechanism of this patient’s bradycardia?
Wright JM, Field ME. Syncope Following Orthotopic Heart TransplantSinoatrial or Atrioventricular Nodal Block?. JAMA Intern Med. 2016;176(7):1010-1012. doi:10.1001/jamainternmed.2016.1995