Abstract
A 56-year-old woman, known in her past medical history with uncorrected atrioventricular septal defect, secondary pulmonary hypertension, and permanent atrial fibrillation, with repeated hospitalizations for congestive heart failure over the years, presented to the Emergency Department for repeated syncopal episodes. Holter monitoring detected atrial fibrillation with periods of asystole. While most cases in the literature mainly focus on patients with isolated atrial septal defects (ASD)(1), we present a case of a challenging pacemaker implant in a patient with transitional atrioventricular septal defect (AVSD). The case illustrates the challenges of differential diagnosis of syncope and of implanting a pacemaker in adults with congenital heart disease, underscoring the importance of an excellent understanding of electrophysiology, defect anatomy, and postoperative alterations. In addition, this case emphasizes that structural heart disease can be a potential cause when assessing recurrent syncope. When selecting the implantation and pacing modes, operators must consider the possibility of multiple reimplantation throughout the patient’s lifespan.