PC2147: Management of Adult Fontan Patient with Unstable Sinus Bradycardia

Introduction: Adult patients with complex congenital heart disease (CCHD), specifically those who have undergone a Fontan procedure, carry an increased arrythmia risk. Management of bradycardia in the setting of anatomical variance requires deviation from the standard adult algorithm.

Case Description: A 33-year-old female presented with three days of presyncope and associated nausea/vomiting. She had a past medical history of double outlet right ventricle, D-transposition of the great arteries with hypoplastic tricuspid valve/right ventricle, and subpulmonic ventricular septal defect for which she underwent staged single ventricle palliation, ultimately with an atriopulmonary Fontan procedure at age five years. Heart rate on presentation was 40 beats per minute (BPM). Electrocardiogram demonstrated sinus bradycardia with pauses, left axis deviation, and diffuse precordial lead T wave inversions (Figure 1). She was diagnosed with sick sinus syndrome secondary to atrial scarring from her Fontan procedure.
The patient was initiated on a dopamine drip for adequate chronotropy. Developing hemodynamically significant atrial tachycardia limited dopamine dosing; she was transferred to the adult cardiac intensive care unit (CICU) for consideration of temporary transvenous pacing. Bedside transthoracic and transesophageal echocardiogram showed a patent Fontan circuit, cavopulmonary anastomosis with enlarged atria, and echogenic material concerning for Fontan thrombus (Figure 2). Her anatomy, potential scarring, and concern for thrombus interfered with safe bedside temporary transvenous pacemaker (TVP) placement.
Pediatric electrophysiology (EP) was consulted. Ultimately, implantation of a permanent transvenous single chamber atrial pacing system was performed in the pediatric catheterization laboratory with fluoroscopic guidance. Lead placement success was dependent on the pediatric EP team using three-dimensional EP voltage mapping to identify the atrial location with optimal signal amplitude and minimal scarring.

Discussion: Despite the growing population of adult patients with CCHD, there is a paucity of data regarding the management of adult Fontan patients presenting with unstable arrythmias. Follow-up studies show that half of adult Fontan patients develop clinically significant arrhythmias.1,2 Like in this case, 13% of patients will develop sinus node dysfunction that requires pacemaker implantation, with approximately 50% of these patients presenting 30 years after their initial procedure.3 These adult patients are at increased risk of heart failure and secondary arrhythmias such as ventricular tachycardia leading to increased mortality.4 In typical adult patients, the protocol for unstable bradycardia leads to placement of a TVP, however Fontan anatomy and scarring can preclude effective TVP without pediatric EP guidance. Appropriate management requires an understanding of Fontan procedure complications that currently extends beyond the standard adult medicine training.

Conclusion: As patients with Fontan procedures are now achieving greater longevity, it becomes imperative for adult providers to familiarize themselves with the late procedural complications and subsequent management. Critically ill patients with CCHD can benefit from interdisciplinary collaboration between adult interventionalists, congenital cardiologists, and pediatric electrophysiologists for optimal care.