Andersons pediatric cardiology 1909

cardiovascular risk factors can contribute only to a worse outcome.97 Arrhythmia (see also Chapter 22) Arrhythmia is a common problem in the Fontan population, has an increasing prevalence in older patients, and is often associated with Fontan failure The two most frequent arrhythmias are bradycardia due to sinus node dysfunction, and atrial flutter The latter is more correctly termed intraatrial reentrant tachycardia (IART) Both of these arrhythmias become more prevalent with time but are not necessarily linked to each other (Fig 73.10) In a population-based report, bradyarrhythmias are present in 7% at 10 years and 15% at 20 years after the Fontan procedure, and tachyarrhythmia in 9% and 31%, respectively.98 Tachyarrhythmia is commoner in those with functional limitations,99 isomerism, and an atriopulmonary Fontan connection when compared with the extracardiac Fontan.98,100,101 A contemporary series suggests atrial tachyarrhythmia is present in most if not all patients 25 years after the atriopulmonary Fontan procedure.102 The extracardiac Fontan may result in less IART than the lateral tunnel,103 although the evidence for this is less conclusive IART is also more common when atrioventricular valve repair or pulmonary vein surgery is required at the initial surgery.100 FIG 73.10 Cumulative proportions of arrhythmias encountered after the Fontan procedure (From Carins TA, Shi WY, Iyengar AJ, et al Long-term outcomes after first-onset arrhythmia in Fontan physiology J Thorac Cardiovasc Surg 2016;152[5]:1355–1363.) Focal, atrial ectopic tachycardias occur in approximately 13% of patients over long-term follow-up, many in the same patients who have IART.103 Atrial fibrillation is becoming more frequent in older patients (19% in one series)103 with risk factors overlapping those of the aging population (such as overweight and hypertension) The occurrence of bradyarrhythmia or tachyarrhythmia signals a 50% to 60% risk of Fontan failure over the next 10 years.98 Ventricular tachycardia (VT) is relatively uncommon and usually asymptomatic, with Holter recordings suggesting a prevalence of approximately 6% 10 years after Fontan.104 However, symptomatic VT or ventricular fibrillation can occur in up to 3%.10 The presence of VT correlates with larger ventricular volumes,104 reduced ejection fraction, and magnetic resonance imaging (MRI) evidence of myocardial fibrosis.105 Sudden cardiac death occurs at late follow-up in 5% to 9% Risk factors include the presence of atrial tachyarrhythmia,12 atrioventricular valve replacement at the time of the Fontan surgery, and an immediate postoperative systemic venous pressure greater than 20 mm Hg.103 Preoperative sinus rhythm is protective.102 Bradycardia and Pacing Pacemakers may be used in up to 25% of cases at late follow-up, including those implanted for the management of atrial tachycardia Pacing for bradyarrhythmia is required in approximately 7% to 15% of patients during long-term follow-up In approximately two-thirds, the indication is sinus bradycardia and, in onethird, atrioventricular block.98,106 The latter is more common among patients with congenitally corrected transposition of the great arteries (Fig 73.11) Pacemakers are commonly placed when an atriopulmonary Fontan is converted to an extracardiac Fontan This procedure usually includes antiarrhythmia surgery Some centers will implant biatrial antitachycardia pacing devices prophylactically during the same procedure.107