Electrophysiology issues in adult congenital heart disease

Improved surgical outcomes in children have led to a growing population of adults with congenital heart disease. Rhythm disturbances in the adult congenital heart disease (ACHD) patient can be intrinsic to the anomaly or acquired after palliation. Tachyarrhythmias, either supraventricular or ventricular, and bradyarrhythmias, either sinus node dysfunction or atrioventricular block, may occur frequently. Technological advances in intervention and surgical approaches have led to prophylactic and therapeutic reduction in arrhythmias. In order of escalation, this article addresses medical management, catheter ablation, device therapy for antitachycardia pacing and defibrillation, and surgical intervention. There are now an estimated one million-plus ACHD patients living in the United States. An estimated 45% of those have simple defects (e.g., atrial septal defects), 40% have moderately complex defects (e.g., tetralogy of Fallot, or ToF), and 15% have severely complex defects (e.g., single ventricle anatomy or surgical palliations for transposition of the great arteries [TGA]). The moderate and severe categories have a high incidence of arrhythmia. Of older repaired ToF patients, 34% develop symptomatic atrial or supraventricular tachycardias, 8.5% develop high-grade ventricular tachycardia (VT), and there are an increasing number of implantable defibrillators due to a sudden-death estimate of 2% per decade. Thus, an estimated 50,000 adults with repaired ToF will require electrophysiology follow-up with 100 sudden deaths per year nationally. Roughly 3% of all congenital heart surgeries requiring cardiopulmonary bypass have post-operative AV block, and 1% will require permanent pacing. Older atriopulmonary Fontans have up to an estimated 50% incidence of atrial tachycardia within a decade of palliation due to suture lines and elevated atrial pressures. Patients who have undergone an atrial switch operation (e.g., Mustard or Senning operations) are rarely exclusively in sinus rhythm a decade after repair, thus posing problems for rhythm control and anticoagulation. Catheter ablation in congenital heart disease is often more challenging than structurally normal hearts because of abnormal anatomy (congenital and/or post-surgical) and thicker chamber walls due to unfavorable hemodynamics. In preparation, review of noninvasive imaging, previous catheterization angiography, and surgical palliation reports are paramount prior to a procedure. Fortunately, to meet the growing challenge, newer software with 3-D packages allow for improved mapping. In addition, advances with larger-tipped and irrigated-tip catheters allow for deeper, more effective lesions to be placed. Several advances in surgical approach have led to a reduction in arrhythmias. For example, the arterial switch operation for d-transposition of the great arteries instead of the aforementioned atrial switch operation eliminates the use of a systemic right ventricle that can later develop intra-atrial reentrant tachycardia and sinus node dysfunction. Other advances include paying careful attention to minimizing ventriculotomies in ToF and ventricular septal defect (VSD) repairs, earlier complete repairs, and valve sparing to reduce pulmonary insufficiency. Finally, completion of the extra-cardiac Fontan procedure (e.g., total cavopulmonary connection) for single ventricles avoids extensive suture lines in the right atrium, thereby reducing scarring and higher pressures that lead to IART and sinus node dysfunction. Extracardiac (EC) conduits and lateral tunnel (LT) Fontans are preferred today, and the Fontan conversion procedure (converting prior atriopulmonary Fontans to the EC or LT type) can be performed to reduce arrhythmia and thromboembolic events.