Top Things to Know: Arrhythmias in Repaired Tetralogy of Fallot (rTOF)
Published: October 20, 2022
Prepared by Barbara Entl, MD, Science and Medicine Advisor, American Heart Association
- Arrhythmia and sudden cardiac death remain common in repaired tetralogy of Fallot (rTOF) and affect even those with excellent anatomic repairs. Nonetheless, arrhythmias remain a major source of morbidity and mortality for adults with repaired TOF. This scientific statement explores the mechanisms for and treatment of atrial and ventricular arrhythmias in patients with rTOF.
- The mechanisms of arrhythmia in patients with rTOF are often distinct from those in patients with acquired heart disease. Most arrhythmias in TOF result from macro-reentrant circuits, which are a consequence of both the underlying anatomy and the methods used for repair with considerable heterogeneity depending on the lesion severity and the era of repair.
- Adult TOF patients have increased risk for developing reentrant atrial arrhythmias (AA), including intra-atrial reentrant tachycardia and cavo-tricuspid isthmus dependent atrial flutter (AFL). Cavo tricuspid isthmus dependent AFL and right atriotomy scar account for most of the intra-atrial reentrant tachycardia in TOF.
- The optimal approach to treat atrial arrhythmias in patients with TOF continues to evolve. In general, catheter ablation is more effective than antiarrhythmic drugs for the treatment of AFL and intra-atrial reentrant tachycardia. An initial rhythm control management is preferred over a rate control strategy for moderate and complex congenital heart disease, including TOF.
- Surgical AA ablation at the time of pulmonary valve replacement may decrease future arrhythmia risk and may be considered based on individual scenarios with a multidisciplinary team. Given the complex atrial substrate in the TOF patient, a hybrid approach may be required, comprising medications, pacing, and further surgery tailored to the individual.
- Ventricular arrhythmias (VA) remain a concern in adults with TOF throughout the lifespan and identifying patients at increased risk for life-threatening ventricular arrhythmias remains an enormous clinical challenge. The true incidence of ventricular arrhythmias is unknown but is likely the leading mechanism of sudden cardiac death in this population.
- Monomorphic ventricular tachycardia (VT) is the predominant form of VA. As is the case with VT in many forms of structural heart disease, such as ischemic cardiomyopathy, the prevailing mechanism of arrhythmia is macro-reentry. However, specific to patients with repaired TOF, reentry occurs with a critical circuit traversing well-defined anatomic isthmuses.
- The mechanism of ventricular arrhythmia is usually due to a consistent and discrete set of slowly conducting anatomic isthmuses related to both the native anatomy and the consequences of the surgical repair which interact with ventricular remodeling to provide arrhythmic substrate. This substrate can be identified during electroanatomic mapping and prophylactically ablated in appropriate patients.
- Electroanatomic contact mapping involves determining the anatomical unexcitable boundaries (no capture at high output pacing) and determining the conduction velocity through the anatomic isthmuses during sinus rhythm (in case of baseline RBBB) or pacing close to the anatomic isthmuses (in case of narrow QRS).
- Because the predominant mechanism of monomorphic VT in TOF is related to slowly conducting anatomic isthmus, an empiric surgical ablation line connecting the boundaries of the isthmus at the time pulmonary valve replacement may be a reasonable alternative to mapping guided ablation. Patients with VA, especially polymorphic VT that is not amenable to catheter ablation may benefit from beta blockade. If this strategy is ineffective, a class III antiarrhythmic may be considered.
- Some patients are inducible for very rapid non-tolerated VT or VT which rapidly degenerates into ventricular fibrillation. In these patients, even after an apparently successful ablation, repeat mapping and programmed ventricular stimulation or shared decision-making regarding placement of an ICD may be considered.
Krieger EV, Zeppenfeld K, DeWitt ES, Duarte VE, Egbe AC, Haeffele C, Lin KY, Robinson MR, Sillman C, Upadhyay S; on behalf of the American Heart Association Adults With Congenital Heart Disease Committee of the Council on Lifelong Congenital Heart Disease and Heart Health in the Young and Council on Clinical Cardiology. Arrhythmias in repaired tetralogy of Fallot: a scientific statement from the American Heart Association. Circ Arrhythm Electrophysiol. 2022;15:e000084. doi: 10.1161/HAE.0000000000000084