EXPLANATION


Arrhythmias remain a common cause of morbidity and mortality in patients after repair of Tetralogy of Fallot (ToF), with 43% of patients having sustained arrhythmias or needing intervention. As this patient population continues to grow and age, the incidence of both atrial and ventricular arrhythmia continues to increase as well. The mechanism of atrial and ventricular arrhythmias differs, but both can significantly impact long-term outcomes and management. Recent consensus statements discuss the incidence and mechanism of these arrhythmias, and more importantly, recommendations for risk stratification and management.


Of the patients with arrhythmias after ToF repair, 20% were atrial arrhythmias. These patients are at an increased risk of developing reentrant tachycardia, atrial flutter, and atrial fibrillation. Interestingly, as many as 38% of patients develop multiple types of atrial arrhythmias. The mechanism of atrial arrhythmia is most likely related to residual cardiac lesions associated with atrial dilation and/or tricuspid regurgitation. Common risk factors for the development of atrial fibrillation, including age, reduced ejection fraction, cardiac surgery, and left atrial dilation, are similar in the adult population with repaired ToF. Atrial arrhythmias are associated with worsened cardiovascular outcomes. Recommendations for management are evolving, but evidence supports ablation over medical management, with a focus on rhythm over rate control. Anticoagulation is also part of arrhythmia management per standard guidelines for stroke prevention. Additionally, patients are at risk for developing bradyarrhythmia after ToF repair and should follow standard guidelines for evaluation and management, which may require pacemaker insertion.


Ventricular arrhythmias are also common after ToF repair and are considered the most common cause of sudden cardiac death in this population. Monomorphic ventricular tachycardia is the most common ventricular arrhythmia observed in this patient population. The likely contributing factors include the original congenital cardiac defect and the type of surgical correction. Patch material, fibrosis, and valve annuli create areas of conduction block and substrate for reentrant electrical conduction. Risk factors for ventricular arrhythmias include age, QRS duration and morphology, type of surgical repair, ventricular dysfunction, and right ventricular hypertrophy. Management guidelines continue to evolve but focus on referring patients for an electrophysiology study with ablation and/or cardiac implantable electronic device insertion as primary or secondary prevention. Special consideration must be given to the patient population undergoing pulmonary valve intervention. Current guidelines support electrophysiology study and/or ablation before surgical or transcatheter pulmonary valve replacement in patients with the aforementioned risk factors.


The correct answer is C. Given the surgical history and Holter monitor results described for the patient in the stem, an electrophysiology study and possible ablation are appropriate before pulmonary valve replacement. Coronary angiography identifies coronary anatomy for surgical or transcatheter valve replacement but is invasive, and this information can often be obtained with computed tomography angiography. Routine pulmonary function testing is not necessary before surgery unless pulmonary disease is suspected to be the cause of this patient’s symptoms. In this case, the symptoms are readily explained by her cardiac history and diagnostic studies.


REFERENCES


Krieger EV, Zeppenfeld K, DeWitt ES, et al. Arrhythmias in repaired Tetralogy of Fallot: a scientific statement from the American Heart Association. Circ Arrhythm Electrophysiol. 2022;15(11):e000084.


Waldmann V, Bessière F, Gardey K et al. Systematic Electrophysiological Study Prior to Pulmonary Valve Replacement in Tetralogy of Fallot: A Prospective Multicenter Study. Circ Arrhythm Electrophysiol. 2023 Jun;16(6):e011745.