Arrhythmic risk in repaired Tetralogy of Fallot
Patients with repaired Tetralogy of Fallot (ToF) represent a population with a well-recognised risk of ventricular arrhythmias and sudden cardiac death. Surgical scars and prosthetic material may create the anatomical substrate for re-entrant arrhythmias and remain an important contributor to late morbidity and mortality in this population. Previous studies have shown that arrhythmic burden in adults with repaired ToF is clinically relevant and is associated with variables such as age, prolonged QRS duration, previous surgical procedures and ventricular dysfunction (1). In addition, consensus documents have highlighted the complexity of arrhythmia management in adults with congenital heart disease, particularly when post-surgical anatomical substrates and pulmonary valve prostheses coexist (2).
For this reason, pulmonary valve replacement is of particular interest because of its potential both to modify ventricular arrhythmia burden and to interfere with subsequent catheter ablation. In this context, the development of transcatheter pulmonary valves (TPV) raises the question of whether contact between prosthetic material and native myocardial tissue may increase arrhythmic burden. Previous small series have reported ventricular arrhythmias after transcatheter pulmonary valve implantation, usually as a transient phenomenon, but the issue requires further study (3-5).
The SERVE registry: study design and patient population
The study by Armstrong et al., published in JACC: Clinical Electrophysiology, analyses the incidence, temporal evolution and factors associated with ventricular arrhythmias (VA) after self-expanding transcatheter pulmonary valve replacement (TPVR) in patients with congenital heart disease. This was an analysis from the multicentre SERVE registry, which included 513 patients from 25 centres in the United States who underwent TPVR between March 2021 and September 2024.
The median age was 28 years. ToF was the predominant underlying congenital heart disease, present in 68% of patients, followed by congenital pulmonary stenosis in 22%. Among patients with ToF, most had a transannular patch. A Harmony TPV valve was implanted in 359 patients, whereas 154 patients received a 29-mm Sapien 3 valve mounted within the Alterra Adaptive Pre-stent System.
The main objective of the study was to characterise VA during the first six months after implantation and to compare outcomes between the two valve platforms. In the registry, the definition of VA was broad and included non-sustained ventricular tachycardia (NSVT), sustained monomorphic ventricular tachycardia (SMVT), polymorphic ventricular tachycardia or ventricular fibrillation (PVT/VF), or a ventricular ectopy (VE) burden greater than 1% on Holter monitoring. Severe ventricular arrhythmic events (SVAE) were defined as SMVT, PVT, VF, syncope due to ventricular tachycardia, cardioversion or defibrillation for ventricular tachycardia or ventricular fibrillation, or appropriate implantable cardioverter-defibrillator (ICD) therapy. Ventricular arrhythmia burden was assessed at baseline, during the procedural admission and at six-month follow-up, defined as any clinical follow-up performed between 120 and 240 days after implantation. Rhythm monitoring at follow-up and the need for electrophysiological study (EPS) were left to the discretion of each centre.
Ventricular arrhythmias during the early post-procedural period
During the procedural admission, 29% of patients developed VA, more than 90% of which were NSVT. The incidence was higher among patients treated with the Alterra system than among those treated with Harmony, 37% versus 26%, respectively. In multivariate analysis, higher right ventricular ejection fraction (RVEF) and the Alterra system were associated with VA, whereas baseline antiarrhythmic therapy and older age were associated with a lower risk. Alterra was also associated with a greater need for antiarrhythmic treatment during hospitalisation and with a higher rate of delayed discharge due to arrhythmia. The need for invasive treatment was uncommon, although new antiarrhythmic therapy was started in 22% of patients.
Six-month follow-up and temporal evolution of arrhythmic burden
At six-month follow-up, arrhythmic burden had clearly decreased. The overall prevalence of VA was 9.6%, although it remained higher in the Alterra group than in the Harmony group. SVAE at six months were rare, occurring in approximately 0.6% of patients, and four deaths were reported, none of which was clearly attributed to an arrhythmic event. The need for ICD implantation or EPS remained low, and the valve frame did not prevent effective ventricular tachycardia ablation in any case. In multivariate analysis, baseline ventricular arrhythmia burden and the Alterra system were associated with ventricular arrhythmias at follow-up, whereas no protective factor was identified.
Another relevant aspect of the study is the longitudinal analysis of VA. Using mixed-effects models, the authors observed a significant increase in VA burden during the procedural admission, from 13% at baseline to 27%, followed by a significant decrease at six months to approximately 7%. In patients receiving a Harmony valve, the arrhythmic burden decreased below baseline levels, whereas in patients receiving the Alterra system it returned approximately to baseline.
Potential mechanisms and differences between valve platforms
The temporal pattern of VA supports the hypothesis of a predominantly transient phenomenon, probably related to acute mechanical irritation of the right ventricular outflow tract myocardium by the prosthesis. However, the persistent association between Alterra and VA at six months suggests that relevant differences in geometry, radial force, myocardial contact or patient anatomical selection may exist.
The other predictor of VA during the procedural admission was higher RVEF. The authors suggest that a less fibrotic right ventricle may contain more viable myocardial tissue and therefore be more susceptible to mechanically induced VA when it contacts the prosthetic frame.
Strengths and limitations of the study
The main strengths of the study are its sample size, its multicentre nature and the direct comparison between two contemporary self-expanding TPV platforms. Nevertheless, several limitations should be considered. This was an observational, non-randomised registry, and therefore confounding by indication is likely. Device selection was probably influenced by right ventricular outflow tract anatomy, operator preference and technical criteria that may not be fully captured in the study. In addition, rhythm monitoring was heterogeneous, with only a minority of patients undergoing Holter monitoring before, during and after the procedure. Six-month follow-up was available in only 65% of the cohort, introducing a potential follow-up bias. Finally, the definition of VA was broad and combined clinically severe arrhythmias, such as sustained ventricular tachycardia or VF, with lower-risk findings such as NSVT or VE burden. This may limit the interpretation of clinically relevant arrhythmic events.
Clinical implications and future perspectives
This study shows that ventricular arrhythmias are frequent after self-expanding TPVR, particularly during the immediate post-procedural period and with a higher observed incidence in patients receiving the Alterra system. However, most arrhythmias were NSVTs, showed a tendency to normalise at six months, and severe arrhythmic events were rare. These findings support close rhythm surveillance after the procedure, but do not, by themselves, justify major changes in the indication for transcatheter pulmonary valve replacement or the systematic use of preventive invasive strategies. Prospective studies with standardised rhythm monitoring and longer follow-up are needed to determine whether these arrhythmias have long-term prognostic implications.