Electrophysiology testing before transcatheter pulmonary valve replacement in patients with repaired tetralogy of Fallot

Pathophysiology and management of adults with complex congenital heart disease after biventricular repair

Surgical management of congenital heart disease encompasses a spectrum of procedures, ranging from biventricular repair to univentricular palliation, each tailored to the specific anatomical and hemodynamic features of individual cases. Among these, biventricular repair, which preserves a functional ventricle to sustain pulmonary circulation, is prioritized whenever feasible. Advances in approaches have significantly improved outcomes, enabling many patients with congenital heart disease to reach adulthood, including the majority who have undergone biventricular repair. Despite these advancements, long-term complications-such as valvular disease, arrhythmias, heart failure, outflow tract obstruction, and dysfunction of extracardiac conduits-pose persistent challenges in the lifelong care of these patients. This review examines the distinct challenges and management strategies associated with adult patients who have undergone biventricular repair for complex congenital heart disease. The discussion focuses on key conditions, including repaired tetralogy of Fallot, transposition of the great arteries following atrial or arterial switch procedures, surgically managed or untreated congenitally corrected transposition of the great arteries with significant tricuspid regurgitation necessitating intervention, pulmonary atresia with intact ventricular septum, and Ebstein's anomaly. By addressing the long-term complications and therapeutic considerations unique to this patient population, this review aims to provide a comprehensive framework for optimizing care as these individuals transition into adulthood.

Age-Related Ventricular Tachycardia Substrate Characteristics for Repaired Tetralogy of Fallot Before Transcatheter Pulmonary Valve Placement

BACKGROUND

Ventricular tachycardia (VT) substrate characteristics before transcatheter pulmonary valve replacement (TPVR) in repaired tetralogy of Fallot (rTOF) are unknown.

OBJECTIVES

In this study, the authors sought to evaluate substrates for sustained monomorphic VT before TPVR in rTOF.

METHODS

Retrospective (2017 to 2021) and prospective (commencing 2021) rTOF patients with native right ventricular outflow tract referred for electrophysiology study (EPS) before TPVR were included. Electrophysiologic findings and outcomes of VT ablation were determined.

RESULTS

A total of 180 patients (mean age 39 ± 14 years, 54% male, 71 retrospective, 109 prospective) were identified. At EPS, monomorphic VT was induced in 45 (25%), and a slowly conducting anatomic isthmus alone was observed in 40 (22%). VT isthmus conduction velocity decreased (-0.08 m/s per decade; P = 0.008) and VT inducibility (P < 0.001 for trend) and cycle length (CL) (+15 ms per decade, P = 0.005) increased with age. Multivariable factors associated with shorter VT CL included preserved isthmus conduction velocity (-50 ms per m/s; P = 0.02), absence of atrial flutter (-18 ms; P = 0.007), and improved RV ejection fraction (-16 ms per 10% increase; P = 0.007). Catheter ablation was acutely successful in 80/83 (96%). At repeated EPS after a median of 5 months, previously ablated substrates were evident in 3/24 (13%) and new VT substrates in 3/33 (9%).

CONCLUSIONS

Pre-TPVR VT substrates in rTOF demonstrate age-related degeneration that was associated with VT inducibility and VT CL. Both recovery of VT isthmus conduction and new VT substrates were observed after TPVR despite successful catheter ablation.

Right Ventricular Electrophysiology and Arrhythmias in Adults With Congenital Heart Disease: Scientific Basis for Management

Right ventricular (RV) dysfunction and arrhythmias are major concerns in adults with congenital heart disease (CHD). The relationship between RV dysfunction and arrhythmogenesis is bidirectional, with structural and electrical remodeling contributing to arrhythmia development and, conversely, arrhythmias exacerbating RV failure. In addition to an RV in the standard subpulmonary position failing because of pressure and/or volume overload, other phenotypes associated with RV dysfunction in CHD include transposition of the great arteries with a systemic (subaortic) RV and univentricular hearts with a predominant RV morphology. The RV is better suited for low-pressure workloads. When it supports the systemic circulation, the RV undergoes remodeling changes that promote arrhythmias, which can provoke a cycle of worsening dysfunction and arrhythmogenesis. Arrhythmias can worsen RV dysfunction by impairing hemodynamic stability, reducing cardiac output, provoking dyssynchrony, and inducing tachycardia-induced cardiomyopathy. Cellular mechanisms, including myocardial fibrosis, dysregulation of ion channels, and abnormal gap junction function, are central to this process, facilitating both re-entrant and triggered arrhythmias. Conduction disturbances, whether inherent or caused by fibrosis or pacing, compound these effects, aggravating both RV dysfunction and arrhythmia perpetuation. Management strategies must be comprehensive and include pre-emptive approaches to minimize arrhythmias, alongside early detection. Individualized therapies may include catheter ablation and cardiac implantable electronic devices, with treatment tailored to the specific RV phenotype and arrhythmia type. In this review we emphasize the importance of personalized interventions to prevent the vicious cycle of RV dysfunction and arrhythmias in CHD. Further research is essential to optimize therapeutic strategies and address care-limiting knowledge gaps.

Slowly conducting anatomic isthmuses of tetralogy of Fallot: An opportunity for "prophylactic" ventricular tachycardia ablation

BACKGROUND

Patients with repaired tetralogy of Fallot are at risk of ventricular tachycardia (VT) and sudden cardiac death. Most VTs arise from 5 slowly conducting anatomic isthmuses (SCAIs; conduction velocity ≤0.5 m/s) bound by the right ventriculotomy, ventricular septal defect patch, and tricuspid and pulmonic valves. Historically, risk stratification electrophysiologic studies involved programmed ventricular stimulation with VT induction guiding implantable cardioverter-defibrillator (ICD) implantation or VT ablation.

OBJECTIVE

This study aimed to evaluate a "prophylactic" strategy of ablating SCAIs even in the absence of inducible VT to reduce ICD implantation and arrhythmic events and to compare this with the "historical" strategy.

METHODS

This was a single-center, retrospective cohort study. The historical cohort underwent programmed ventricular stimulation to guide ICD implantation or VT ablation. The prophylactic cohort underwent right ventricular electroanatomic mapping and ablation of SCAIs. A composite end point of arrhythmic death, cardiac arrest, sustained VT, and ICD complication was compared between the cohorts.

RESULTS

Ninety-two patients with repaired tetralogy of Fallot had risk stratification electrophysiologic studies. Of 57 prophylactic patients, SCAIs were identified or ablated in 33 (58%), 16 (28%) had inducible VT before ablation, and 1 received ICD. Of 35 historical patients, 15 (43%) had inducible VT; 3 had cryoablation during pulmonic valve replacement and 11 received ICDs. No prophylactic patients met the composite end point during a median 21 months (interquartile range, 8-35 months) vs 10 (29%) historical patients during a median 125 months (interquartile range, 90-142 months; P = .017). There were no ablation-related complications.

CONCLUSION

Prophylactic SCAI ablation is associated with fewer ICD implantations and a reduction in incident arrhythmic events without ablation-related complications.

Three-dimensional cardiac magnetic resonance allows the identification of slow-conducting anatomical isthmuses in tetralogy of Fallot

BACKGROUND AND AIMS

Patients with repaired tetralogy of Fallot remain at risk of life-threatening ventricular tachycardia related to slow-conducting anatomical isthmuses (SCAIs). Preventive ablation of SCAI identified by invasive electroanatomical mapping is increasingly performed. This study aimed to non-invasively identify SCAI using 3D late gadolinium enhancement cardiac magnetic resonance (3D-LGE-CMR).

METHODS

Consecutive tetralogy of Fallot patients who underwent right ventricular electroanatomical mapping (RV-EAM) and 3D-LGE-CMR were included. High signal intensity threshold for abnormal myocardium was determined based on direct comparison of bipolar voltages and signal intensity by co-registration of RV-EAM with 3D-LGE-CMR. The diagnostic performance of 3D-LGE-CMR to non-invasively identify SCAI was determined, validated in a second cohort, and compared with the discriminative ability of proposed risk scores.

RESULTS

The derivation cohort consisted of 48 (34 ± 16 years) and the validation cohort of 53 patients (36 ± 18 years). In the derivation cohort, 78 of 107 anatomical isthmuses (AIs) identified by EAM were normal-conducting AI, 22 were SCAI, and 7 blocked AI. High signal intensity threshold was 42% of the maximal signal intensity. The sensitivity and specificity of 3D-LGE-CMR for identifying SCAI or blocked AI were 100% and 90%, respectively. In the validation cohort, 85 of 124 AIs were normal-conducting AI, 36 were SCAI, and 3 blocked AI. The sensitivity and specificity of 3D-LGE-CMR were 95% and 91%, respectively. All risk scores showed an at best modest performance to identify SCAI (area under the curve ≤ .68).

CONCLUSIONS

3D late gadolinium enhancement cardiac magnetic resonance can identify SCAI with excellent accuracy and may refine non-invasive risk stratification and patient selection for invasive EAM in tetralogy of Fallot.

Transcatheter-Based Interventions for Tetralogy of Fallot Across All Age Groups

Tetralogy of Fallot (TOF) is the most common form of cyanotic congenital heart disease. Palliative procedures, either surgical or transcatheter, aim to improve oxygen saturation, affording definitive procedures at a later stage. Transcatheter interventions have been used before and after surgical palliative or definitive repair in children and adults. This review aims to provide an overview of the different catheter-based interventions for TOF across all age groups, with an emphasis on palliative interventions, such as patent arterial duct stenting, right ventricular outflow tract stenting, or balloon pulmonary valvuloplasty in infants and children and transcatheter pulmonary valve replacement in adults with repaired TOF, including the available options for a large, dilated native right ventricular outflow tract.

Multidetector Computed Tomography Assessment of Anatomical Ventricular Tachycardia Isthmuses in Repaired Tetralogy of Fallot

BACKGROUND

Tetralogy of Fallot (TOF) is associated with risk for sustained monomorphic ventricular tachycardia (VT). Preemptive electrophysiology study before transcatheter pulmonary valve placement is increasing, but the value of MDCT for anatomical VT isthmus assessment is unknown.

OBJECTIVES

The purpose of this study was to determine the impact of multidetector computed tomography (MDCT) in the evaluation of sustained monomorphic VT for repaired TOF.

METHODS

Consecutive pre-transcatheter pulmonary valve MDCT studies were identified, and anatomical isthmus dimensions were measured. For a subset of patients with preemptive electrophysiology study, MDCT features were compared with electroanatomical maps.

RESULTS

A total of 61 repaired TOFs with MDCT were identified (mean 35 ± 14 years, 58% men) with MDCT electroanatomical map pairs in 35 (57%). Calcification corresponding to patch material was present in 46 (75%) and was used to measure anatomical VT isthmuses. MDCT wall thickness correlated positively with number of ablation lesions and varied with functional isthmus properties (blocked isthmus 2.6 mm [Q1, Q3: 2.1, 4.0 mm], slow conduction 4.8 mm [Q1, Q3: 3.3, 6.0 mm], and normal conduction 5.6 mm [Q1, Q3: 3.9, 8.3 mm]; P < 0.001). A large conal branch was present in 6 (10%) and a major coronary anomaly was discovered in 3 (5%). Median ablation lesion distance was closer to the right vs the left coronary artery (10 mm vs 15 mm; P = 0.01) with lesion-to-coronary distance <5 mm in 3 patients.

CONCLUSIONS

MDCT identifies anatomical structures relevant to catheter ablation for repaired TOF. Wall thickness at commonly targeted anatomical VT isthmuses is associated with functional isthmus properties and increased thermal energy delivery.

Navigating Arrhythmias in Tetralogy of Fallot Throughout the Lifespan: A Case-based Review

Arrhythmias are a common complication associated with tetralogy of Fallot (ToF), one of the most prevalent forms of congenital heart disease. As illustrated by this case-based review, various forms of arrhythmias can be encountered across the lifespan of patients with ToF, from infancy to older adulthood. These include atrioventricular block, junctional ectopic tachycardia, and atrial and ventricular arrhythmias. Arrhythmias have important implications on the health and quality of life of patients with ToF and require treatment by caregivers with dedicated expertise. The choice of pharmacologic and/or interventional therapies to alleviate symptoms, avoid complications, and mitigate risks depends in part on the type, severity, and frequency of the arrhythmia, as well as on the particularities of individual clinical scenarios. Preventing, monitoring for, and managing arrhythmias are an integral component of the care of patients with ToF throughout their lifespan that is critical to optimizing health outcomes.