Faculty Bibliography

BACKGROUND:Catheter ablation of sustained monomorphic ventricular tachycardia (SMVT) guided by the identification of slowly conducting anatomical isthmuses (SCAIs) has been proposed to mitigate the risk of ventricular tachycardia in tetralogy of Fallot (TOF). However, the prevalence and clinical significance of SCAI remain uncertain. OBJECTIVES/OBJECTIVE:This study aimed to assess the association between SCAI and SMVT inducibility in patients with TOF. METHODS:A multicenter international cohort with retrospective (2017-2021) and prospective (commencing 2021) components enrolled patients with TOF referred for electrophysiological study before transcatheter pulmonary valve replacement. The proportion with SCAI and its association with SMVT inducibility were analyzed. RESULTS:A total of 162 patients (mean age 39.5 ± 14.2 years; 57.4% male) were included. SMVT was induced in 42 (25.9%) patients, and ≥1 SCAI was present in 76 (46.9%) patients. The prevalence of SCAI was higher in patients with inducible SMVT (78.6% vs 31.1%; P < 0.001). However, 21.4% of patients with inducible SMVT had normally conducting anatomical isthmus (14.3%) or a non-anatomical isthmus substrate (7.1%). The area under the curve of SCAI in predicting SMVT inducibility was 0.71 (sensitivity 78.6%; specificity 64.2%). Although SCAI was independently associated with SMVT (OR: 6.4; 95% CI: 2.6-18.2), the association with other clinical parameters improved prediction of SMVT inducibility. CONCLUSIONS:SCAI is highly prevalent in patients with TOF and is associated with inducible SMVT. However, the proportion of SCAI in noninducible patients is substantial, and some inducible patients have no SCAI. These findings suggest that SCAI alone is insufficient for arrhythmia management decisions, highlighting the need for an integrative approach combining electrophysiological study with other clinical parameters.

Short QT Syndrome is a rare inherited arrhythmia disorder marked by accelerated repolarization and a short QT interval. It carries a high risk of atrial and ventricular arrhythmias, including sudden cardiac arrest. Genetic mutations are identified in 20% to 30% of cases, most commonly in potassium channel genes (KCNH2, KCNQ1, KCNJ2). Management includes ICD implantation for secondary prevention and antiarrhythmic therapy, with quinidine being the most established agent for QT prolongation and arrhythmia suppression.

BACKGROUND:Although sustained monomorphic ventricular tachycardia (MVT) in repaired tetralogy of Fallot (TOF) is linked to abnormally conducting anatomical isthmuses, the clinical importance of inducible polymorphic ventricular tachycardia (PVT) is unclear. OBJECTIVES/OBJECTIVE:The aim of this study was to determine the clinical and electrophysiological characteristics of inducible PVT in TOF. METHODS:Patients from the ongoing CATAPULT-TOF (Catheter Ablation of Ventricular Tachycardia Before Transcatheter Pulmonary Valve Replacement in Repaired Tetralogy of Fallot) registry with inducible sustained PVT at index electrophysiology study were included. Abnormal anatomical isthmus was defined as conduction velocity <0.5 m/s. Centrally adjudicated episodes with ≥3 consecutive beats of similar morphology (10 of 12 leads) were labeled transiently organized PVT (TO-PVT). TO-PVT was analyzed in relation to three-dimensional substrate characteristics and postablation inducibility. RESULTS: = 0.001). CONCLUSIONS:Patients with inducible PVT display a lower clinical risk profile and healthier myocardial substrate than those with MVT. Organized beats at episode onset appear to be associated with anatomical isthmuses that can be targeted by catheter ablation.

BACKGROUND:The optimal pacemaker programming strategy for infants with isolated congenital complete atrioventricular block (CCAVB) remains unresolved. Dual-chamber pacing maintains atrioventricular synchrony and physiological heart rate variability but increases the burden of ventricular pacing on a myocardium that may be inherently prone to left ventricular (LV) dysfunction. OBJECTIVES/OBJECTIVE:This study sought to compare clinical outcomes of dual (DDD)- vs single (VVI)- chamber pacing in infants with CCAVB (DAVINCHI). METHODS:A multicenter retrospective study (2006-2023) identified infants with CCAVB and pacemaker implant at <1 year, with single-site ventricular pacing and no significant congenital heart disease. Outcome measured were clinically significant LV dysfunction, mortality, and complications. RESULTS:A total of 109 infants (64% autoimmune CCAVB) were identified, 60.6% had VVI pacing. Over a median follow-up of 5 years, 60 complications occurred in 47 subjects (43.1%). Smaller infants had more complications. Clinically significant LV dysfunction developed in 11 (10.1%) and was more frequent in DDD (21% vs 3%; P = 0.006). LV dysfunction resulted in mortality in 1 patient and 10 patients required a change in pacing mode. Independent risk factors for LV dysfunction were DDD pacing and neonatal implant. Right ventricular pacing lead placement had a higher HR (HR: 2.67) for LV dysfunction but was not statistically significant (P = 0.2). CONCLUSION/CONCLUSIONS:DDD pacing increases LV dysfunction risk compared with VVI in infants with CCAVB. Single-chamber LV apical pacing should be considered in infants with isolated CCAVB who require pacing. There is a high risk of pacing-related complications, particularly with an increased risk of ventricular lead complications in low-weight neonates.

BACKGROUND:Ventricular tachycardia (VT) substrate characteristics before transcatheter pulmonary valve replacement (TPVR) in repaired tetralogy of Fallot (rTOF) are unknown. OBJECTIVES/OBJECTIVE: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:One-hundred eighty 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.

Arrhythmias are highly prevalent in adults with congenital heart disease. For the clinician caring for this population, an understanding of pathophysiology, diagnosis, and management of arrhythmia is essential. Herein we review the latest updates in diagnostics and treatment of tachyarrhythmias and bradyarrhythmias, all in the context of congenital anatomy, hemodynamics, and standard invasive palliations for congenital heart disease.

Vascular rings are arterial malformations that lead to the compression of the trachea and/or esophagus. While "tight" rings often produce symptoms and require surgery, "loose" rings rarely produce symptoms. Given advances in fetal echocardiography, this diagnosis is now more often made prenatally. This poses a new conundrum in the management of asymptomatic patients, leading to practice variation and creating a target for clinical system improvement. Hence, we conducted this survey aiming to demonstrate the practice variation existing in current evaluation and management of these patients. An anonymous web-based survey was distributed to several listservs for pediatric cardiologists and pediatric cardiothoracic surgeons. Survey questions targeted respondent practice characteristics, testing obtained, and indications for testing or surgical referral. In total 61 responses were received, predominantly from pediatric cardiologists (95%) in the United States (97%). About 60% of clinicians reported frequently diagnosing patients with vascular rings by fetal echocardiogram, with only about 20% diagnosing them frequently on evaluation of symptoms. Computed tomography angiography and echocardiogram were the most common imaging modalities employed. Most clinicians obtained cross-sectional imaging at the time of diagnosis and referred to surgery once patients had at least occasional symptoms. Respondents demonstrated a low degree of agreement (Krippendorf's alpha 0.48). Few statistically significant patterns were identified between respondents based on their practice characteristics. This study identified significant variation between clinicians regarding the evaluation and management of vascular rings. Further research or expert opinions may help to standardize practice, saving costs and improving the quality of care for affected patients.

BACKGROUND:Thromboembolic events related to invasive electrophysiology studies, while rare, can have devastating consequences. Use of systemic anticoagulation for a pediatric or adult-congenital invasive electrophysiology study is recommended, however there is no established standard of practice in this population. OBJECTIVE:To report on procedural practices for thromboembolism prophylaxis during invasive electrophysiology studies for pediatric patients and adults with congenital heart disease. METHODS:An anonymous web-based survey was sent to the members of the Pediatric and Congenital Electrophysiology Society. The survey focused on pre-procedural, intra-procedural, and post-procedural thromboembolism prophylaxis practices during invasive electrophysiology studies. Significant practice variation was defined as <90% concordance among respondents. RESULTS:Survey was completed by 73 members; 52 (71%) practicing in the United States, 65 (89%) practicing in an academic institution, and 14 (19%) in an institution that performs more than 200 invasive electrophysiology procedures annually. Responses showed significant variation in practice. Prior to an invasive electrophysiology procedure, 25% discontinue aspirin while 47% discontinue anticoagulants. Heparin is given for all procedures by 32%. When heparin is administered, the first dose is given by 32% after sheaths are placed, 42% after crossing into the systemic atrium, and 26% just prior to systemic-side ablation. Most target an activated clotting time between 200-300 seconds. Post systemic-side ablation, 58% do not initiate a heparin infusion. Post-procedural oral agents were initiated on day of procedure by 34% of respondents and on post-procedure day 1 by 53%. If treating with aspirin, 74% use low-dose (3-5 mg/kg or 81 mg daily), and 68% treat for 4-6 weeks. CONCLUSION:There is significant variation in thromboembolism prophylaxis for invasive EP studies among pediatric and congenital electrophysiologists. Further studies are needed to optimize the management of thromboembolism prophylaxis in this population.

Epicardial cardiac implantable electronic device implant remains a common option in pediatric patients and certain patients with congenital heart disease due to patient size, complex anatomy, residual intracardiac shunts, and prior surgery precluding transvenous implant. Advantages include the lack of thromboembolic and vascular risks and ability to implant during concomitant surgery. Significant disadvantages include the occurrence of lead dysfunction that can result in bradycardia events in pacemaker patients, inappropriate shocks in implantable cardiac defibrillator patients, and overall a more invasive procedure.