Disease severity, arrhythmogenesis, and fibrosis are related to longer action potentials in tetralogy of Fallot

BACKGROUND

Arrhythmias may originate from surgically unaffected right ventricular (RV) regions in patients with tetralogy of Fallot (TOF). We aimed to investigate action potential (AP) remodelling and arrhythmia susceptibility in RV myocardium of patients with repaired and with unrepaired TOF, identify possible correlations with clinical phenotype and myocardial fibrosis, and compare findings with data from patients with atrial septal defect (ASD), a less severe congenital heart disease.

METHODS

Intracellular AP were recorded ex vivo in RV outflow tract samples from 22 TOF and three ASD patients. Arrhythmias were provoked by superfusion with solutions containing reduced potassium and barium chloride, or isoprenaline. Myocardial fibrosis was quantified histologically and associations between clinical phenotype, AP shape, tissue arrhythmia propensity, and fibrosis were examined.

RESULTS

Electrophysiological abnormalities (arrhythmias, AP duration [APD] alternans, impaired APD shortening at increased stimulation frequencies) were generally present in TOF tissue, even from infants, but rare or absent in ASD samples. More severely diseased and acyanotic patients, pronounced tissue susceptibility to arrhythmogenesis, and greater fibrosis extent were associated with longer APD. In contrast, APD was shorter in tissue from patients with pre-operative cyanosis. Increased fibrosis and repaired-TOF status were linked to tissue arrhythmia inducibility.

CONCLUSIONS

Functional and structural tissue remodelling may explain arrhythmic activity in TOF patients, even at a very young age. Surprisingly, clinical acyanosis appears to be associated with more severe arrhythmogenic remodelling. Further research into the clinical drivers of structural and electrical myocardial alterations, and the relation between them, is needed to identify predictive factors for patients at risk.

Advancements in the diagnosis and management of premature ventricular contractions in pediatric patients

Background

Premature ventricular contractions (PVCs) are relatively common arrhythmias in the pediatric population, with implications that range from benign to potentially life-threatening. The management of PVCs in children poses unique challenges, and recent advancements in diagnostic and therapeutic options call for a comprehensive review of current practices.

Methods

This review synthesizes the latest literature on pediatric PVCs, focusing on publications from the past decade. We evaluate studies addressing the epidemiology, pathophysiology, diagnosis, and treatment of PVCs in children, including pharmacological, non-pharmacological, and invasive strategies.

Results

The review identifies key advancements in the non-invasive detection of PVCs, the growing understanding of their genetic underpinnings, and the evolving landscape of management options. We discuss the clinical decision-making process, considering the variable significance of PVCs in different pediatric patient subgroups, and highlight the importance of individualized care. Current guidelines and consensus statements are examined, and areas of controversy or limited evidence are identified.

Conclusions

Our review underscores the need for a nuanced approach to PVCs in children, integrating the latest diagnostic techniques with a tailored therapeutic strategy. We call for further research into long-term outcomes and the development of risk stratification tools to guide treatment. The potential of emerging technologies and the importance of multidisciplinary care are also emphasized to improve prognoses for pediatric patients with PVCs.

High-density electroanatomic mapping with grid catheter in pediatrics and congenital heart disease

BACKGROUND

The Advisor™ HD Grid mapping catheter (Abbott Laboratories; Chicago, IL) allows for bipolar electrogram collection in both orthogonal and perpendicular planes, unique when compared to traditional and branch catheters. Experience in pediatric patients and congenital heart disease (CHD) is limited. The purpose of this work was to evaluate the utility and safety of the Advisor™ HD Grid mapping catheter in pediatric and CHD populations.

METHODS

Retrospective review of all pediatric patients and those with CHD (regardless of age) at Children's Hospital Colorado and University of Colorado undergoing electrophysiologic study in which the Advisor™ HD Grid mapping catheter was utilized.

RESULTS

Sixty-five procedures in 60 patients (N = 31 female (47.6%), median age 17 years (15-24.1)) were included. Patients had CHD in 30 procedures (46.1%). Eight-eight arrhythmia substrates were mapped including atrial flutter/intra-atrial reentrant tachycardia (N = 33), focal atrial tachycardia (N = 20), isolated PVCs (N = 10), accessory pathways (N = 9), atrioventricular nodal reentrant tachycardia (N = 7), right ventricular substrate mapping (N = 7), and ventricular tachycardia (N = 2). Median time per map was 11.8 (7.5-20.1) min with 3.2 (± 1.7) maps per procedure and a median of 2634 (1767-7654) points used per map. Patients with CHD required more maps (p < 0.001) and points per map (p < 0.001). Ablation was successful in 92.4% of procedures.

CONCLUSIONS

The Advisor™ HD Grid mapping catheter is safe and effective in the pediatric and congenital heart disease population. A wide variety of arrhythmia substrates can be mapped with high point density and low mapping time.

Tachyarrhythmias in Congenital Heart Diseases: From Ion Channels to Catheter Ablation

Major advances in pediatric cardiology in recent decades, especially surgical techniques, have resulted in an increasing number of patients with congenital heart disease (CHD) surviving to adulthood. This has generated new challenges, particularly with regards to the late onset of complex arrhythmias. Abnormal anatomy, surgical scarring, chronic hypoxemia, hemodynamic compromise, neuro-hormonal abnormalities, and genetic factors can all contribute to creating a unique substrate for arrhythmia development. This review attempts to synthesize the current state of knowledge spanning the spectrum from underlying mechanisms of arrhythmias in patients with congenital heart disease to current ablative strategies. We discuss existing knowledge gaps and highlight important areas for future research.

Ventricular Arrhythmias and Sudden Death Following Percutaneous Pulmonary Valve Implantation in Pediatric Patients

Reports have suggested a transient increase in ventricular ectopy early after percutaneous pulmonary valve implantation (PPVI). Little is known about the potential for more serious ventricular arrhythmias (VA) in children who undergo PPVI. We sought to evaluate the incidence of severe VA following PPVI in a pediatric population and to explore potential predictive factors. A retrospective cohort study was conducted of patients who underwent PPVI under 20 years of age in our institution from January 2007 to December 2019. The primary outcome of severe VA was defined as sustained and/or hemodynamically unstable ventricular tachycardia (VT), inducible sustained VT, or sudden death of presumed arrhythmic etiology. A total of 21 patients (mean age 16.2 ± 2.1 years; 66.7% male) underwent PPVI. The majority of patients (N = 15; 71.4%) had tetralogy of Fallot (TOF) or TOF-like physiology, with the most common indication being pulmonary insufficiency (N = 10; 47.6%). During a median follow-up of 29.6 months (IQR 10.9-44.0), severe VA occurred in 3 (14.3%) patients aged 15.6 (IQR 14.7-16.1) a median of 12.3 months (IQR 11.2-22.3) after PPVI. All events occurred in patients with TOF-like physiology following Melody valve implant. In conclusion, severe VA can occur long after PPVI in a pediatric population, particularly in those with TOF-like physiology. Further studies are required to elucidate underlying mechanisms and assess strategies to mitigate risks.

Mechanism of ventricular tachycardia in a patient with double-outlet left ventricle

We report the case of ventricular tachycardia (VT) ablation procedure in a patient with history of surgically repaired double-outlet left ventricle. The electrophysiology procedure revealed a re-entry pattern between the right-ventricle to main-pulmonary-artery conduit and the tricuspid annulus. The re-entrant mechanism was most likely promoted by a fibrous remodeling of this area, related to the surgical repair. This case is the first to describe a re-entry mechanism between fixed anatomical barriers in a repaired right ventricle of a double-outlet left ventricle. A pace mapping technique was used to highlight the VT isthmus.

Narrative review of: risk stratification and implantable cardioverter-defibrillator therapy in adults with congenital heart disease

Fortunately, the population of adults with congenital heart disease (ACHD) is growing due to improved operation techniques. Life expectancy is continuously rising, nevertheless, sudden cardiac death is one of the leading causes of mortality in ACHD late after initial diagnosis. Risk stratification in ACHD remains challenging as large study results are missing, congenital defects and operation methods differ considerably between individual patients and results from acquired heart diseases are often not conferrable. The purpose of this narrative review is to objectively summarize the current knowledge on arrhythmogenic risk of ACHD and to give an overview on implantable cardioverter-defibrillator (ICD) therapy in this collective. Remarkable progress has been made in electrophysiological understanding of critical areas of slow conduction especially in patients with Tetralogy of Fallot (ToF). In patients with transposition of the great arteries after atrial baffling (Mustard/Senning procedure) atrial arrhythmias play a crucial role in sudden cardiac death. ICD therapy in ACHD may pose special technical challenges due to limited access for intracardiac leads. The introduction of the totally subcutaneous ICD improved therapeutic options for ACHD especially when contraindications for transvenous leads are present. Risk stratification in ACHD has to be seen as a team approach, requires thorough understanding of congenital heart defects and the operation techniques and needs unconventional technical approaches in some cases.

Therapy of supraventricular and ventricular arrhythmias in adults with congenital heart disease-narrative review

Arrhythmias are among the most common late complications in adults with congenital heart disease (ACHD) and a frequent reason for hospital admission. Both, supraventricular and ventricular arrhythmias, not only cause debilitating symptoms, but may be life-threatening by increasing risk of stroke, causing or worsening heart failure and being associated with sudden death. Substrate and risk for arrhythmia differs widely between congenital defects with specific arrhythmias being much more common in some patients than others. Atrial macroreentrant arrhythmias are particularly frequent in patients with atrial septal defects and repair that involves atrial incisions including patients with transposition of the great arteries (TGA) and atrial switch. Accessory pathways and related arrhythmias are often associated with Ebstein's anomaly and congenitally corrected TGA. Monomorphic ventricular arrhythmias occur in patients with ventricular incisions, namely patients with Tetralogy of Fallot. Changes in surgical repair techniques influence arrhythmia prevalence and substrate as well as anatomical access for catheter ablation procedures. In addition, epidemiologic changes associated with improved long-term survival will further increase the prevalence of atrial fibrillation in ACHD. This article summarizes current understanding of prevalence of specific arrhythmias, underlying mechanisms, medical and interventional treatment options and their outcome in ACHD.

The Role of Ablation in Prevention of Recurrent Implantable Cardioverter Defibrillator Shocks in Patients With Tetralogy of Fallot

Background

Implantable cardioverter defibrillators (ICDs) are effective in preventing arrhythmic sudden cardiac death in patients with tetralogy of Fallot (TOF). Although ICD therapies for malignant ventricular arrhythmias can be life-saving, shocks could have deleterious consequences. Substrate-based ablation therapy has become the standard of care to prevent recurrent ICD shocks in patients with ischemic cardiomyopathy. However, the efficacy and safety of this invasive therapy in the prevention of recurrent ICD shocks in patients with TOF has not been well evaluated.

Methods

Records of a total of 47 consecutive TOF patients (mean age: 43.1 ± 13.2 years, male sex: n = 34 [72.3%]) who underwent ICD implantation for secondary prevention between 2000 and 2018 were reviewed.

Results

Twenty (42.6%) patients underwent invasive therapy (radiofrequency catheter ablation, n = 8; surgical ablation with pulmonary valve replacement, n = 12) before ICD implantation. Twenty-seven patients (57.4%) were managed noninvasively. During follow-up (median 80.5 [interquartile range, 28.5-131.0] months), 2 (10.0%) patients in the invasive group and 10 (37.0%) patients in the noninvasive group received appropriate ICD shocks (P = 0.036). Logistic regression analysis showed that invasive therapy was associated with a decreased risk of ICD shocks by 81.1% (odds ratio, 0.189; 95% confidence interval, 0.036-0.990; P = 0.049). Furthermore, invasive therapy was associated with decreased risk of the composite outcomes of ICD shock, death, cardiac transplantation, and hospital admission (odds ratio, 0.090; 95% confidence interval, 0.025-0.365; P = 0.013) compared with noninvasive therapy.

Conclusions

Invasive substrate modification therapy was associated with a lower likelihood of ICD shocks and improvement of long-term outcomes in TOF patients.

Focal scar and diffuse myocardial fibrosis are independent imaging markers in repaired tetralogy of Fallot

Aims

To identify the correlates of focal scar and diffuse fibrosis in patients with history of tetralogy of Fallot (TOF) repair.

Methods and results

Consecutive patients with prior TOF repair underwent electrocardiogram, 24-h Holter, transthoracic echocardiography, exercise testing, and cardiac magnetic resonance (CMR) including cine imaging to assess ventricular volumes and ejection fraction, T1 mapping to assess left ventricular (LV) and right ventricular (RV) diffuse fibrosis, and free-breathing late gadolinium-enhanced imaging to quantify scar area at high spatial resolution. Structural imaging data were related to clinical characteristics and functional imaging markers. Cine and T1 mapping results were compared with 40 age- and sex-matched controls. One hundred and three patients were enrolled (age 28 ± 15 years, 36% women), including 36 with prior pulmonary valve replacement (PVR). Compared with controls, TOF showed lower LV ejection fraction (LVEF) and RV ejection fraction (RVEF), and higher RV volume, RV wall thickness, and native T1 and extracellular volume values on both ventricles. In TOF, scar area related to LVEF and RVEF, while LV and RV native T1 related to RV dilatation. On multivariable analysis, scar area and LV native T1 were independent correlates of ventricular arrhythmia, while RVEF was not. Patients with history of PVR showed larger scars on RV outflow tract but shorter LV and RV native T1.

Conclusion

Focal scar and biventricular diffuse fibrosis can be characterized on CMR after TOF repair. Scar size relates to systolic dysfunction, and diffuse fibrosis to RV dilatation. Both independently relate to ventricular arrhythmias. The finding of shorter T1 after PVR suggests that diffuse fibrosis may reverse with therapy.

Re-entrant ventricular tachycardia in a postoperative case of tetralogy of Fallot - Ablated successfully under the three-dimensional mapping system

A 47-year-old female underwent cardiac repair for tetralogy of Fallot at the age of 12 years. Subsequently, she was asymptomatic on follow-up. Recently, she presented elsewhere with palpitations and presyncope with documented ventricular tachycardia (VT) having left bundle branch block morphology with inferior QRS axis and late precordial transition. She was reported to have cardioverted and referred to our center for electrophysiology study (EP). She underwent EP study which induced clinical VT which was hemodynamically stable and the mechanism of VT was confirmed as re-entry. With the help of three-dimensional mapping system, VT circuit was identified in the posterior right ventricular outflow tract region between the pulmonary valve and upper end of ventricular septal defect patch. Delivery of radiofrequency energy during VT terminated the tachycardia with no further inducible VT despite aggressive pacing protocols.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias: Executive summary

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Value of Cardiovascular Magnetic Resonance Imaging in Noninvasive Risk Stratification in Tetralogy of Fallot

Importance

Adults late after total correction of tetralogy of Fallot (TOF) are at risk for major complications. Cardiovascular magnetic resonance (CMR) imaging is recommended to quantify right ventricular (RV) and left ventricular (LV) function. However, a commonly used risk model by Khairy et al requires invasive investigations and lacks CMR imaging to identify high-risk patients.

Objective

To implement CMR imaging in noninvasive risk stratification to predict major adverse clinical outcomes.

Design, Setting, and Participants

This multicenter study included 575 adult patients with TOF (4.083 patient-years at risk) from a prospective nationwide registry in whom CMR was performed. This study involved 5 tertiary referral centers with a specialized adult congenital heart disease unit. Multivariable Cox hazards regression analysis was performed to determine factors associated with the primary end point. The CMR variables were combined with the noninvasive components of the Khairy et al risk model, and the C statistic of the final noninvasive risk model was determined using bootstrap sampling. The data analysis was conducted from January to December 2016.

Main Outcomes and Measures

The composite primary outcome was defined as all-cause mortality or ventricular arrhythmia, defined as aborted cardiac arrest or documented ventricular fibrillation and ventricular tachycardia (lasting ≥30 seconds or recurrent symptomatic).

Results

Of the 575 patients with TOF, 57% were male, and the mean (SD) age was 31 (11) years. During a mean (SD) follow-up of 7.1 (3.5) years, the primary composite end point occurred in 35 patients, including all-cause mortality in 13 patients. Mean (SD) RV ejection fraction (EF) was 44% (10%), and mean (SD) LV EF was 53% (8%). There was a correlation between RV EF and LV EF (R, 0.36; 95% CI, 0.29-0.44; P < .001). Optimal thresholds for ventricular function (RV EF <30%: hazard ratio, 3.90; 95% CI, 1.84-8.26; P < .001 and LV EF <45%: hazard ratio, 3.23; 95% CI, 1.57-6.65; P = .001) were independently predictive in multivariable analysis. Both thresholds were included in a point-based noninvasive risk model (C statistic, 0.75; 95% CI, 0.63-0.85) and combined with the noninvasive components of the Khairy et al risk model.

Conclusions and Relevance

In patients with repaired TOF, biventricular dysfunction on CMR imaging was associated with major adverse clinical outcomes. The quantified thresholds (RV EF <30% and LV EF <45%) may be implemented in noninvasive risk stratification.

Successful Treatment of Ventricular Arrhythmia in Tetralogy of Fallot Repair Using Catheter Ablation

Tetralogy of Fallot (ToF) is one of the most prevalent congenital heart disease. Its surgical corrections may haemodinamically correct a disease, but the incisions may create scars that will originate ventricular arrhythmias. Even though life threatening arrhythmias are not common, some patients present unstable ventricular tachycardia (VT) of ectopic ventricular beats triggering heart failure and symptoms. We describe the treatment of a 16-years-old woman with late ToF repair and drug refractory Implantable cardioverter defibrillator (ICD) shocks. The patient underwent successful ablation of VT using X-ray and anatomic landmarks without the use of electroanatomical mapping. We were able to reduce drugs after one month of ablation and improve quality of life and symptoms. In this paper we describe the indications and perform a brief review of the key points for successful radiofrequency catheter ablation of VT in ToF patients.

Point catheter ablation of macro-re-entrant ventricular tachycardia in a patient after surgical repair for double-outlet right ventricle

Catheter ablation of ventricular tachycardia is often difficult in patients after surgery for CHD. In patients with a ventricular septal defect patch, it is necessary to decide which ventricular side is appropriate for catheter ablation. In this article, we report a case of successful point catheter ablation of re-entrant ventricular tachycardia. Identification of the ventricular septal defect patch using intra-cardiac echocardiography was useful.

Ablation of Ventricular Tachycardia in Congenital and Infiltrative Heart Disease

Radiofrequency catheter ablation (RFCA) is an important treatment modality to prevent ventricular tachycardia (VT) recurrence in patients with repaired congenital heart disease. Identification and ablation of anatomic isthmuses has improved acute ablation outcome with excellent VT-free survival in those with preserved biventricular function. Reports on RFCA for VT in patients with infiltrative disease are sparse and cardiac sarcoidosis seems to be the most prevalent cause for ventricular arrhythmia. Patients with active and ongoing inflammation are at high risk for VT recurrence. RFCA reduces the number of VT but often multiple procedures are required and long-term VT-free survival is unfavorable in those with left ventricular dysfunction.

Ventricular arrhythmias and sudden death in tetralogy of Fallot

Malignant ventricular arrhythmias and sudden cardiac death may late happen in repaired tetralogy of Fallot, although probably less frequently than previously thought, especially with the advent of new surgical techniques/management. Ventricular tachycardias are caused by reentry around the surgical scars/patches and valves. Many predictive factors have been proposed, which suffer from poor accuracy. There is currently no recommended indication for prophylactic implantable cardioverter defibrillator implantation-except maybe in the case of multiple risk factors-while radiofrequncy ablation may be proposed in secondary prevention with or even without a back-up implantable cardioverter defibrillator in selected cases. Repeated cardiological investigations and monitoring should be proposed for every operated patient.

Ventricular Tachycardia Ablation Clinical Trials

Catheter ablation is an increasingly used treatment option for patients with ventricular tachycardia (VT) in the setting of structural heart disease. Although there are extensive data from several retrospective studies as well as prospective nonrandomized observational studies, there are limited data from relatively few randomized controlled trials, especially comparing VT ablation with antiarrhythmic drugs. In this review, the authors aim to summarize the major studies examining efficacy of VT ablation in patients with structural heart disease, discuss barriers to enrollment and completion of randomized clinical trials, and propose areas of future research in the field.