His Bundle and Left Bundle Pacing in Pediatrics and Congenital Heart Disease: A Single Center Experience

Interventional Cardiac Electrophysiology for the Management of Adults With Congenital Heart Disease

Congenital heart disease (CHD) is the most common congenital anomaly in newborns. Advances in catheter and surgical techniques led to the majority of these patients surviving into adulthood, leading to evolving challenges due to the emergence of long-term complications such as arrhythmias. Interventional electrophysiology (EP) has had remarkable advances over the last few decades, and various techniques and devices have been explored to treat adult patients with CHD. This comprehensive review aims to summarize findings from recent studies exploring advances in the use of interventional electrophysiology to manage adult patients with CHD. While pacemaker therapy has some indications in adults with CHD, various long-term consequences include pacing-induced cardiomyopathy and complications requiring reintervention. Cardiac resynchronization therapy has shown promising results in some studies to treat CHD patients with heart failure, although further research to clarify guidelines is encouraged. Implantable cardiac defibrillators have demonstrated clear benefits in CHD patients and are indicated for primary prevention of sudden cardiac death, although selection criteria for secondary prevention of sudden cardiac death are uncertain. Catheter ablation has also been used for various atrial and ventricular arrhythmias in patients with CHD with high success rates, although the likelihood of success depends on patient characteristics and the type of arrhythmia, and multidisciplinary assessment is encouraged to improve the chance of successful therapy.

Conduction System Pacing in Children and Congenital Heart Disease

Permanent cardiac pacing in children with congenital complete atrioventricular block (CCAVB) and/or congenital heart disease (CHD) is challenging. Conduction system pacing (CSP) represents a novel pacing strategy aiming to preserve physiological ventricular activation. Patients with CCAVB or CHD are at high risk of developing pacing-induced cardiomyopathy with chronic conventional right ventricular myocardial pacing. CSP may be a valuable pacing modality in this particular setting because it can preserve ventricular synchrony. In this review, we summarise implantation techniques, the available clinical evidence and future directions related to CSP in CCAVB and CHD.

Conduction System Pacing in Pediatrics and Congenital Heart Disease, a Single Center Series of 24 Patients

His-bundle pacing has demonstrated feasibility in numerous adult studies to reverse and prevent pacing-induced cardiomyopathy, however, is met with higher capture thresholds with deployment sheaths designed for adults with his-bundles in the typical location. To describe 24 pediatric and adult congenital patients post-physiologic pacing. Patients at the University of Minnesota Masonic Children's Hospital with congenital complete heart block or congenital heart disease and atrioventricular block presented for pacemaker placement between November 2019 and January 2021. Twenty-four patients had attempted his-bundle placement using either Medtronic's C315 or C308 sheaths and 3830 leads except for 3 patients who had Boston Scientific's His system with the Shape 3 sheath and 7842 leads. Twenty-four total patients underwent physiologic pacing (23 his-bundle, 13 female, 11 male) with median age of 14 years (range 8-39 years) with median weight of 51 kg (range 21.2-81 kg) with five right-sided implants performed. Twelve patients had congenital heart disease including atrioventricular canal defects, tetralogy of Fallot, and ventricular septal defect repairs (nine patients with ventricular septal defect repairs). Twelve patients had selective His-bundle pacing (six with congenital heart disease). Median threshold to capture was 0.5 V at 0.4 ms (range 0.4 to 1.1 V at 0.4 ms), impedance 570 ohms (range 456-1140 ohms), and sensing median of 9.7 mV (range 1.5-13.8 mV if present). The median follow-up time was 610 days (range 240-760 days). No complications occurred peri-procedurally or during follow-up. His-bundle pacing is feasible in pediatric and congenital heart disease patients.

Longitudinal echocardiographic parameters before and after pacemaker placement in congenital complete heart block

BACKGROUND

Congenital complete heart block (CCHB) is seen in 1:15,000-1:20,000 live births, with risk of left ventricular (LV) dysfunction or dilated cardiomyopathy in 7%-23% of subjects.

OBJECTIVE

The purpose of this study was to investigate serial changes in LV size and systolic function in paced CCHB subjects to examine the effect of time from pacemaker on echocardiographic parameters.

METHODS

Single-center retrospective cohort analysis of paced CCHB subjects was performed. Echocardiographic data were collected before and after pacemaker placement. Linear mixed effect regression of left ventricular end-diastolic dimension (LVEDD) z-score, left ventricular shortening fraction (LVSF), and left ventricular ejection fraction (LVEF) was performed, with slopes compared before and after pacemaker placement.

RESULTS

Of 114 CCHB subjects, 52 had echocardiographic data before and after pacemaker placement. Median age at CCHB diagnosis was 0.6 [interquartile range 0.0-3.5] years; age at pacemaker placement 3.4 [0.5-9.0] years; and pacing duration 10.8 [5.2-13.7] years. Estimated LVEDD z-score was 1.4 at pacemaker placement and decreased -0.08 per year (95% confidence interval [CI] -0.12 to -0.04; P = .002) to 0.2 (95% CI -0.3 to +0.3) 15 years postplacement. Estimated LVSF decreased -1.1% per year (95% CI -1.7% to -0.6%; P <.001) from 6 months prepacemaker placement to 34% (95% CI 32%-37%) 4 years postplacement. There was no significant change in LVSF between 4 and 15 years postplacement. Estimated LVEF did not change significantly after pacemaker placement, with estimated LVEF 59% (95% CI 55%-62%) 15 years postplacement.

CONCLUSION

In 52 paced CCHB subjects, estimated LVEDD z-score decreased significantly after pacemaker placement, and estimated LVSF and LVEF remained within normal limits at 15 years postpacemaker placement.

A Study to Analyse the Feasibility and Effectiveness of Left Bundle Branch Area Pacing Used in Young Children

This study aimed to investigate the feasibility and effectiveness of left bundle branch area pacing (LBBaP) in young children. From September 2020 to May 2021, a total of 31 children (≤ 7 years) with complete atrioventricular block were included. All patients were scheduled to undergo LBBaP. Pacing parameters, and cardiac function and synchrony were evaluated during follow-up. LBBaP succeeded in 21 children (3.3 ± 2.1 years old), with a success rate of 70.9%. LBBaP failed in nine children, who eventually received right ventricular septal pacing (RVSP). The average postoperative QRS duration in patients of LBBaP group was narrower than that of RVSP group: 100.9 ± 9.1 versus 114.2 ± 11.9 ms (P = 0.002). The median follow-up duration was 12 [interquartile range (IQR) 6-15] months. At last time of follow-up, the capture threshold of ventricular electrode in patients of LBBaP group were significantly lower than that of RVSP group (0.70 ± 0.25 versus 1.39 ± 0.94 V, P = 0.011). The echo-left ventricular ejection fraction (LVEF) in patients in the LBBaP group was better than that in the RVSP group (66.1 ± 3.3 versus 63.1 ± 2.2%, P = 0.025). LBBaP can be safely and effectively administered in young children. Satisfactory pacing parameters, and narrow QRS durations were obtained.

Conduction System Pacing in Pediatrics and Congenital Heart Disease: A Case Report and Literature Review

Conduction system pacing involving either His bundle pacing (HBP) or left bundle branch pacing (LBBP) is a modality that has been introduced as a safe and effective alternative to right ventricular (RV) pacing to help prevent pacemaker-associated cardiomyopathy. While HBP has been employed in the pediatric and congenital populations, several small studies have shown LBBP to be safe and effective in the pediatric population. We present a patient with congenital atrioventricular block and postoperative ventricular septal defect repair cardiomyopathy with subsequent left ventricular function improvement following a transition from an RV epicardial pacemaker system to an LBBP system. This case report serves as a foundation for a review of the current state of LBBP in pediatrics and congenital heart disease.

Lead Management in Patients with Congenital Heart Disease

Pediatric patients with congenital heart disease present unique challenges when it comes to cardiac implantable electronic devices. Pacing strategy is often determined by patient size/weight and operator experience. Anatomic considerations, including residual shunts, anatomic obstructions and barriers, and abnormalities in the native conduction system, will affect the type of CIED implanted. Given the young age of patients, it is important to have an "eye on the future" when making pacemaker/defibrillator decisions, as one can expect several generator changes, lead revisions, and potential lead extractions during their lifetime.

Conduction System Pacing for Patients with Congenital Heart Disease

For patients with congenital heart disease (CHD), chronic ventricular pacing may lead to progressive cardiomyopathy owing to electromechanical dyssynchrony. Cardiac conduction system pacing (CSP) has been proposed as a physiologic pacing strategy-directly engaging the His-Purkinje system and preserving electromechanical synchrony. CSP may be indicated for a wide variety of children and adults with CHD and has emerged as an important tool in the armamentarium for cardiac implantable electronic device operators. This review provides the rationale, background, and supportive evidence for CSP in patients with CHD and discusses implant strategies and outcomes in the context of dominant ventricular morphologic categories.

Comparison of ventricular synchrony in children with left bundle branch area pacing and right ventricular septal pacing

OBJECTIVE

This study aimed to determine the ideal pacing site in children by comparing the postoperative ventricular synchrony in children with left bundle branch area pacing and those with right ventricular septal pacing.

METHODS

This retrospective study included children with complete atrioventricular block who underwent permanent pacemaker implantation from March 2019 to August 2021. Patients were grouped according to their ventricular pacing site, the left bundle branch area pacing group and the right ventricular septal pacing group. Two-dimensional speckle tracking echocardiography was used to evaluate the ventricular synchrony.

RESULTS

Forty-eight children (median age, 2.7 years; interquartile range, 1.7-4.6 years) were included. The paced QRS duration in the left bundle branch area pacing group was significantly narrower than that in the right ventricular septal pacing group (100.2 ± 9.3 versus 115.4 ± 15.1 ms, p = 0.001). The median follow-up duration was 1.5 years (interquartile range, 1-2 years). At the last follow-up, the average capture threshold of the ventricular electrode in the left bundle branch area pacing group was lower than that in the right ventricular septal pacing group (0.79 ± 0.18 versus 1.20 ± 0.56 V, p = 0.008). The left ventricular intraventricular synchrony parameters in the left bundle branch area pacing group were better than those in the right ventricular septal pacing group (e.g. standard deviation of the time to peak longitudinal strain, 37.4 ± 4.3 versus 46.6 ± 8.2 ms, p = 0.000). The average interventricular mechanical delay time in the left bundle branch area pacing group was significantly shorter than that in the right ventricular septal pacing group (36.4 ± 14.2 versus 52.5 ± 22.7 ms, p = 0.016).

CONCLUSION

Compared with right ventricular septal pacing, left bundle branch area pacing in children produces a narrower QRS duration and better pacing and ventricular synchrony parameters postoperatively.

Left ventricular endocardial activation maps during right ventricular pacing in pediatric patients

BACKGROUND

Cardiac pacing from right ventricular (RV) sites may cause electromechanical ventricular dyssynchrony. Invasive and noninvasive mapping studies showed left ventricular (LV) activation sequence in adults. Aim of this study was to seek out the LV endocardial activation (LVEA) in pediatric patients who underwent RV pacing.

METHODS

Single-center, prospective study conducted on pediatric patients who underwent left sided catheter ablation of accessory pathways with the Carto Univu mapping system. After successful ablation procedures, LVEA was recorded by the ablation catheter during sinus rhythm (SR) and during para-hisian (PHP), midseptum (MSP), and apical (RVAP) pacing.

RESULTS

Seventeen patients, 13 males, aged 12 (10-15) years, registered LV activation maps and times (LVAT). SR showed significantly shorter LVAT than during pacing. LVAT of PHP was shorter than MSP, while there were not significant differences among PHP and MSP versus RVAP. In SR initial LV endocardial activation occurred in two midseptum sites, inferior-posterior and superior-anterior. During PHP, initial activation occurred at parahisian basal septum, rapidly followed by midseptum as in SR. During MSP and RVAP initial activation occurred at midseptum and apex, respectively. From all initial sites, the excitation spreads toward the base of the lateral LV free wall. A mild linear correlation was found between QRS duration and LVAT for MSP and for PHP.

CONCLUSIONS

In pediatric patients LVEA maps during RV pacing showed that the shortest LVAT was obtained with PHP. The LV activation pattern seemed similar in sinus rhythm, PHP and MSP, from midseptum to LV lateral base.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

Case report: Challenges and implications of conduction system pacing in pediatrics: Case series

Cardiac electrical stimulation in children usually is needed in the setting of complete congenital atrioventricular block, atrioventricular block after heart surgery, and bradycardia associated with some specific channelopathies. In cases of atrioventricular block, the high percentage of ventricular stimulation raises concern on the deleterious effects of chronic stimulation of the right ventricle. In recent years, physiologic stimulation has developed as a valid approach for adult patients and a great interest has risen in offering conduction system pacing also to the pediatric population. We present three pediatric cases of stimulation of the conduction system (His bundle or left bundle branch), in order to show the intrinsic particularities and challenges implied in these new techniques.

Left bundle branch area pacing in congenital heart disease

AIMS

Left bundle branch area pacing (LBBAP) has been shown to be effective and safe. Limited data are available on LBBAP in the congenital heart disease (CHD) population. This study aims to describe the feasibility and safety of LBBAP in CHD patients compared with non-CHD patients.

METHODS AND RESULTS

This is a single-centre, non-randomized observational study recruiting consecutive patients with bradycardia indication. Demographic data, ECGs, imaging, and procedural data including lead parameters were recorded. A total of 39 patients were included: CHD group (n = 13) and non-CHD group (n = 26). Congenital heart disease patients were younger (55 ± 14.5 years vs. 73.2 ± 13.1, P < 0.001). Acute success was achieved in all CHD patients and 96% (25/26) of non-CHD patients. No complications were encountered in either group. The procedural time for CHD patients was comparable (96.4 ± 54 vs. 82.1 ± 37.9 min, P = 0.356). Sheath reshaping was required in 7 of 13 CHD patients but only in 1 of 26 non-CHD patients, reflecting the complex and distorted anatomy of the patients in this group. Lead parameters were similar in both groups; R wave (11 ± 7 mV vs. 11.5 ± 7.5, P = 0.881) and pacing threshold (0.6 ± 0.3 V vs. 0.7 ± 0.3, P = 0.392). Baseline QRS duration was longer in the CHD group (150 ± 28.2 vs. 118.6 ± 26.6 ms, P = 0.002). Despite a numerically greater reduction in QRS and a similar left ventricular activation time (65.9 ± 6.2 vs. 67 ± 16.8 ms, P = 0.840), the QRS remained longer in the CHD group (135.5 ± 22.4 vs. 106.9 ± 24.7 ms, P = 0.005).

CONCLUSION

Left bundle branch area pacing is feasible and safe in CHD patients as compared to that in non-CHD patients. Procedural and fluoroscopy times did not differ between both groups. Lead parameters were satisfactory and stable over a short-term follow-up.

Conduction System Pacing Versus Conventional Cardiac Resynchronization Therapy in Congenital Heart Disease

BACKGROUND

Dyssynchrony-associated left ventricular systolic dysfunction is a major contributor to heart failure in congenital heart disease (CHD). Although conventional cardiac resynchronization therapy (CRT) has shown benefit, the comparative efficacy of cardiac conduction system pacing (CSP) is unknown.

OBJECTIVES

To compare the clinical outcomes of CSP vs conventional CRT in CHD with biventricular, systemic left ventricular anatomy.

METHODS

Retrospective CSP data from 7 centers were compared with propensity score-matched conventional CRT control subjects. Outcomes were lead performance, change in left ventricular ejection fraction (LVEF), and QRS duration at 12 months.

RESULTS

A total of 65 CSP cases were identified (mean age 37 ± 21 years, 46% men). The most common CHDs were tetralogy of Fallot (n = 12 [19%]) and ventricular septal defect (n = 12 [19%]). CSP was achieved after a mean of 2.5 ± 1.6 attempts per procedure (38 patients with left bundle branch pacing, 17 with HBP, 10 with left ventricular septal myocardial). Left bundle branch area pacing [LBBAP] vs HBP was associated with a smaller increase in pacing threshold (Δ pacing threshold 0.2 V vs 0.8 V; P = 0.05) and similar sensing parameters at follow-up. For 25 CSP cases and control subjects with baseline left ventricular systolic dysfunction, improvement in LVEF was non-inferior (Δ LVEF 9.0% vs 6.0%; P = 0.3; 95% confidence limits: -2.9% to 10.0%) and narrowing of QRS duration was more pronounced for CSP (Δ QRS duration 35 ms vs 14 ms; P = 0.04). Complications were similar (3 [12%] CSP, 4 [16%] conventional CRT; P = 1.00).

CONCLUSIONS

CSP can be reliably achieved in biventricular, systemic left ventricular CHD patients with similar improvement in LVEF and greater QRS narrowing for CSP vs conventional CRT at 1 year. Among CSP patients, pacing electrical parameters were superior for LBBAP vs HBP.

The history of cardiac pacing in the young and a look to the future

PURPOSE OF REVIEW

The purpose of this review is to explore the historical and serendipitous events that led to the creation of modern-day pacemakers. In addition, this review will explore how contemporary conduction site-specific pacing has overcome some of the deleterious effects from historical chronic right ventricular apical pacing.

RECENT FINDINGS

Recently, there have been tremendous advances in not just the lead design but the tools required to promote more physiologic pacing. Although cardiac resynchronization pacing has been around for nearly 2 decades, this review also introduces and discusses the early results of His-bundle pacing and left bundle branch pacing and some of the potential applicability of this technology for our children.

SUMMARY

Pacemakers have evolved significantly in the last 30 years through collaborative partnerships between physicians and engineers. The future of cardiac pacing is bright compared to the field of electrotherapy 50 years ago. Future iterations of pacemakers must consider unusual anatomy and growing children. Pediatric patients contribute to a small percentage of the overall device volume, but the majority of these patients will have a pacemaker for life. We need to be proactive and consider what are the best short and long-term solutions for this cohort.

Preliminary study on left bundle branch area pacing in children:clinical observation of 12 cases

OBJECTIVE

To explore the safety and feasibility of left bundle branch area pacing (LBBAP) in children.

METHODS

This study observed 12 children attempted LBBAP from January 2019 to January 2021 in the department of pediatric cardiology of Anzhen Hospital prospectively.Clinical data, pacing parameters, electrocardiograms, intracardiac electrograms, echocardiographic measurements and complications were recorded at implant and during follow-up.

RESULTS

The 12 patients aged between 3 and 14 years old and weighted from 13 to 48kg. Eleven patients were diagnosed with third-degree atrioventricular block and 1 patient (case 4) suffered from cardiac dysfunction due to right ventricular apical pacing (RVAP). Left bundle branch area pacing was successfully achieved in all patients with narrow QRS complexes and V₁ lead showed changes like right bundle branch block in the pacing electrocardiogram. Left ventricular ejection fraction in case 4 recovered on the 3rd day after LBBAP. The median of left ventricular end diastolic diameter Z score of the 12 patients decreased from 1.75 to1.05 3 months after implantation (p<0.05). The median of paced QRS duration was 103ms. The median of pacing threshold, R-wave amplitude and impedance were 0.85V, 15mV and 717Ω respectively and remained stable during follow-up. No complications such as loss of capture, lead dislodgement or septal perforation occurred.

CONCLUSIONS

Left bundle branch area pacing can be performed safely in children with narrow QRS duration and stable pacing parameters. Cardiac dysfunction caused by long-term RVAP can be corrected by LBBAP quickly. This article is protected by copyright. All rights reserved.

Incidence of Morbidity and Mortality in a Cohort of Congenital Complete Heart Block Patients Followed Over 40 Years

BACKGROUND

Congenital Complete Heart Block (CCHB), seen in 1:15,000-20,000 births, commonly requires pacemaker placement by young adulthood. There is limited understanding of cardiac morbidity and mortality.

OBJECTIVE

Determine long-term incidence of cardiac morbidity and mortality in subjects with CCHB and identify associated risk factors.

METHODS

Retrospective cohort analysis of subjects with CCHB at Children's Hospital of Philadelphia between 1976-2018. The primary outcome is a composite of death, left ventricular systolic dysfunction, heart failure, cardiomyopathy, or cardiac resynchronization therapy (CRT). Cox proportional hazard models assessed independent risk factors for the primary outcome and its components (death, heart failure and/or cardiomyopathy, CRT).

RESULTS

One-hundred-fourteen subjects (58% female, median age at last visit 15.2 years) were included. Eighty-eight (77%) underwent pacemaker implantation, with median age at placement 1.9 years (IQR, 0.1-8.0 years). Twenty-six subjects (23%) reached the primary outcome - 7 (6%) died and 14 (12%) were diagnosed with heart failure and/or cardiomyopathy. Median time from diagnosis to primary outcome was 3.1 years (IQR, 0.0-10.8 years). There were no significant associations between age at diagnosis less than 1-year (hazard ratio [HR]: 1.5, 95% CI 0.6-3.9), fetal diagnosis (HR: 2.3, 0.96-5.6), or maternal antibody positivity (HR: 2.4, 0.9-6.6) and the primary outcome. Fetal diagnosis had a higher associated hazard of heart failure and/or cardiomyopathy (HR: 4.5, 1.3-15.0).

CONCLUSION

In 114 subjects with CCHB, 23% reached the composite outcome of cardiac morbidity and mortality, with no significant association between age at diagnosis, fetal diagnosis, and maternal antibody status with composite cardiac morbidity and mortality.

Safety and feasibility of conduction system pacing in patients with congenital heart disease

INTRODUCTION

Conduction system pacing (CSP) has emerged as an ideal physiologic pacing strategy for patients with permanent pacing indications. We sought to evaluate the safety and feasibility of CSP in a consecutive series of unselected patients with congenital heart disease (CHD).

METHODS

Consecutive patients with CHD in which CSP was attempted were included. Safety and feasibility, implant tools and electrical parameters at implant and at follow-up were evaluated.

RESULTS

A total of 20 patients were included (10 with a previous device). A total of 10 patients had complex forms of CHD, 9 moderate defects and 1 a simple defect. CSP was achieved in 75% of cases (10 His bundle pacing, 5 left bundle branch pacing) with left ventricular septal pacing in the remaining 5 patients. Procedure times and fluoroscopy times were prolongued (126 ± 82 min and 27 ± 30 min, respectively). Ventricular lead implant times widely varied ranging from 4 to 115 min, (mean 31 ± 28 min) and the use of multiple delivery sheaths was frequent (50%). The QRS width was reduced from 145 ± 36 ms at baseline to 116 ± 18 ms with CSP. Implant electrical parameters included: CSP pacing threshold 0.95 ± 0.65 V; R wave amplitude 9.2 ± 8.8 mV and pacing impedance 632 ± 183 Ohms, and remained stable at a median follow-up of 478 days (interquartile range: 225-567). Systemic ventricle systolic function and NYHA class (1.50 ± 0.51 vs. 1.10 ± 0.31; p = .008) significantly improved at follow-up. Lead revision was required in one patient at Day 4.

CONCLUSIONS

Permanent CSP is safe and feasible in patients with CHD although implant technique is complex.

Three-dimensional mapping for His-bundle pacing in pediatric patients, a case series

INTRODUCTION

Pediatric patients who receive pacemakers may have a lifetime of repeat exposure to fluoroscopy. His bundle pacing may provide better long-term pacing for these patients. To minimize fluoroscopy and for improved localization of the His bundle, we utilized three-dimensional mapping to guide His bundle pacing and we follow-up short-term results.

METHODS

An Octapolar Livewire catheter (Abbott, Minneapolis, USA) was used for mapping and location of the His bundle while 3-dimensional mapping via the EnSite Precision system (Abbott Medical, Abbott Park, IL) was utilized to create a 3-dimensional geometry. The EnSite Precision system also mapped and recorded His bundle signal strengths and earliest ventricular activation or retrograde His bundle activation.

RESULTS

Three patients are presented and followed for 4-5 months. The ages ranged from 10 to 15 years with 1 male patient. Diagnoses including progressive atrioventricular block, alternating bundle branch block and atrioventricular canal defect with complete heart block. All patients received selective His-bundle pacing systems. The range in fluoroscopy time was 6.4 to 9.9 min with 5.64 mGy to 10.18 mGy. Stable lead thresholds, impedances and sensing were present at last follow-up.

CONCLUSIONS

His bundle pacing in our 3 pediatric patients including one with altered His-bundle physiology (case 3 with atrioventricular canal defect) was successful with good short-term follow-up results.