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Sinus node dysfunction (SND) refers to physiologically inappropriate atrial rates, either due to sustained bradycardia or abrupt pauses in the intrinsic cardiac rhythm. In patients with isolated sinus bradycardia without symptoms due to cerebral or systemic hypoperfusion, there is no minimum heart rate or maximum pause duration where permanent pacing is recommended. ^{Reference Kusumoto, Schoenfeld and Barrett2} Establishing a temporal correlation between symptoms and age-related bradycardia is of paramount importance when determining whether permanent pacing is needed. In symptomatic patients with SND, atrial-based pacing is generally recommended over single chamber ventricular pacing. ^{Reference Gillette, Wampler and Shannon11}

Recommendation-specific supportive text

The average ventricular rate in neonates and infants with isolated CCAVB provides one objective parameter regarding the decision for pacemaker implantation. However, additional factors including birth weight (size), ventricular dysfunction, and other co-morbidities may equally influence the decision. Therefore, an average heart rate of ≤50 bpm is recommended for infant pacemaker implantation when overt symptoms related to low cardiac output are not present. Beyond the first year of life, permanent pacemaker implantation is generally indicated in symptomatic patients. Natural history studies have demonstrated progressive LV dysfunction and mitral insufficiency with cardiovascular mortality in the 4th or 5th decade in CCAVB patients who did not undergo pacemaker implantation. ^{Reference Michaëlsson and Engle17}

Recommendation-specific supportive text

Advanced AV block diagnosed during childhood or adolescence may be congenital, related to infiltrative diseases or remain idiopathic. At times, late-onset AV block may be paroxysmal and difficult to document. Exercise testing may be useful regarding the significance of AV block. When progressive AV block occurs during exercise, conduction disturbance within the His-Purkinje system is suspected and is associated with a poor prognosis. ^{Reference Yandrapalli, Harikrishnan, Ojo, Vuddanda and Jain19} With the exception of infiltrative or inflammatory causes, the criteria for pacemaker implantation are similar to those for CCAVB.

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Postoperative AV block complicates 3–8% of congenital heart surgeries, with 1–3% of patients requiring permanent pacemaker implantation for persistent postoperative AV block. ^{Reference Romer, Tabbutt and Etheridge21} A very poor prognosis has been established for CHD patients with permanent postoperative AV block who do not receive permanent pacemakers. Among patients who regain AV conduction following transient AV block, ≥85% have recovery of AV conduction by post-operative day 7 and ≥95% AV conduction by postoperative day 10. ^{Reference Weindling, Saul and Gamble20,Reference Romer, Tabbutt and Etheridge21} Although patients who regain AV conduction have a favorable prognosis, there is a small risk of late-onset complete AV block in transient postoperative AV block patients. ^{Reference Villain, Ouarda and Beyler22} Permanent pacemaker implantation may be considered for transient postoperative third-degree AV block that reverts to normal AV node conduction in patients with forms of CHD which may develop progressive AV block such as discordant AV connections, AV septal defects and heterotaxy syndromes.

Recommendation-specific supportive text

Patients with CHD often have important structural and functional lesions which influence both the indications for pacing as well as the type of pacing lead(s) utilized. Therefore, pacemaker implantation in these patients is not an isolated procedure. Bradycardia and scar related tachycardias are common following surgery, and in the absence of high-grade AV block, atrial pacing is preferred to avoid pacing-induced ventricular dysfunction. Permanent pacemaker and/or lead implantation may be considered at the time of surgery in patients with restricted vascular access or evidence of conduction disease in heart defects with a known natural progression to advanced heart block. Decisions regarding pacemaker implantation must also consider the complexity of the patient’s anatomy, surgical repair and hemodynamic status.

Recommendation-specific supportive text

Transient sinus bradycardia is common immediately after transplantation and typically resolves. In rare cases, symptomatic sinus bradycardia may persist, with at least one week allowed for recovery of sinus node function. Analysis of the United Network Organ Sharing database reported that 1% of heart transplant patients <18 years of age required a pacemaker in the acute post-transplant interval. Factors associated with need for pacing were bi-atrial anastomosis, older donor age and antiarrhythmic use. ^{Reference El-Assaad, Al-Kindi and Oliveira28} Late onset conduction disorders (sinus node or AV node dysfunction) may be related to cardiac allograft vasculopathy or allograft rejection. Patients should be evaluated for the presence of transplant coronary artery disease, as late onset bradycardia may be the first manifestation. The role of prophylactic ICD implantation is not well established but may be considered in patients who require pacemakers.

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Progressive cardiac conduction diseases are genetic disorders with deterioration of the conduction system either in isolation or in conjunction with other diseases such as neuromuscular and mitochondrial diseases. ^{Reference Feingold, Mahle and Auerbach30} Variable degrees of conduction abnormalities may occur, from first-degree AV block to complete AV block with an unpredictable progression. Laminopathies caused by mutations in the LMNA genes is a wide spectrum disorder with cardiac conduction abnormalities often observed before the onset of heart failure symptoms. ^{Reference Wahbi, Meune and Porcher32} Among the mitochondrial diseases, Kearns-Sayre syndrome, with progressive ophthalmoplegia and myopathy, has a high risk for AV block and sudden cardiac death (SCD). ^{Reference Di Mambro, Tamborrino and Silvetti31} Currently, an HRS expert consensus statement on the evaluation and management of arrhythmic risk in neuromuscular disorders is under development. Therefore, the above recommendations may be subject to modification as newer data become available.

Recommendation-Specific Supportive text

In the vast majority of cases, neurocardiogenic syncope is a limited disease and pacemaker implantation is not required. However, in some patients, recurrent syncopal events may significantly impair quality of life and may result in traumatic injury, particularly when the dominant feature of reflex syncope is cardioinhibitory. Therefore, in a highly select group of patients who fail more conservative treatment options, pacemaker therapy may be useful by preventing profound bradycardia or prolonged asystole. ^{Reference Shen, Sheldon and Benditt36} Because the efficacy of pacing depends on the clinical setting, a clear relationship between symptoms and bradycardia or asystole should be established prior to pacemaker implantation. ^{Reference Shen, Sheldon and Benditt36,Reference Brignole, Menozzi and Moya37}

Recommendation-specific supportive text

The utility of pacing as adjunctive therapy in the various channelopathies is not well defined. In patients with bradycardia-related or pause-related initiation of ventricular tachyarrhythmias, permanent pacemaker implantation may provide benefit. Also, pacing has been reported to improve outcomes in infants with prolonged QT-related functional 2:1 AV block. ^{Reference Aziz, Tanel and Zelster40} Limited data also suggest that atrial pacing faster than the intrinsic rate may shorten the QT interval and reduce the rate of recurrent syncopal events in select high-risk long QT syndrome (LQTS) patients. ^{Reference Kowlgi, Giudicessi and Brake41}

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Systemic infections may cause myocardial inflammation or infiltration presenting with bradycardia or complete AV block. In most cases, there is recovery of AV conduction. However, in chronic Chagas disease, advanced heart block in Chagas is permanent and pacemaker implantation is indicated. ^{Reference Nunes, Beaton and Acquatella43} Limited data suggest that children who develop AV block due to coronavirus 2019 (COVID-19)–related multisystem inflammatory syndrome will have recovery of normal AV conduction. ^{Reference Dionne, Mah and Son44}

Recommendation-specific supportive text

The decisions regarding ICD implantation pediatric patients are made in the context of both the unique aspects of device implantation as well as pathogenesis of the disease, which may evolve over time. Therefore, a pediatric cardiologist should be involved in the ICD implant decision and the procedure should be performed by a cardiologist or surgeon with special training/experience in CIED implantation in the pediatric age group. ICD implantation should be a shared decision between the patient, family, and physician. This includes the physical and psychological impact of an ICD on the patient’s well-being. Furthermore, the indications for the ICD should be reconsidered at each reintervention with respect to current guidelines, especially after a period of nonuse, as discontinuation of device therapy may be considered in select cases. ^{Reference Kini, Soufi and Deo54}

Long QT syndrome

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Both phenotypic and genotypic characteristics are used to guide risk stratification when patients with LQTS may require ICD therapy. ^{Reference Liu, Jons and Moss61} Phenotypic risk factors include the onset of symptoms at age <10 years, patients with prior SCA or those with recurrent syncope. Additional high-risk factors include a QTc ≥ 550 ms regardless of genotype, QTc ≥ 500 ms with LQT1, females with LQT2 and males with LQT3 genotype. Non-selective beta blockers are considered first line therapy and can significantly decrease subsequent cardiac events in patients, especially in those with KCNQ1 mutations. ^{Reference Al-Khatib, Stevenson and Ackerman45} In addition, beta-blockers and cardiac sympathetic denervation without ICD may be appropriate in carefully selected patients. ^{Reference Moss, Zareba and Hall58} Conversely, ICD implantation in an asymptomatic low-risk patient with LQTS for a positive family history of LQTS related SCD is not clearly supported by published data and requires case-specific decision making.

Catecholaminergic polymorphic ventricular tachycardia

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SCA/SCD is reported in 3 to 13% of CPVT patients. ^{Reference van der Werf, Lieve and Bos49,Reference Roston, Jones and Hawkins62} High-risk factors include male gender, previous history of cardiac arrest, multiple genetic variants, and younger age at diagnosis. Complex ventricular ectopy on exercise testing despite optimal medical therapy is also associated with worse outcome. Treatment with nonselective beta blockers is associated with a significant reduction in adverse cardiac events, while the addition of flecainide to refractory patients may provide further benefit. In general, ICD implantation should be reserved for CPVT patients with prior SCA or with refractory ventricular arrhythmias on combination medical therapy. ^{Reference van der Werf, Lieve and Bos49,Reference Roston, Jones and Hawkins62} Inappropriate shocks are reported in 20–30% of CPVT patients with ICDs with cardiac sympathetic denervation recommended in patients who experience recurrent ICD shocks. ^{Reference Roston, Jones and Hawkins62} In selected patients with aborted SCA as the initial presentation of CPVT, pharmacologic therapy and/or cardiac sympathetic denervation without ICD may be considered as a possible alternative.

Brugada syndrome

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Although Brugada syndrome presents typically in the 4th to 5th decade, it may have onset during childhood, with rapid progression leading to life-threatening arrhythmias. The ICD remains the only therapy with proven efficacy for the management of ventricular arrhythmias or SCA in patients with Brugada syndrome. ^{Reference Gonzalez Corcia and Sieira65} Adult recommendations for risk stratification including ventricular stimulation have been established, but have not been validated in pediatrics. Findings associated with high risk of ventricular arrhythmias and SCD in children include in order of relevance: the presence of symptoms (SCD or arrhythmogenic syncope), spontaneous coved type ST elevation (type I electrocardiogram [ECG] pattern), atrial arrhythmias and/or sinus node dysfunction and conduction abnormalities (AV block or intra-ventricular conduction delay). ^{Reference Gonzalez Corcia, Sieira and Pappaert67} Conversely, implantation of an ICD is not indicated in asymptomatic patients in the absence of risk factors. Further studies are necessary to further characterize risk factors and primary prevention ICD indications for pediatric patients with Brugada syndrome.

Hypertrophic cardiomyopathy

Recommendation-specific supportive text

Estimates for SCD rates in childhood hypertrophic cardiomyopathy (HCM) vary widely, with epidemiologic studies reporting rates between 1 and 7% per year. While ICDs have improved the outcomes for HCM patients resuscitated from SCD, accurate identification of risk factors to guide primary prevention ICD implantation remains a challenge, particularly given the potential progression of the disease process over time. ^{Reference Balaji, DiLorenzo and Fish71} Adult clinical practice guidelines define high risk for SCD in HCM by the presence of ≥1 defined clinical risk factors. ^{Reference Al-Khatib, Stevenson and Ackerman45,Reference Ommen, Mital and Burke69} However, recent pediatric studies suggest that the significance of adult risk factors may differ in children. A multi-center pediatric study reported that an LV posterior wall thickness z score ≥5 was associated with SCA, while a meta-analysis of pediatric studies reported a maximum LV wall thickness ≥30 mm or a z-score ≥6 associated with an increased risk of SCD. ^{Reference Balaji, DiLorenzo and Fish71} The significance of secondary risk factors for SCD, such as late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (MRI) and the role of genetic testing for specific “malignant” sarcomere mutations, remains debated and requires further investigation before inclusion as specific risk factors for SCD in pediatric patients with HCM.

Arrhythmogenic cardiomyopathies

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Arrhythmogenic cardiomyopathy (ACM) encompasses a spectrum of primary myocardial disorders with the key feature of presentation with sustained arrhythmias. ^{Reference Towbin, McKenna and Abrams72} This includes genetic disorders such as arrhythmogenic right/left ventricular cardiomyopathy, lamin A/C mutations, filamin-C, phospholamban, and cardiac amyloidosis. These entities are infrequent before puberty, and often overlap with other cardiomyopathies. Overall, SCD occurs in 2–15% of young patients with ACM. Patients presenting with SCD and/or sustained VT have a class I ICD indication. Although risk stratification data are minimal, ICD implantation is reasonable in ACM patients with hemodynamically tolerated sustained VT, syncope presumed due to ventricular arrhythmia, or an LVEF ≤ 35%. Heart transplantation and whether a wearable external defibrillator is reasonable should be considered on an individual basis for those patients with advanced heart failure.

Nonischemic dilated cardiomyopathy

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The annual incidence of SCD in pediatric patients with NIDCM is 1–5%, which is significantly less than in adult NIDCM patients. ^{Reference Pahl, Sleeper and Canter75} Although studies have shown ICD survival benefit for secondary prevention in pediatric NIDCM, the low incidence of events has made it difficult to establish risk factors to guide recommendations for primary prevention ICD implantation. ^{Reference Dubin, Berul and Bevilacqua73} However, in contrast to studies of adult patients with NIDCM and LVEF ≤ 35%, there is no clear evidence that ICDs implanted for primary prevention improve survival for pediatric patients with NIDCM. The phenotype of NIDCM may overlap with other cardiomyopathies resulting in variable risks of SCD. In the Sudden Death in Childhood Cardiomyopathy study, the cumulative incidence of SCD at 15 years was 5% for NIDCM compared to 23% for left ventricular noncompaction (LVNC). ^{Reference Bharucha, Lee and Daubeney74} Myocardial dysfunction and/or a history of clinically significant arrhythmias were strongly associated with mortality in LVNC. Therefore, factors which influence implantation of a primary prevention ICD include the NIDCM etiology, the cardiomyopathy phenotype, the degree of ventricular dysfunction and the presence of cardiac arrhythmias.

Recommendation-specific supportive text

The association between CHD and ventricular arrhythmias is well established. First demonstrated in repaired tetralogy of Fallot, studies have identified risk factors for VT and SCD including residual cardiac defects, abnormal hemodynamics, and scar from prior interventions/surgeries. While correction of residual abnormalities or ablation of arrhythmogenic substrate may improve ventricular function or reduce symptoms, these may be inadequate to prevent subsequent VT or SCA. ICD placement may therefore be appropriate in patients with, or at high risk of, potentially life-threatening arrhythmias. The role of programmed stimulation and presence and degree of ventricular dysfunction as risk factors for SCD in CHD continues to be debated. ICD implantation in patients with CHD must consider anatomy, intracardiac shunts and vascular access. This may require non-standard approaches such as epicardial leads or subcutaneous ICDs.

Recommendation specific supportive text

The use of shared decision-making should occur prior to all CIED implantation procedures. Clinicians must estimate and clearly describe the potential benefits and risks for the patient and their family. Some decisions will be relatively straightforward; for example, the decision to implant a permanent pacemaker to treat postoperative surgical complete heart block in a patient who is pacemaker dependent will be largely uncontestable. However, other treatment decisions, such as implantation of an ICD for primary prevention of SCD, are more complex and nuanced and include choice of ICD system, device location, and personalized estimation of risk of life-threatening arrhythmia for the particular patient over time.