Utilizing median and maximum QTc values improves prediction of breakthrough cardiac events in pediatric long QT syndrome.

INTRODUCTION: Although prior studies indicate that a QTc > 500 ms on a single baseline 12-lead electrocardiogram (ECG) is associated with significantly increased risk of arrhythmic events in long QT syndrome (LQTS), less is known about the risk of persistent QT prolongation. We sought to determine QTc persistence and its prognostic effect on breakthrough cardiac events (BCEs) among pediatric patients treated for LQTS. METHODS: We performed a retrospective analysis of 433 patients with LQTS evaluated, risk-stratified, and undergoing active guideline-based LQTS treatment between 1999 and 2019. BCEs were defined as arrhythmogenic syncope/seizure, sudden cardiac arrest (SCA), appropriate VF-terminating ICD shock, and sudden cardiac death (SCD). RESULTS: During the median follow-up of 5.5 years (interquartile range [IQR] = 3-9), 32 (7%) patients experienced a total of 129 BCEs. A maximum QTc threshold of 520 ms and median QTc threshold of 490 ms were determined to be strong predictors for BCEs. A landmark analysis controlling for age, sex, genotype, and symptomatic status demonstrated models utilizing both the median QTc and maximum QTc demonstrated the highest discriminatory value (c-statistic = 0.93-0.95). Patients in the high-risk group (median QTc > 490 ms and maximum QTc > 520 ms) had a significantly lower BCE free survival (70%-81%) when compared to patients in both medium-risk (93%-97%) and low-risk (98%-99%) groups. CONCLUSIONS: The risk of BCE among patients treated for LQTS increases not only based upon their maximum QTc, but also their median QTc (persistence of QTc prolongation). Patients with a maximum QTc > 520 ms and median QTc > 490 ms over serial 12-lead ECGs are at the highest risk of BCE while on guideline-directed medical therapy.

Utility of routine follow-up defibrillation safety margin testing in young patients with epicardial implantable cardioverter-defibrillators.

BACKGROUND: Routine defibrillation threshold testing (DFT) of transvenous implantable defibrillators (ICDs) has largely been in decline. In patients with non-transvenous ICDs that utilize subcutaneous and pleural ICD leads, serial DFT testing can detect a significant number of failures. Data about the utility of follow-up defibrillation safety margin testing (DSM) testing in pediatric patients and young adults with an epicardial ICD are lacking. METHODS: Patients aged < 25 years old who underwent epicardial ICD placement at Mayo Clinic from 2014 to 2023 with at least one follow-up DSM test were included. The patients were divided into a "routine" (R) and "clinically indicated" (CI) group based on the index of clinical concern. Inadequate DSM was defined as unsuccessful defibrillation at an output of less than 10 J below the maximum output of the device. The purpose of this study was to assess the utility of follow-up DSM testing. RESULTS: An epicardial ICD system was placed in 122 patients. A total of 26 patients met inclusion criteria and underwent a total of 47 DSM follow up tests. Inadequate DSM occurred in 1/33 (3%) in the R group and 2/14 (14%) DSM tests in the CI group. The median follow-up period was 54 and 36 months for the R and CI group, respectively. CONCLUSIONS: Our data suggest that epicardial ICDs are reliable and routine follow-up DSM testing may not be necessary for all patients. DSM testing should be performed in individuals with epicardial ICD systems when there is clinical concern about lead or coil performance.

Empiric Slow Pathway Cryoablation in Symptomatic Children Without Documented Supraventricular Tachycardia.

In symptomatic children without documented supraventricular tachycardia (SVT) and non-inducible atrioventricular nodal reentry tachycardia (AVNRT) the benefit of empiric slow pathway (SP) ablation is unknown. We evaluated 62 symptomatic patients without documented SVT that underwent electrophysiology study (EPS). The purpose of this study was to determine if symptoms improved after empiric SP ablation in children without documented SVT and without inducible AVNRT. Sixty-two symptomatic patients without previously documented SVT underwent EPS; 31 (50%) had inducible AVNRT and underwent SP ablation, 20 (32%) were non-inducible and underwent empiric SP ablation, 11 (18%) were non-inducible and had no ablation. After a mean follow-up of 23 ± 18 months there was no significant difference in freedom from symptoms within the non-inducible cohort regardless of whether empiric SP ablation was performed (p = 0.135). There was a significant improvement in symptoms at follow-up after SP ablation when comparing inducible and non-inducible patients (p = 0.020). During follow-up no patients had documented SVT. Symptomatic children without documented SVT do not benefit from empiric SP ablation when AVNRT cannot be induced.

Current Interventional and Surgical Management of Congenital Heart Disease: Specific Focus on Valvular Disease and Cardiac Arrhythmias.

Successful outcome in the care of patients with congenital heart disease depends on a comprehensive multidisciplinary team. Surgery is offered for almost every heart defect, despite complexity. Early mortality for cardiac surgery in the neonatal period is ≈10% and beyond infancy is <5%, with 90% to 95% of patients surviving with a good quality of life into the adult years. Advances in imaging have facilitated accurate diagnosis and planning of interventions and surgical procedures. Similarly, advances in the perioperative medical management of patients, particularly with intensive care, has also contributed to improving outcomes. Arrhythmias and heart failure are the most common late complications for the majority of defects, and reoperation for valvar problems is common. Lifelong surveillance for monitoring of recurrent or residual structural heart defects, as well as periodic assessment of cardiac function and arrhythmia monitoring, is essential for all patients. The field of congenital heart surgery is poised to incorporate new innovations such as bioengineered cells and scaffolds that will iteratively move toward bioengineered patches, conduits, valves, and even whole organs.

Cosmetic outcomes and quality of life in children with cardiac implantable electronic devices.

BACKGROUND: Axillary implant location is an alternative implant location in patients for cardiac implantable electronic devices (CIEDs) for the purposes of improved cosmetic outcome. The impact from the patient's perspective is unknown. The purpose of this study was to compare scar perception scores and quality of life (QOL) in pediatric patients with axillary CIED implant location versus the standard infraclavicular approach. METHODS: This is a multicenter prospective study conducted at eight pediatric centers and it includes patients aged from 8 to 18 years with a CIED. Patients with prior sternotomy were excluded. Scar perception and QOL outcomes were compared between the infraclavicular and axillary implant locations. RESULTS: A total of 141 patients (83 implantable cardioverter defibrillator [ICD]/58 pacemakers) were included, 55 with an axillary device and 86 with an infraclavicular device. Patients with an ICD in the axillary position had better perception of scar appearance and consciousness. Patients in the axillary group reported, on average, a total Pediatric QOL Inventory score that was 6 (1, 11) units higher than the infraclavicular group, after adjusting for sex and race (P = 0.02). CONCLUSIONS: QOL is significantly improved in axillary in comparison to the infraclavicular CIED position, regardless of device type. Scar perception is improved in patients with ICD in the axillary position.

Outcomes of atrial arrhythmia radiofrequency catheter ablation in patients with Ebstein's anomaly.

Aims: Atrial arrhythmias are common in patients with Ebstein's anomaly (EA) despite cardiac surgical repair and concomitant Maze procedures. We aimed to evaluate the outcome of radiofrequency catheter ablation in this group of patients. Methods and results: All patients with EA and atrial arrhythmias who underwent catheter ablation for atrial arrhythmias between 1/1999 and 1/2016 were included. Atrial arrhythmia recurrence was identified as the primary outcome; secondary outcomes included repeat ablation, need for antiarrhythmic medications after ablation, and death. Predictors of recurrence were sought using univariate analysis. 22 patients (median age 42 years, 54.5% male) were included. Atrial flutter was the most common presenting arrhythmia (n = 14 patients, 63.5%), whereas focal atrial tachycardia (FAT) and atrial fibrillation were identified in 5 (22.7%) and 2 patients (9.1%), respectively, with both atrial flutter/fibrillation evident in a single patient 1 (4.5%). 8 patients (36.4%) had a history of right-sided maze procedures. Cavotricuspid isthmus atrial flutter (CTI-AFl) was the most commonly induced arrhythmia (n = 13, 59.1%), followed by incisional intra-atrial re-entrant tachycardia (IART; n = 4, 18.2%), and FAT (n = 4, 18.2%); 3 patients also underwent left-side ablation with concomitant pulmonary vein isolation (13.6%). 1-year and 5-year atrial arrhythmia recurrence rates were 10.0% and 41.2%, respectively. 7 patients (31.8%) underwent redo ablations, and anti-arrhythmic medication was utilized in 8 patients (36.4%) post-ablation. Neither ablation location nor echocardiographic parameters were found to be predictors of arrhythmia recurrence. Conclusion: Catheter ablation of atrial arrhythmias in patients with EA has a favorable outcome overall with an acceptable recurrence and safety profile; left-sided ablations are rarely necessary. Despite prior Maze and catheter ablation procedures, CTI-AFl and IART recurrences predominate.

Intravascular and hybrid intraoperative stent placement for baffle obstruction in transposition of the great arteries after atrial switch.

OBJECTIVES: To report our experience with intravascular and hybrid intra-operative stent placement for baffle obstruction in patients with complete transposition of the great arteries (TGA) after the atrial switch (Mustard/Senning) operation. BACKGROUND: Venous baffle obstruction is a challenging complication after atrial switch operation in patients with TGA. Traditional treatment options include intravascular stenting or surgery. METHODS: A retrospective analysis of Mayo Clinic's electronic medical record was completed to identify consecutive pediatric and adult patients with TGA after atrial switch who underwent baffle stent implantation from 1994 to 2015. RESULTS: Overall, 64 patients were referred for cardiac catheterization, in whom 47 (73%) were noted to have hemodynamic and angiographic evidence of baffle obstruction. A total of 20 patients mean age 33 (range: 8-46) years old underwent stent implantation of baffle stenosis at a mean of 33 (range: 7.5-45) years after initial atrial switch operation (Mustard, n = 19; Senning, n = 1). Overall, 27 baffles were stented in 20 patients via the following approaches: intravascular (17); hybrid surgical (3); staged intravascular & hybrid (2). Sites of stent placement were: superior vena cava (SVC) (13); inferior vena cava (IVC) (9); pulmonary venous baffle (5). Three patients had stent placement in the SVC and IVC baffles during the same procedure. Procedural adverse events occurred in 2/22 cases (9%) including creation of unintentional baffle leak (n = 1) and stent migration (n = 1). There was no procedure-related mortality. At follow-up (median 2, range 0.02-10 years), significantly improved NYHA class and mean Doppler baffle gradient were demonstrated (P < 0.05). Mild baffle re-stenosis (mean Doppler gradient; 2-3 mmHg) occurred in two patients who have not required re-intervention. Trivial baffle leak was noted in four patients. Baffle re-intervention was only occurred in one patient. One patient with pre-procedural Class IV symptoms died 3.5 months after stent implantation. CONCLUSIONS: This study is the largest reported experience of intravascular and intra-operative hybrid stent placement for patients with TGA after atrial switch. Transcatheter and minimally invasive hybrid intraoperative surgical stent placement are an effective strategy for relief of systemic and pulmonary venous baffle obstruction. © 2016 Wiley Periodicals, Inc.

Lead extraction outcomes in patients with congenital heart disease.

AIMS: Patients with congenital heart disease (CHD) are at increased risk for intracardiac device malfunction and infection that may necessitate extraction; however, the risk of extraction is poorly understood. This study addresses the safety of extraction in patients with structural heart disease and previous cardiac surgery. METHODS AND RESULTS: This retrospective study included 40 CHD and 80 matched control patients, who underwent transvenous lead extractions between 2001 and 2014. Only leads >12 months were included. There were 77 leads in CHD patients and 146 in controls. The mean age was 38 ± 16 years in CHD patients. Ninety per cent of CHD patients had ≥1 cardiac surgeries when compared with 21% of controls (P < 0.001). The number of abandoned leads was significantly different (17 vs. 3, P < 0.001). Lead age was similar with an average duration of 83 ± 87 months in CHD patients and 62 ± 65 months in controls (P = 0.24). There was no significant difference in extraction techniques. Manual traction was successful in 40% of CHD patients and 47% of controls, and advanced techniques were used in 60 and 53% of CHD patients and controls, respectively. Complete extraction was achieved in 94% of the patients in both groups. There was no significant difference in complications. CONCLUSION: Lead extraction can be safely performed in patients with CHD. Despite anatomic abnormalities and longer implantation times, the difficulty of lead extraction in patients with CHD is comparable with controls.

Electrocardiographic abnormalities in elite high school athletes: comparison to adolescent hypertrophic cardiomyopathy.

BACKGROUND: In athletes, ECG changes from physiological cardiac remodelling are common but can overlap with findings from a pathological disorder. We compared ECG findings in a group of elite high school athletes to a cohort of adolescents with hypertrophic cardiomyopathy (HCM). METHODS/RESULTS: We prospectively performed 15-lead ECGs and echocardiograms in 147 elite high school athletes. Student-athlete ECGs were compared in blinded fashion to ECGs of 148 adolescents with HCM of similar age and ethnicity. Standard ECG hypertrophy criteria and established expert opinion guidelines (European Society of Cardiology, ESC and Seattle criteria) were analysed. All student-athletes had normal echocardiograms. Overall, 77/147 (52%) of student-athletes met standard ECG criteria for ventricular hypertrophy compared to 126/148 (85%) adolescents with HCM (p<0.0001). There were 112/148 (76%) adolescents with HCM who had pathological Q-waves, T-wave inversion and/or ST-segment depression compared to 1/147 (1%) athletes (p<0.0001). Most patients with HCM (84%, 124/148) had ≥1 abnormal ECG finding(s) according to Seattle criteria, compared to 1% of student-athletes (2/147). Similarly, 130/148 (88%) patients with HCM met group-2 ESC criteria (abnormal), compared to 36/147 (24%) student-athletes (p<0.0001). CONCLUSIONS: Over 50% of elite high school athletes with echocardiographically confirmed normal hearts satisfied standard voltage criteria for ventricular hypertrophy. Pathological Q-waves, T-wave inversion or ST-segment depression were most helpful in distinguishing adolescents with HCM from normals. Both ESC and Seattle criteria successfully stratified the student-athlete and HCM cohorts, however each had a false-negative rate >10% for the HCM cohort. The Seattle criteria demonstrated a significantly lower false-positive rate (1%) than the ESC criteria (24%).

Radiofrequency Ablation in the Sinus of Valsalva for Ventricular Arrhythmia in Pediatric Patients.

The need to perform catheter ablation of ventricular arrhythmia from within the sinuses of Valsalva in a pediatric patient is uncommon. This has been reported in adults, but there are little data about the feasibility, safety or efficacy of catheter ablation in the sinuses of Valsalva in the pediatric patients. This is a retrospective review of all patients aged 18 years or less, at two separate institutions with no structural heart disease that underwent an ablation procedure for ventricular arrhythmia mapped to the sinus of Valsalva from 2010 to 2015. We identified 8 total patients meeting inclusion criteria. Median age was 16 years and the median weight was 61 kg. All patients were symptomatic or had developed arrhythmia-induced ventricular dysfunction. Ablation was performed in the left sinus in 4 patients and the right sinus in 4 patients. No ablations were required in the non-coronary sinus. All 8 patients had an acutely successful ablation using radiofrequency energy. There were no complications. At a mean follow-up of 7 months (4-15 months), all patients were known to be living. Follow-up data regarding arrhythmia were available in 6 of the 8 patients, and none had recurrence of their ventricular arrhythmia off of all antiarrhythmic medications. Radiofrequency catheter ablation of ventricular arrhythmia in the sinus of Valsalva can be done safely and effectively in pediatric patients.

Sudden cardiac arrest during sex in patients with either catecholaminergic polymorphic ventricular tachycardia or long-QT syndrome: a rare but shocking experience.

BACKGROUND: Patients with catecholaminergic polymorphic ventricular tachycardia (CPVT) and long-QT syndrome (LQTS) are susceptible to cardiac events during sympathetic nervous system activation. Herein, we sought to determine the risk of cardiac events associated with sex in CPVT and LQTS patients. METHODS AND RESULTS: We reviewed the electronic medical record of patients seen in the Genetic Heart Rhythm Clinic. There were 445 patients ≥ 18 years diagnosed with LQTS (N = 402, age at diagnosis 30 ± 16 years) or CPVT (N = 43, age at diagnosis 25 ± 15 years). No sex-induced cardiac events occurred in the LQTS population, and 2 occurred in the CPVT population. Sex-induced events were more likely in CPVT (2/43, 4.7%) than LQTS (0/402, 0%, P = 0.008). One case involved a 22-year-old CPVT1 female with prior cardiac arrest, who experienced several appropriate implantable cardioverter defibrillator shocks during intercourse while taking ß-blockers. The second case was a 52-year-old CPVT1 male with history of recurrent exercise-triggered syncope, who had syncope during sex in the setting of ß-blocker noncompliance. Extrapolating from published estimates of intercourse frequency by age, the overall event rate was only 0.0004%, and 0.005% among the CPVT cohort. CONCLUSIONS: Potentially life-threatening cardiac events during sex in patients with CPVT are rare and even rarer in LQTS. Overall, the cardiac event per intercourse rate is extremely low. Patients and their partners should be reassured that sex is a low-risk activity from a cardiac standpoint.

Atypical atrioventricular nodal reentry tachycardia in a child with polyvalvular dysplasia.

A 10-year-old boy with polyvalvular dysplasia and severe involvement of both atrioventricular valves presented with palpitations. Concern was raised for atrial tachyarrhythmia due to biatrial enlargement; however, ambulatory monitoring discovered a reentrant mechanism. Electrophysiology study revealed atypical atrioventricular nodal reentrant tachycardia involving two components of the slow pathway, with inputs in the posterior septum around his dysplastic tricuspid valve. He underwent successful modification of the slow pathway using cryoablation.

Multi-institutional study of implantable defibrillator lead performance in children and young adults: results of the Pediatric Lead Extractability and Survival Evaluation (PLEASE) study.

BACKGROUND: Implantable cardioverter-defibrillator (ICD) therapy in children and congenital heart disease patients is hampered by poor long-term lead survival. Lead extraction is technically difficult and carries substantial morbidity. We sought to determine the outcomes of ICD leads in pediatric and congenital heart disease patients. METHODS AND RESULTS: The Pediatric Lead Extractability and Survival Evaluation (PLEASE) is a 24-center international registry. Pediatric and congenital heart disease patients with ICD lead implantations from 2005 to 2010 were eligible. Study subjects comprised 878 ICD patients (44% congenital heart disease). Mean±SD age at implantation was 18.6±9.8 years. Of the 965 total leads, 54% were thin (≤7F), of which 57% were Fidelis, and 23% were coated with expanded polytetrafluoroethylene. There were 139 ICD lead failures (14%) in 132 patients (15%) at a mean lead age of 2.0±1.4 years, causing shocks in 53 patients (40%). Independent predictors of lead failure included younger implantation age and Fidelis leads. Actuarial analysis showed an incremental risk of lead failure with younger age at implantation: <8 years compared with >18 years (P=0.015). The actuarial yearly failure rate was 2.3% for non-Fidelis and 9.1% for Fidelis leads. Extraction was performed on 143 leads (80% thin, 7% expanded polytetrafluoroethylene coated), with lead age as the only independent predictor for advanced extraction techniques. There were 6 major extraction complications (4%) but no procedural mortality. CONCLUSIONS: This study demonstrates that ICD leads in children and congenital heart disease patients have an age-related suboptimal performance, further compounded by a high failure rate of Fidelis leads. Advanced extraction techniques were common and correlated with older lead age. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00335036.

Normal electrocardiographic findings: recognising physiological adaptations in athletes.

Electrocardiographic changes in athletes are common and usually reflect benign structural and electrical remodelling of the heart as a physiological adaptation to regular and sustained physical training (athlete's heart). The ability to identify an abnormality on the 12-lead ECG, suggestive of underlying cardiac disease associated with sudden cardiac death (SCD), is based on a sound working knowledge of the normal ECG characteristics within the athletic population. This document will assist physicians in identifying normal ECG patterns commonly found in athletes. The ECG findings presented as normal in athletes were established by an international consensus panel of experts in sports cardiology and sports medicine.

Electrocardiographic interpretation in athletes: the 'Seattle criteria'.

Sudden cardiac death (SCD) is the leading cause of death in athletes during sport. Whether obtained for screening or diagnostic purposes, an ECG increases the ability to detect underlying cardiovascular conditions that may increase the risk for SCD. In most countries, there is a shortage of physician expertise in the interpretation of an athlete's ECG. A critical need exists for physician education in modern ECG interpretation that distinguishes normal physiological adaptations in athletes from abnormal findings suggestive of pathology. On 13-14 February 2012, an international group of experts in sports cardiology and sports medicine convened in Seattle, Washington, to define contemporary standards for ECG interpretation in athletes. The objective of the meeting was to develop a comprehensive training resource to help physicians distinguish normal ECG alterations in athletes from abnormal ECG findings that require additional evaluation for conditions associated with SCD.

Abnormal electrocardiographic findings in athletes: recognising changes suggestive of cardiomyopathy.

Cardiomyopathies are a heterogeneous group of heart muscle diseases and collectively are the leading cause of sudden cardiac death (SCD) in young athletes. The 12-lead ECG is utilised as both a screening and diagnostic tool for detecting conditions associated with SCD. Fundamental to the appropriate evaluation of athletes undergoing ECG is an understanding of the ECG findings that may indicate the presence of an underlying pathological cardiac disorder. This article describes ECG findings present in cardiomyopathies afflicting young athletes and outlines appropriate steps for further evaluation of these ECG abnormalities. The ECG findings defined as abnormal in athletes were established by an international consensus panel of experts in sports cardiology and sports medicine.

Abnormal electrocardiographic findings in athletes: recognising changes suggestive of primary electrical disease.

Cardiac channelopathies are potentially lethal inherited arrhythmia syndromes and an important cause of sudden cardiac death (SCD) in young athletes. Other cardiac rhythm and conduction disturbances also may indicate the presence of an underlying cardiac disorder. The 12-lead ECG is utilised as both a screening and a diagnostic tool for detecting conditions associated with SCD. Fundamental to the appropriate evaluation of athletes undergoing ECG is an understanding of the ECG findings that may indicate the presence of a pathological cardiac disease. This article describes ECG findings present in primary electrical diseases afflicting young athletes and outlines appropriate steps for further evaluation of these ECG abnormalities. The ECG findings defined as abnormal in athletes were established by an international consensus panel of experts in sports cardiology and sports medicine.

Pediatric Epicardial Devices: Early and Midterm Outcomes.

BACKGROUND: Lead performance is suboptimal in young patients and a main cause of device system failure. Our objective was to assess early and midterm outcomes after epicardial device implantation in a contemporary pediatric cohort. METHODS: A total of 116 consecutive pediatric patients underwent 137 epicardial device implantations from 2010 to 2019. Forty pacemakers and 97 implantable cardioverter defibrillators (ICDs) were implanted. Lead failure was defined as leads repaired, replaced, or abandoned due to fracture, dislodgement, or dysfunction. Freedom from device system failure was determined using Kaplan-Meier analysis. RESULTS: Mean age at implantation was 10 ± 5 years, 46 (34%) were younger than 8 years old, 41 (30%) had prior cardiac surgery, and 38 (28%) had prior devices. Main indications were acquired heart block (17/40 [43%]), sinus node dysfunction (14/40 [35%]), and congenital heart block (7/40 [18%]) for pacemakers, and hypertrophic cardiomyopathy (46/97 [47%]), long QT syndrome (31/97 [32%]), and ventricular arrhythmia (17/97 [18%]) for ICDs. There were no early deaths. Three-year freedom from device system failure was 80% (95% CI 73%, 88%) for all patients and 88% (95% CI 79%, 99%) for patients <8 years old. Device system failure causes included lead fracture (20/34 [59%]), lead dysfunction (5/34 [15%]), lead dislodgement (5/34 [15%]), infection (3/34 [9%]), and pericarditis (1/34 [3%]). Reintervention was required in 26/34 (76%) device system failures. CONCLUSIONS: Epicardial device implantation is safe, shows acceptable midterm outcomes in children, and is an effective option in patients younger than 8 years old. Close device surveillance continues to be essential to detect lead failure early and ensure timely reintervention.

Asymptomatic Apical Hypertrophic Cardiomyopathy in an Elite Competitive Athlete.

A 17-year-old male elite athlete presented for evaluation after an abnormal pre-competitive college screening electrocardiogram. Subsequent evaluation revealed the presence of hypertrophic cardiomyopathy. He remained asymptomatic throughout four years of follow-up. Through shared decision making, he continued to play competitively and is now a professional athlete. (Level of Difficulty: Advanced.).

Septal Myectomy Outcomes in Children and Adolescents With Obstructive Hypertrophic Cardiomyopathy.

BACKGROUND: Little data exist regarding characteristics and outcomes of pediatric patients undergoing septal myectomy. We evaluated this in a large referral population. METHODS: Septal myectomy was performed in 199 consecutive patients aged ≤18 years with obstructive hypertrophic cardiomyopathy from January 1, 1976, to June 30, 2021. RESULTS: Median age was 13 years (interquartile range [IQR], 8-15 years). Left ventricular myectomy approaches included transaortic (163 of 198 [82%]), transapical (16 of 198 [8%]), and combined (19 of 198 [10%]). Right ventricular interventions included myectomy (13 of 199 [7%]) and patch reconstruction of the outflow tract (15 of 199 [8%]). Maximum left ventricular outflow tract gradients decreased after myectomy (prebypass: 50 mm Hg [IQR, 31-73 mm Hg] vs postbypass: 4 mm Hg [IQR, 0-9 mm Hg], P < .001), and this was sustained long-term (5 mm Hg [IQR, 5-10 mm Hg] at 10 years). Iatrogenic aortic and mitral valve injuries occurred in 13 of 199 (7%) and 1 of 199 (1%), respectively; however, all were successfully repaired. Operative mortality was 2 of 199 (1%). The cumulative incidence of redo myectomy was low, at 5.8% at 5 and 8.3% at 10 years. Redo myectomy patients had higher maximum left ventricular outflow tract gradients on echocardiography at predischarge and 1 year and were younger at the index operation (8 years [IQR, 2.5-10 years] vs 13 years [IQR, 9-16 years], P < .001). Overall survival at 10 years was 90%, relative to 47% in a previously reported pediatric nonoperative cohort. CONCLUSIONS: Pediatric septal myectomy provides safe, effective, and durable relief of ventricular outflow tract obstruction. Iatrogenic valve injury remains a low but nonnegligible risk. Recurrent obstruction requiring redo myectomy is infrequent and can be identified early. Long-term survival in this pediatric septal myectomy cohort appears to fare better than pediatric hypertrophic cardiomyopathy cohorts managed nonoperatively.