Assessment of paediatric exertional or peri-exertional syncope: does the story matter?

Exertional syncope has been suggested to correlate with a cardiac aetiology, particularly when occurring in mid-stride. The aim of the study is to evaluate the incidence of cardiac disease among children presenting with exertional syncope, determine the influence of timing within activity, and determine the utility of genetic testing and implantable event monitors in the evaluation of cardiac syncope. The patients ≤18 years old with exertional syncope who underwent exercise stress testing between 2008 and 2019 were retrospectively included. Patients were assessed to be in one of three groups: mid-exertion (mid-stride syncope), peri-exertion (syncope during activity but not moving), and post-exertion (within minutes of the activity). A total of 334 patients were included; 46 % were mid-exertion, 18 % were peri-exertion, and 36 % were post-exertion. Thirteen patients (3.8 %) were diagnosed with cardiac syncope; n = 9 (69 %) mid-exertion. Only mid-exertional syncope was significantly associated with a cardiac diagnosis (OR: 2.6). Cardiac diagnoses included inherited arrhythmia syndromes (n = 9), abnormal coronary origins (n = 2), and supraventricular tachycardia (n = 2). Only catecholaminergic polymorphic ventricular tachycardia (n = 5) was associated with mid-exertional syncope (OR: 1.4). The definitive diagnostic test was exercise testing (n = 8), echocardiogram (n = 2), genetic testing (n = 1), ambulatory monitor (n = 1), and EKG (n = 1). Mid-stride syncope was more likely to result in a cardiac diagnosis, and exercise testing is the most common definitive test as catecholaminergic polymorphic ventricular tachycardia was the primary aetiology of exertional syncope in our cohort. Implantable event monitors and genetic testing could be helpful in ruling out cardiac disease.

An International Multicenter Evaluation of Inheritance Patterns, Arrhythmic Risks, and Underlying Mechanisms of CASQ2-Catecholaminergic Polymorphic Ventricular Tachycardia.

BACKGROUND: Genetic variants in calsequestrin-2 (CASQ2) cause an autosomal recessive form of catecholaminergic polymorphic ventricular tachycardia (CPVT), although isolated reports have identified arrhythmic phenotypes among heterozygotes. Improved insight into the inheritance patterns, arrhythmic risks, and molecular mechanisms of CASQ2-CPVT was sought through an international multicenter collaboration. METHODS: Genotype-phenotype segregation in CASQ2-CPVT families was assessed, and the impact of genotype on arrhythmic risk was evaluated using Cox regression models. Putative dominant CASQ2 missense variants and the established recessive CASQ2-p.R33Q variant were evaluated using oligomerization assays and their locations mapped to a recent CASQ2 filament structure. RESULTS: A total of 112 individuals, including 36 CPVT probands (24 homozygotes/compound heterozygotes and 12 heterozygotes) and 76 family members possessing at least 1 presumed pathogenic CASQ2 variant, were identified. Among CASQ2 homozygotes and compound heterozygotes, clinical penetrance was 97.1% and 26 of 34 (76.5%) individuals had experienced a potentially fatal arrhythmic event with a median age of onset of 7 years (95% CI, 6-11). Fifty-one of 66 CASQ2 heterozygous family members had undergone clinical evaluation, and 17 of 51 (33.3%) met diagnostic criteria for CPVT. Relative to CASQ2 heterozygotes, CASQ2 homozygote/compound heterozygote genotype status in probands was associated with a 3.2-fold (95% CI, 1.3-8.0; P=0.013) increased hazard of a composite of cardiac syncope, aborted cardiac arrest, and sudden cardiac death, but a 38.8-fold (95% CI, 5.6-269.1; P<0.001) increased hazard in genotype-positive family members. In vitro turbidity assays revealed that p.R33Q and all 6 candidate dominant CASQ2 missense variants evaluated exhibited filamentation defects, but only p.R33Q convincingly failed to dimerize. Structural analysis revealed that 3 of these 6 putative dominant negative missense variants localized to an electronegative pocket considered critical for back-to-back binding of dimers. CONCLUSIONS: This international multicenter study of CASQ2-CPVT redefines its heritability and confirms that pathogenic heterozygous CASQ2 variants may manifest with a CPVT phenotype, indicating a need to clinically screen these individuals. A dominant mode of inheritance appears intrinsic to certain missense variants because of their location and function within the CASQ2 filament structure.

Transesophageal three-dimensional echocardiographic guidance for pacemaker lead extraction.

BACKGROUND: The ability of transesophageal three-dimensional echocardiography (3DE) to aid in pacemaker lead extraction has not yet been evaluated. 3DE provides real-time evaluation of intracardiac anatomy and the location of pacemaker leads in greater detail than either fluoroscopy or -two-dimensional echocardiography (2DE), aiding in the extraction of such leads, which can be potentially dangerous. We sought to investigate the feasibility and utility of 3DE to visualize intracardiac anatomy and pacemaker leads, and to assist in lead extraction procedures. METHODS: We utilized 3DE in nine encounters for eight different patients, to visualize intracardiac anatomy and leads before, during, and after extraction to evaluate the feasibility and utility to aid in the procedure and evaluate for potential sequelae. RESULTS: 3DE was able to identify pertinent intracardiac anatomy and leads in all cases. 3DE detected procedural complications or altered management in five of nine encounters (five of eight patients); this included detection of an avulsed papillary muscle, tricuspid valve leaflet damage, and cast/thrombus after lead removal, as well as adjustment of excess lead slack to avoid future valve damage, or risk stratification of lead removal. CONCLUSION: 3DE is feasible and adds utility to lead extraction cases by visualizing intracardiac anatomy and leads beyond fluoroscopy or 2DE, providing real-time information during extraction, and identifying potential complications.

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.

The clinical and genetic spectrum of catecholaminergic polymorphic ventricular tachycardia: findings from an international multicentre registry.

Aims: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an ion channelopathy characterized by ventricular arrhythmia during exertion or stress. Mutations in RYR2-coded Ryanodine Receptor-2 (RyR2) and CASQ2-coded Calsequestrin-2 (CASQ2) genes underlie CPVT1 and CPVT2, respectively. However, prognostic markers are scarce. We sought to better characterize the phenotypic and genotypic spectrum of CPVT, and utilize molecular modelling to help account for clinical phenotypes. Methods and results: This is a Pediatric and Congenital Electrophysiology Society multicentre, retrospective cohort study of CPVT patients diagnosed at <19 years of age and their first-degree relatives. Genetic testing was undertaken in 194 of 236 subjects (82%) during 3.5 (1.4-5.3) years of follow-up. The majority (60%) had RyR2-associated CPVT1. Variant locations were predicted based on a 3D structural model of RyR2. Specific residues appear to have key structural importance, supported by an association between cardiac arrest and mutations in the intersubunit interface of the N-terminus, and the S4-S5 linker and helices S5 and S6 of the RyR2 C-terminus. In approximately one quarter of symptomatic patients, cardiac events were precipitated by only normal wakeful activities. Conclusion: This large, multicentre study identifies contemporary challenges related to the diagnosis and prognostication of CPVT patients. Structural modelling of RyR2 can improve our understanding severe CPVT phenotypes. Wakeful rest, rather than exertion, often precipitated life-threatening cardiac events.

Atrial undersensing secondary to quiet timer blanking in pediatric and congenital heart disease patients.

BACKGROUND: Atrial undersensing despite normal atrial lead parameters and high amplitude electrograms has been described in adult patients as a consequence of atrial amplifier saturation. Repetitive inputs cause amplifier ringing and undersensing occurs as a consequence of quiet timer blanking. High amplitude ventricular electrograms can also result in atrial blanking secondary to cross-chamber effect. This has not been described in pediatric patients or epicardial pacing systems and specific risk factors are not known. We describe five cases of atrial undersensing in pediatric and congenital heart disease patients with epicardial dual-chamber systems and high ventricular lead outputs. METHODS: This was a retrospective cohort study of all patients with dual-chamber pacing systems cared for at the Heart Institute at Children's Hospital Colorado. RESULTS: Five cases of atrial undersensing with normal atrial lead parameters were found. All were epicardial systems with acceptable lead parameters at implantation and Medtronic (Medtronic, Inc., Minneapolis, MN, USA) generators with unipolar leads. Ventricular pacing outputs were elevated at presentation, median 5.5 V (5-7.5). Presenting symptoms were exercise intolerance (four) and detection on routine monitoring (one). Successful interventions included reduction in ventricular lead pacing output (one), programming of rate response (two), and implantation of an alternative generator manufacturer (two). CONCLUSION: Atrial undersensing secondary to amplifier ringing and quiet timer blanking is an uncommon presentation but may be clinically important in patients with unipolar epicardial atrial leads and high pacing outputs from ventricular leads.

Intermittent versus Persistent Wolff-Parkinson-White Syndrome in Children: Electrophysiologic Properties and Clinical Outcomes.

BACKGROUND: Intermittent Wolff-Parkinson-White (WPW) syndrome is considered to have a lower risk of sudden death. Fewer data exist regarding electrophysiologic (EP) characteristics and the natural history of intermittent WPW in children. METHODS: All patients with WPW age 1-18 years at a single institution (1996-2013) were reviewed. Patients with intermittent preexcitation were compared to those with loss of preexcitation on Holter/exercise testing and those with persistent preexcitation. High-risk accessory pathway (AP) was defined as AP effective refractory period (APERP), block cycle length, or shortest preexcited RR interval during atrial fibrillation ≤250 ms. RESULTS: A total of 295 patients were included: 226 (76.6%) persistent, 39 (13.2%) intermittent, and 30 (10.2%) loss of preexcitation Holter/exercise. There were no differences in symptoms between groups. Median interquartile range APERP was significantly longer in intermittent WPW (380 [320, 488] ms vs 320 [300, 350] ms persistent, 310 [290, 330] ms loss of preexcitation Holter/exercise; P = 0.0008). At baseline, there was no difference between groups in frequency of high-risk pathways. However, when isoproterenol values were included, high-risk pathways were more frequent among patients with loss of preexcitation on Holter/exercise (54% vs 16% persistent, 11% intermittent; P = 0.005). There was one death in a patient with loss of preexcitation on exercise testing, no EP study, and prior drug use. A second patient with persistent WPW and APERP 270 ms required resuscitation following a methadone overdose. CONCLUSION: Intermittent preexcitation in children does not connote a lower risk AP by EP criteria or reduced symptoms. The low number of pediatric WPW patients who develop preexcited atrial fibrillation or sudden death warrants larger studies to investigate these outcomes.

Pediatric & Congenital Electrophysiology Society: building an international paediatric electrophysiology organisation.

The Pediatric and Congenital Electrophysiology Society (PACES) is a non-profit organisation comprised of individuals dedicated to improving the care of children and young adults with cardiac rhythm disturbances. Although PACES is a predominantly North American-centric organisation, international members have been a part of PACES for the last two decades. This year, PACES expanded its North American framework into a broadly expansive international role. On 12 May, 2015, paediatric electrophysiology leaders from within the United States of America and Canada met with over 30 international paediatric electrophysiologists from 17 countries and five continents discussing measures to (1) expand PACES' global vision, (2) address ongoing challenges such as limited resource allocation that may be present in developing countries, (3) expand PACES' governance to include international representation, (4) promote joint international sessions at future paediatric EP meetings, and (5) facilitate a global multi-centre research consortium. This meeting marked the inception of a formal international collaborative spirit in PACES. This editorial addresses some solutions to breakdown the continental silos paediatric electrophysiologists have practiced within; however, there remain ongoing limitations, and future discussions will be needed to continue to move the PACES global international vision forward.

The fate of nontargeted endocardial leads during the extraction of one or more targeted leads in pediatrics and congenital heart disease.

INTRODUCTION: Extraction of targeted endocardial leads can lead to inadvertent damage or dislodgement of nontargeted leads, though the frequency of this has not been reported in pediatrics and congenital heart disease (CHD). METHODS: This is a retrospective review of lead extraction procedures from 2002 to 2010 from two pediatric and CHD centers evaluating unplanned interventions on nontargeted leads during the extraction of one or more targeted leads. RESULTS: Nontargeted leads were present in the 22 lead extraction procedures performed on 20 patients with median age 15 years (interquartile range, 11.5-18.5 years): 11 (55%) with structurally normal hearts and nine (45%) with CHD. Twenty of 23 targeted leads (86%) were extracted with complete success. Of the 22 nontargeted leads, including 17 atrial leads and five ventricular leads, seven (32%) required further intervention including: five extracted due to damage, dislodgement, or change in device location; one abandoned due to damage; and one dislodged requiring a second procedure for repositioning. The remaining 15 nontargeted leads (68%) were unharmed. Nontargeted leads requiring further intervention had a shorter lead duration in situ (median 2 years, interquartile range 0.5-3.5 years) than unharmed nontargeted leads (median 6.6 years, interquartile range 4.1-9.1 years; P = 0.01). Age at extraction, CHD, implantable cardioverter defibrillator leads, atrial lead position, or primary extraction modality did not predict further intervention for nontargeted leads. Major complications occurred in one procedure (4.5%) with no deaths. CONCLUSIONS: In pediatrics and CHD, nontargeted leads are frequently damaged or dislodged during the extraction of targeted leads. The risk of lead damage or dislodgement has implications for procedural planning and counseling for patients and families of pediatric and CHD patients requiring lead extraction.

Assessment of intrathoracic impedance algorithm in the pediatric and adult congenital population.

BACKGROUND: Decreased intrathoracic impedance has been used in adults to predict heart failure (HF) exacerbations. A commercial algorithm, OptiVol® (Medtronic Inc., Minneapolis, MN, USA), identifies patients with decreased impedance. We sought to determine the specificity, sensitivity, and positive predictive value (PPV) of OptiVol for predicting HF exacerbation or increased arrhythmia burden in pediatric and adult congenital heart disease (CHD) patients. METHODS: A multicenter retrospective chart review was undertaken. Inclusion criteria were: (1) <19 years or CHD adults, (2) an implanted device with OptiVol capability, (3) implanted between April 9 and September 6, and (4) follow-up of >30 days postimplant. Clinical events were defined as clinical HF exacerbation/hospital admission, initiation/uptitration of medication, or increased arrhythmia burden. RESULTS: Seventy-two patients (19 ± 9 years) were identified with the following indications: 20% dilated cardiomyopathy (DCM), 11% hypertrophic cardiomyopathy (HCM), 43% CHD, 15% channelopathy, and 11% other. Thirty-nine had 122 OptiVol crossings (median 2, range 1-11); 30% were linked to a cause. The remaining 33 had no crossing, though 17 had 89 clinical events. The clinical event rate was 19% greater in patients with crossings, though not statistically significant (P = 0.4). The algorithm had a 59% sensitivity, 52% specificity, and 62% PPV. Clinical HF exacerbation and arrhythmia burden did not significantly correlate with decreased impedance though uptitration or initiation of HF medication did correlate significantly (P = 0.03). CONCLUSION: The algorithm sensitivity for pediatric DCM, HCM, CHD, and adult CHD was equivalent to the general adult population. Further studies are warranted to assess whether inaccuracy in prediction is secondary to the algorithm or to differences in the clinical response of pediatric/CHD patients.

Preprocedural imaging in patients with transposition of the great arteries facilitates placement of cardiac resynchronization therapy leads.

OBJECTIVE: The purpose of this study is to review a series of patients with complex congenital heart disease in whom preprocedural imaging was used to assist placement of cardiac resynchronization therapy (CRT) leads. BACKGROUND: CRT may be beneficial in patients with a failing systemic ventricle and transposition of the great arteries (TGA). However, complex coronary venous anatomy can be challenging for placement of CRT leads. METHODS: Between October 2006 and June 2012, seven patients with either dextro-TGA (d-TGA) or levo-TGA (l-TGA) underwent preprocedural imaging prior to placement of CRT leads (three, d-TGA and four, l-TGA). Three patients underwent cardiac computed tomography (CT) and four underwent coronary angiography, which included levophase imaging of the coronary sinus (CS) or direct contrast injection of the CS. Where CS anatomy was appropriate with drainage into the systemic venous circulation, a transvenous approach was planned. In all other cases, the patient was referred for surgical placement of epicardial leads. RESULTS: Seven patients were identified with either d-TGA or l-TGA who had undergone preprocedural imaging prior to placement of CRT leads (three, d-TGA and four, l-TGA). Three patients underwent cardiac CT and four underwent coronary angiography, which included levophase imaging of the CS or direct contrast injection of the CS. All seven patients had successful CRT lead placement guided by preprocedure imaging. Three patients required surgical placement whereas four were able to undergo transvenous placement. There were no complications. The majority of patients (four of seven) had improvement in New York Heart Association class as well as subjective improvement in exercise tolerance and energy. The majority of patients also had subjective improvement in systemic right ventricular function by echocardiogram and objective improvement in fractional area change of the right ventricle. The follow-up period ranged from 13 months to 55 months with a mean follow-up of 39 months. CONCLUSIONS: Placement of biventricular leads for CRT in patients with l-TGA or d-TGA is feasible. Preprocedural imaging of the CS allows for better assessment of its anatomy and helps determine procedural approach for CRT placement, thereby limiting unnecessary procedures. In the majority of patients, there was subjective improvement in functional status and right ventricular function; in addition, there was objective improvement in echocardiographic parameters of right ventricular function after CRT placement.

The safety of modern anesthesia for children with long QT syndrome.

BACKGROUND: Patients with long QT syndrome (LQTS) may experience a clinical spectrum of symptoms, ranging from asymptomatic, through presyncope, syncope, and aborted cardiac arrest, to sudden cardiac death. Arrhythmias in LQTS are often precipitated by autonomic changes. This patient population is believed to be at high risk for perioperative arrhythmia, specifically torsades de pointes (TdP), although this perception is largely based on limited literature that predates current anesthetic drugs and standards of perioperative monitoring. We present the largest multicenter review to date of anesthetic management in children with LQTS. METHODS: We conducted a multicentered retrospective chart review of perioperative management of children with clinically diagnosed LQTS, aged 18 years or younger, who received general anesthesia (GA) between January 2005 and January 2010. Data from 8 institutions were collated in an anonymized database. RESULTS: One hundred three patients with LQTS underwent a total of 158 episodes of GA. The median (interquartile range) age and weight of the patients at the time of GA was 9 (3-15) years and 30.3 (15.4-54) kg, respectively. Surgery was LQTS-related in 81 (51%) GA episodes (including pacemaker, implantable cardioverter-defibrillator, and loop recorder insertions and revisions and lead extractions) and incidental in 77 (49%). ß-blocker therapy was administered to 76% of patients on the day of surgery and 47% received sedative premedication. Nineteen percent of patients received total IV anesthesia, 30% received total inhaled anesthesia, and the remaining 51% received a combination. No patient received droperidol. There were 5 perioperative episodes of TdP, all in neonates or infants, all in surgery that was LQTS-related, and none of which was overtly attributable to anesthetic regimen. Thus the incidence (95% confidence interval) of perioperative TdP in incidental versus LQTS-related surgery was 0/77 (0%; 0%-5%) vs 5/81 (6.2%; 2%-14%). CONCLUSIONS: With optimized perioperative management, modern anesthesia for incidental surgery in patients with LQTS is safer than anecdotal case report literature might suggest. Our series suggests that the risk of perioperative TdP is concentrated in neonates and infants requiring urgent interventions after failed first-line management of LQTS.

Tachyarrhythmias after the Norwood procedure: relationship and effect of vasoactive agents.

Tachyarrhythmias are common after the Norwood stage I palliation. The effects of vasoactive medications on the development of post-operative tachyarrhythmias have not been studied. The primary objective was to identify associations between postoperative tachyarrhythmias and vasoactive medication usage after Norwood stage 1 palliation. Secondary objectives included evaluation for morbidities of tachyarrhythmias and for associations with anatomical or surgical variables. Retrospective chart review was performed on all patients who underwent the Norwood stage 1 palliation at Children's Hospital Colorado between January 2008 and June 2012. Primary outcomes were development of postoperative tachyarrhythmias and the effects of vasoactive medications. Dopamine, epinephrine, milrinone, and vasopressin duration, cumulative dose, highest dose, and dose at onset of tachyarrhythmia were identified. The effects of surgical variables and anatomy were also studied. Sixty-six patients underwent the Norwood procedure, and 33 (50 %) of these patients had postoperative tachyarrhythmias. Patients with tachyarrhythmias had longer ICU stays (p = 0.02) and hospital stays (p < 0.01), but no change in mortality (p = 1.0). Multivariate Cox regression analysis showed that the right ventricle to pulmonary artery shunt (p < 0.01), longer duration of epinephrine treatment (p = 0.02), and higher milrinone dose (p = 0.002) were associated with tachyarrhythmias. Postoperative tachyarrhythmias are common after the Norwood procedure and are associated with longer ICU and hospital stays. High doses of milrinone, longer duration of epinephrine treatment, and the right ventricle to pulmonary artery shunt were associated with for the development of tachyarrhythmias. Further studies are required to determine the effects of anatomy on post-operative tachyarrhythmias.

Fascicular and nonfascicular left ventricular tachycardias in the young: an international multicenter study.

INTRODUCTION: The aim of this study was to evaluate the clinical presentation and outcomes of pediatric patients with ventricular tachycardia (VT) originating from left heart structures. METHODS AND RESULTS: This international multicenter retrospective study including 152 patients (age 10.0 ± 5.1 years, 62% male), divided into those with fascicular VT (85%, 129/152) and nonfascicular LV VT (15%, 23/152). All patients had a normal heart structure or only a minor cardiac abnormality. Adenosine was largely ineffective in both groups (tachycardia termination in 4/74 of fascicular VT and 0/5 of nonfascicular LV VT). In fascicular VT, calcium channel blockers were effective in 80% (74/92); however, when administered orally, there was a 21% (13/62) recurrence rate. In nonfascicular LV VT, a variety of antiarrhythmic therapies were used with no one predominating. Ablation procedures were successful in 71% (72/102) of fascicular VT and 67% (12/18) of nonfascicular LV VT on an intention to treat analysis. Major complications occurred in 5 patients with fascicular VT and 1 patient with nonfascicular LV VT. After a follow-up period of 2 years (1 day to 15 years), 72% of all patients with fascicular VT were off medications with no tachycardia recurrence. One patient died of noncardiac causes. In nonfascicular LV VT, follow-up was 3.5 years (0.5-15 years), P = 0.38. A total of 65% of these patients were free from arrhythmias. Two patients died suddenly (P < 0.01). CONCLUSION: The clinical course and outcomes of pediatric patients with fascicular VT and nonfascicular LV VT are varied. Catheter ablation procedures can be curative.

Percutaneous transhepatic access for catheter ablation of cardiac arrhythmias.

AIMS: Femoral venous access may be limited in certain patients undergoing electrophysiology (EP) study and ablation. The purpose of this study is to review a series of patients undergoing percutaneous transhepatic access to allow for ablation of cardiac arrhythmias. METHODS AND RESULTS: Six patients with a variety of cardiac arrhythmias and venous abnormalities underwent percutaneous transhepatic access. Under fluoroscopic and ultrasound guidance, a percutaneous needle was advanced into a hepatic vein and exchanged for a vascular sheath over a wire. Electrophysiology study and radiofrequency ablation was then performed. All tachycardias, including atrial tachycardia, atrial flutter, atrioventricular nodal tachycardia, and atrial fibrillation, were ablated. Procedural times ranged from 227 to 418 min. Fluoroscopy times ranged from 32 to 95 min. There were no complications. All six patients have been arrhythmia-free in follow-up (5-49 months, mean 23.1 months). CONCLUSION: Percutaneous transhepatic access is safe and feasible in patients with limited venous access who are undergoing EP study and ablation for a range of cardiac arrhythmias.

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.

Cryoablation for presumed atrioventricular nodal reentrant tachycardia in pediatric patients.

BACKGROUND: Little data exist on the outcomes of cryoablation for the treatment of presumptive atrioventricular nodal reentrant tachycardia (AVNRT) in a pediatric population. METHODS: We performed a retrospective chart review of patients undergoing cryoablation from January 2006 to October 2010 for presumed AVNRT at the Children's Hospital Colorado. Inclusion criteria were age ≤ 18, normal heart structure, no prior ablation procedures, documented narrow complex tachycardia, and no inducible tachycardia or other tachycardia mechanisms during electrophysiology study. RESULTS: Thirteen patients underwent cryoablation for presumed AVNRT. Cryoablation catheter tip size varied from 4 to 8 mm with a median of eight cryoablation lesions. Isoproterenol was utilized preablation in 54% and none postablation. Procedural endpoints, per written report, were loss of sustained slow pathway, change in Wenckebach cycle length, and no specific endpoint. Procedural endpoints, per measured data, were a decrease in patients exhibiting sustained slow pathway conduction. Maximum atrial-His (AH) interval with atrial overdrive pacing was reduced from 266 ms preablation to 167 ms postablation, p = 0.006. The number of patients with an AH jump was reduced from 6 to 2. After follow-up of 13.8 ± 14.3 months, 23% (3/13) had documented tachycardia recurrence. No statistical significance was determined when comparing electrophysiology testing parameters pre- and postablation among the group with recurrence versus the group without recurrence. CONCLUSIONS: Cryoablation can be considered as a safe alternative to radiofrequency ablation for the treatment of presumed AVNRT among pediatric patients, albeit with a recurrence rate of 23%.

Clinical and electrophysiologic characteristics of antidromic tachycardia in children with Wolff-Parkinson-White syndrome.

BACKGROUND: Antidromic reciprocating tachycardia (ART) is a rare form of wide complex tachycardia in children with Wolff-Parkinson-White syndrome (WPW). The incidence and electrophysiologic characteristics of ART in children with WPW have not been well described. METHODS: A multicenter retrospective analysis of all patients with WPW undergoing electrophysiology (EP) study from 1990 to 2009 was performed. Patients with clinical or inducible ART were included. RESULTS: A total of 1,147 patients with WPW underwent EP study and 30 patients had ART (2.6%) and were the subject of this analysis. The mean age was 16±3 years, weight was 65±16 kg, and tachycardia cycle length was 305±55 ms. There were two patients (7%) with congenital heart disease (both with Ebstein's anomaly). Four patients (13%) had more than one accessory pathway (AP). The location of the AP was left sided in 53% of patients and right sided in 47%, with septal location and left lateral pathways most commonly involved. AP conduction was found to be high risk in 17 patients (57%). Ablation was not attempted in two patients (7%) due to proximity to the HIS and risk of heart block. Ablation was acutely successful in 93% of the patients in whom it was attempted. CONCLUSIONS: ART is a rare finding in children undergoing EP study. Over half of the patients with ART were found to be high risk and multiple AP were uncommon. Unlike the adult population, ART occurred commonly with septal APs.

Repolarization Dispersion Is Associated With Diastolic Electromechanical Discoordination in Children With Pulmonary Arterial Hypertension.

Background Electromechanical dyssynchrony is a well described comorbidity in pulmonary arterial hypertension (PAH). ECG-derived measurements reflective of diastolic dysfunction and electromechanical imaging markers are yet to be investigated. In this study we investigated the ECG- derived marker of repolarization dispersion, interval between the peak and end of T wave (TpTe), in pediatric patients with PAH and left ventricular (LV) diastolic dysfunction. Methods and Results We measured TpTe from a standard 12-lead ECG and in 30 children with PAH and matched control subjects. All participants underwent same-day echocardiography and myocardial strain analysis to calculate the diastolic electromechanical discoordination marker diastolic relaxation fraction. When compared with control subjects, patients with PAH had increased TpTe (93±15 versus 81±12 ms, P=0.001) and elevated diastolic relaxation fraction (0.33±0.10 versus 0.27±0.03, P=0.001). Patients with PAH with LV diastolic dysfunction had significantly increased TpTe when compared with patients with PAH without diastolic dysfunction (P=0.012) and when compared with control group (P<0.001). Similarly, patients with PAH with LV diastolic dysfunction had increased diastolic relaxation fraction when compared with PAH patients without diastolic dysfunction (P=0.007) and when compared with control group (P<0.001). A 10-ms increase in TpTe was significantly associated with 0.023 increase in diastolic relaxation fraction (P=0.008) adjusting for body surface area, heart rate, right ventricular volumes, and function. Conclusions Prolonged myocardial repolarization and abnormal LV diastolic electromechanical discoordination exist in parallel in children with PAH and are associated with worse LV diastolic function and functional class.

Syncope during exercise: just another benign vasovagal event?

In general, syncope in children and adolescents is a benign event. Syncope during exercise may identify patients with a potentially fatal condition. Catecholaminergic polymorphic ventricular tachycardia is characterized by life-threatening ventricular arrhythmias, usually polymorphic ventricular tachycardia or ventricular fibrillation, occurring under conditions of exercise or emotional stress. Catecholaminergic polymorphic ventricular tachycardia is a familial condition that presents with exercise-induced syncope or sudden death in children or young adults. Detailed evaluation should be considered for patients who have syncope during exercise, injure themselves during the fall (i.e., unprotected faint with no antecedent warning prodrome), or who have a family history of syncope, early sudden cardiac death, myocardial disease, or arrhythmias.