Mitral Annular Disjunction: An Under-Recognized Entity in Pediatrics.

Mitral annular disjunction (MAD) is a rare and under-recognized entity in the pediatric population. We present 2 cases of MAD in previously healthy pediatric patients and highlight clinical scenarios where MAD should be suspected.

Multicenter retrospective evaluation of magnetic resonance imaging in pediatric and congenital heart disease patients with cardiac implantable electronic devices.

BACKGROUND: Guidelines addressing magnetic resonance imaging (MRI) in patients with cardiac implantable electronic devices (CIEDs) provide algorithms for imaging pediatric and congenital heart disease (CHD) patients. Guideline acceptance varies by institution. Guidelines also do not support routine MRI scans in patients with epicardial or abandoned leads, common in pediatric and CHD patients. OBJECTIVE: The purpose of this study was to determine the incidence of MRI-related complications in pediatric and CHD patients with CIEDs, including epicardial and/or abandoned leads. METHODS: A multicenter retrospective review included patients with CIEDs who underwent any MRI between 2007 and 2022 at congenital cardiac centers. The primary outcome was any patient adverse event or clinically significant CIED change after MRI, defined as pacing lead capture threshold increase >0.5 V with output change, P- or R- wave amplitude decrease >50% with sensitivity change, or impedance change >50%. RESULTS: Across 14 institutions, 314 patients (median age 18.8 [1.3; 31.4] years) underwent 389 MRIs. There were 288 pacemakers (74%) and 87 implantable cardioverter-defibrillators (22%); 52% contained epicardial leads, and 14 (4%) were abandoned leads only. Symptoms or CIED changes occurred in 4.9% of MRI scans (6.1% of patients). On 9 occasions (2%), warmth or pain occurred. Pacing capture threshold or lead impedance changes occurred in 1.4% and 2.0% of CIEDs post-MRI and at follow-up. CONCLUSION: Our data provide evidence that MRIs can be performed in pediatric and CHD patients with CIEDs, including non-MRI-conditional CIEDs and epicardial and/or abandoned leads, with rare minor symptoms or CIED changes but no other complications.

Validation of a novel automated signal analysis tool for ablation of Wolff-Parkinson-White Syndrome.

BACKGROUND: In previous pilot work we demonstrated that a novel automated signal analysis tool could accurately identify successful ablation sites during Wolff-Parkinson-White (WPW) ablation at a single center. OBJECTIVE: We sought to validate and refine this signal analysis tool in a larger multi-center cohort of children with WPW. METHODS: A retrospective review was performed of signal data from children with WPW who underwent ablation at two pediatric arrhythmia centers from 2008-2015. All patients with WPW ≤ 21 years who underwent invasive electrophysiology study and ablation with ablation signals available for review were included. Signals were excluded if temperature or power delivery was inadequate or lesion time was < 5 seconds. Ablation lesions were reviewed for each patient. Signals were classified as successful if there was loss of antegrade and retrograde accessory pathway (AP) conduction or unsuccessful if ablation did not eliminate AP conduction. Custom signal analysis software analyzed intracardiac electrograms for amplitudes, high and low frequency components, integrated area, and signal timing components to create a signal score. We validated the previously published signal score threshold 3.1 in this larger, more diverse cohort and explored additional scoring options. Logistic regression with lasso regularization using Youden's index criterion and a cost-benefit criterion to identify thresholds was considered as a refinement to this score. RESULTS: 347 signals (141 successful, 206 unsuccessful) in 144 pts were analyzed [mean age 13.2 ± 3.9 years, 96 (67%) male, 66 (45%) left sided APs]. The software correctly identified the signals as successful or unsuccessful in 276/347 (80%) at a threshold of 3.1. The performance of other thresholds did not significantly improve the predictive ability. A signal score threshold of 3.1 provided the following diagnostic accuracy for distinguishing a successful from unsuccessful signal: sensitivity 83%, specificity 77%, PPV 71%, NPV 87%. CONCLUSIONS: An automated signal analysis software tool reliably distinguished successful versus unsuccessful ablation electrograms in children with WPW when validated in a large, diverse cohort. Refining the tools using an alternative threshold and statistical method did not improve the original signal score at a threshold of 3.1. This software was effective across two centers and multiple operators and may be an effective tool for ablation of WPW.

Bridge to success: A better method of cryoablation for atrioventricular nodal reentrant tachycardia in children.

BACKGROUND: Cryoablation for atrioventricular nodal reentrant tachycardia (AVNRT) is associated with higher recurrence rates than radiofrequency ablation (RFA). Junctional tachycardia marks procedural success with RFA, but no such indicator exists for cryoablation. OBJECTIVE: The purpose of this study as to determine the impact of voltage mapping plus longer ablation lesions on midterm success of cryoablation for children with AVNRT. METHODS: We performed a single-center retrospective analysis of pediatric patients with AVNRT who underwent cryoablation from 2011 to 2015. Patients ablated using a standard electroanatomic approach (control) were compared with patients ablated using voltage mapping (voltage group). In the voltage group, EnSite NavX navigation and visualization technology (St Jude Medical, St Paul, MN) was used to develop a "bridge" of lower voltage gradients (0.3-0.8 mV) of the posteroseptal right atrium to guide cryoablation. Kaplan-Meier analysis was used to determine freedom from recurrence of supraventricular tachycardia. RESULTS: In all, 122 patients were included (71 voltage, 51 control). There was no difference between groups regarding age, sex, or catheter-tip size. Short-term success was similar in both groups (98.5% voltage vs 92% control; P = .159), but recurrence rates were lower in the voltage group (0% vs 11%, P = .006). Follow-up time was shorter in the voltage group (15 ± 7 months vs 22 ± 17 months, P < .05). The 1-year freedom from recurrence was lower in the voltage group (100% vs 91.5%, P <.05). Ablation times were longer in the voltage group (43.7 ± 20.9 minutes vs 34.3 ± 20.5 minutes, P = .01), but overall procedure times were shorter in the voltage group (157 ± 40 minutes vs 198 ± 133 minutes; P = .018). No significant complication was seen in either group. CONCLUSION: Voltage gradient mapping and longer lesion time can decrease recurrence rates in pediatric patients with AVNRT.

Ventricular pacing in single ventricles-A bad combination.

BACKGROUND: Chronic ventricular pacing (VP) is associated with systolic dysfunction in a subset of pediatric patients with heart block and structurally normal hearts. The effect of chronic VP in congenital heart disease is less well understood, specifically in the single-ventricle (SV) population. OBJECTIVE: To determine the longitudinal effect of VP in SV patients. METHODS: SV patients with heart block and dual-chamber pacemakers requiring >50% VP were compared with nonpaced (controls) SV patients matched for age, sex, and SV morphology. Patients were excluded if a prepacing echocardiogram was not available. Echocardiogram and clinical parameters were compared at baseline (prepacing) and at last follow-up in the paced group, and in controls when they were at ages similar to those of their paced-group matches. RESULTS: Twenty-two paced and 53 control patients from 2 institutions were followed for similar durations (6.6±5 years vs 7.6±7.6 years; P = .59). There was no difference between groups regarding baseline ventricular function or the presence of moderate-to-severe atrioventricular valvar regurgitation (AVVR). Paced patients were more likely to develop moderate-to-severe systolic dysfunction (68% vs 15%; P < .01) and AVVR (55% vs 8%; P < .001) and require heart failure medications (65% vs 21%; P < .001). Chronic VP was also associated with a higher risk of transplantation or death (odds ratio, 4.9; 95% confidence interval, 1.05-22.7; P = .04). CONCLUSIONS: SV patients requiring chronic VP are at higher risk of developing moderate-to-severe ventricular dysfunction and AVVR with an increased risk of death or transplantation compared with controls. New strategies to either limit VP or improve synchronization in this vulnerable population is imperative.

Circadian Variation of Ventricular Arrhythmias in Catecholaminergic Polymorphic Ventricular Tachycardia.

OBJECTIVES: The aim of this paper was to investigate whether ventricular arrhythmias in children with catecholaminergic polymorphic ventricular tachycardia (CPVT) show circadian patterns. BACKGROUND: Circadian arrhythmic patterns have been established in long QT, Brugada, and early repolarization, but have not been investigated in CPVT. METHODS: This is a multicenter, retrospective review of pediatric CPVT patients, age <21 years at diagnosis. Timing of ventricular tachycardia (VT ≥3 beats) was assessed during 24-h continuous monitoring (Holter, implantable loop recorder, implantable cardioverter defibrillator) and by eliminating sleep hours, in addition to sporadic exercise stress tests. Morning was defined as 6:00 am to 11:59 am, afternoon 12:00 pm to 5:59 pm, and evening 6:00 pm to 11:59 pm. Distribution of VT events was compared by time of day, day of week, age, and sex. RESULTS: Eighty patients (53% male), 61% with an ICD, experienced 423 VT events during a median follow-up time of 6 years (interquartile range: 2 to 10 years). When compared to morning hours, VT was more likely to occur in the afternoon (odds ratio [OR]: 2.54; 95% confidence interval [CI]: 1.69 to 3.83) or evening hours (OR: 2.91; 95% CI: 1.82 to 4.67). The predominance of afternoon/evening events persisted regardless of age, gender, or day of the week. Among 50 patients who underwent exercise stress tests, VT was significantly more likely to occur in the afternoon (OR: 3.00; 95% CI: 1.39 to 6.48). CONCLUSIONS: In pediatric CPVT patients, ventricular arrhythmias are more likely to occur in the afternoon and evening hours. Because children's activity levels peak in both the morning and afternoon, the lack of arrhythmias in the morning hours raises questions whether factors other than adrenergic stimulation influence arrhythmia induction in pediatric patients with CPVT.

Is There a Difference in Tachycardia Cycle Length during SVT in Children with AVRT and AVNRT?

BACKGROUND: There are limited adult data suggesting the tachycardia cycle length (TCL) of atrioventricular reentry tachycardia (AVRT) is shorter than atrioventricular nodal reentry tachycardia (AVNRT), though little data exist in children. We sought to determine if there is a difference in TCL between AVRT and AVNRT in children. METHODS: A single-center retrospective review of children with supraventricular tachycardia (SVT) from 2000 to 2015 was performed. INCLUSION CRITERIA: Age ≤ 18 years, invasive electrophysiology study (EPS) confirming AVRT or AVNRT. EXCLUSION CRITERIA: Atypical AVNRT, congenital heart disease, antiarrhythmic medication use at time of EPS. Data were compared between patients with AVRT and AVNRT via t-test, χ2 test, and linear regression. RESULTS: A total of 835 patients were included (12 ± 4 years, 52 ± 31 kg, TCL 321 ± 55 ms), 539 (65%) with AVRT (270 Wolff-Parkinson-White, 269 concealed pathways) and 296 (35%) with AVNRT. Patients with AVRT were younger (11.7 ± 4.1 years vs 13.0 ± 3.6 years, P < 0.001) and smaller (49 ± 22 kg vs 57 ± 43 kg, P < 0.001). In the baseline state, the TCL was shorter in AVRT than AVRNT (329 ± 51 ms vs 340 ± 60 ms, P = 0.04). In patients requiring isoproterenol to induce SVT, there was no difference in TCL (290 ± 49 ms vs 297 ± 49 ms, P = 0.26). When controlling for age, there was no difference in TCL between AVRT and AVNRT at baseline or on isoproterenol. The regression equation for TCL in the baseline state was TCL = 290 + 4 (age), indicating the TCL will increase by 4 ms above a baseline of 290 ms for each year of life. CONCLUSIONS: When controlling for age, there is no difference in the TCL between AVRT and AVNRT in children. Age, not tachycardia mechanism, is the most significant factor in predicting TCL.

Electrocardiographic repolarization abnormalities and increased risk of life-threatening arrhythmias in children with dilated cardiomyopathy.

BACKGROUND: Life-threatening arrhythmia events (LTEs) occur in ~5% of children with dilated cardiomyopathy (DCM). While prolonged QRS duration has been shown to be associated with LTEs, electrocardiographic (ECG) repolarization findings have not been examined. OBJECTIVE: We sought to determine the associations between ECG repolarization abnormalities and LTEs in children with DCM. METHODS: A single-center retrospective review of children with DCM was performed. LTEs were defined as documented ventricular tachycardia or fibrillation requiring medical intervention. Three pediatric cardiologists, blinded to clinical events, evaluated ECGs obtained at the time of initial referral. Kaplan-Meier survival and Cox proportional hazards analyses were used to evaluate time to LTEs. RESULTS: A total of 137 patients (mean age 7.8 ± 6.7 years; 75(55%) male patients) with DCM (mean ejection fraction 35% ± 16%) were included; 67 patients (49%) had a corrected JT (JTc) interval of ≥340 ms, 72 (53%) had a corrected QT (QTc) interval of ≥450 ms, and 41 (30%) had abnormal T waves. LTEs occurred in 15 patients at a median of 12 months (interquartile range 3-36 months) after the initial ECG. Patients with LTEs had a longer JTc interval (371 ± 77 ms vs 342 ± 41 ms; P = .02) and a longer QTc interval (488 ± 96 ms vs 453 ± 44 ms; P = .01). In survival analysis, a JTc interval of ≥390 ms (hazard ratio [HR] 4.07; 95% confidence interval [CI] 1.12-14.83; P = .03), a QTc interval of ≥510 ms (HR 6.95; 95% CI 1.53-31.49; P = .01), abnormal T-wave inversion (HR 11.62; 95% CI 2.75-49.00; P = .001), and ST-segment depression (HR 6.91; 95% CI 1.25-38.27; P = .03) were associated with an increased risk of LTEs, even after adjusting for QRS duration and amiodarone use. CONCLUSION: Repolarization abnormalities are common in children with DCM. Certain ECG repolarization abnormalities, such as significantly prolonged JTc and QTc intervals, may be useful in identifying patients at risk of LTEs.

Endomyocardial fibrosis and mural thrombus in a 4-year-old girl due to idiopathic hypereosinophilia syndrome described with serial cardiac magnetic resonance imaging.

We present the case of a 4-year-old girl with idiopathic hypereosinophilia syndrome, endomyocardial fibrosis, and mural thrombus. This condition is rarely seen in children outside the tropics. Myocardial biopsy is historically the standard for diagnosis. Reports in adult literature, however, have shown the utility of cardiac MRI as a non-invasive tool for diagnosis, prognosis, and monitoring. To our knowledge, this is the first reported case with serial cardiac MRI in a child.

50 is the new 70: Short ventriculoatrial times are common in children with atrioventricular reciprocating tachycardia.

BACKGROUND: One of the basic electrophysiological principles of atrioventricular reciprocating tachycardia (AVRT) is that ventriculoatrial (VA) times during tachycardia are >70 ms. We hypothesized, however, that children may commonly have VA times <70 ms in AVRT. OBJECTIVE: This study sought to determine the incidence and characteristics associated with short-VA AVRT in children. METHODS: A retrospective single-center review of children with AVRT from 2000 to 2014 was performed. All patients ≤18 years of age with AVRT at electrophysiology study were included. Patients with persistent junctional reciprocating tachycardia, atrioventricular nodal reentry tachycardia, and tachycardia not unequivocally proven to be AVRT were excluded. VA time was defined as the time between earliest ventricular activation and earliest atrial activation in any lead and was confirmed by 2 electrophysiologists. Patients with VA times <70 ms (SHORT-VA) and those with standard VA times ≥70 ms (STD-VA) were compared. Logistic regression analysis identified characteristics of SHORT-VA patients. RESULTS: A total of 495 patients with AVRT were included (mean age 11.7 ± 4.1 years). There were 265 patients (54%) with concealed accessory pathways (APs) and 230 (46%) with Wolff-Parkinson-White syndrome. AP location was left-sided in 301 patients (61%) and right-sided in 194 (39%). The mean VA time in AVRT was 100 ± 33 ms. A total of 63 patients (13%) had VA times <70 ms (SHORT-VA). The shortest VA time during AVRT was 50 ms. There was no difference in age, AV nodal block cycle, or body surface area between SHORT-VA and STD-VA patients, but SHORT-VA patients had lower weight (43 ± 17 vs 51 ± 23 kg, P = .02), lower AV nodal effective refractory period (AVNERP; 269 ± 50 vs 245 ± 52 ms, P < .01), and more left-sided APs (50 [79%] vs 251 [58%]; P < .01]. On multivariate logistic regression, factors associated with SHORT-VA included left-sided AP (odds ratio [OR] 5.79, confidence interval [95% CI] 2.21-15.1, P < .01), shorter AVNERP (OR 0.99, CI 0.98-0.99, P < .01), and lower weight (OR 0.97, CI 0.95-0.99, P < .01). CONCLUSIONS: Children with AVRT can frequently have VA times <70 ms, with 50 ms being the shortest VA time. This finding debunks the classic electrophysiology principle that VA times in AVRT must be >70 ms. SHORT-VA AVRT was more common in children with left-sided APs.

Ventricular lead redundancy to prevent cardiovascular events and sudden death from lead fracture in pacemaker-dependent children.

BACKGROUND: Children requiring a permanent epicardial pacemaker (PM) traditionally have a single lead placed on the right ventricle. Lead failure in pacemaker-dependent (PMD) children, however, can result in cardiovascular events (CVEs) and death. OBJECTIVE: The purpose of this study was to determine if redundant ventricular lead systems (RVLS) can safeguard against CVE and death in PMD children. METHODS: This was a single-center study of PMD patients undergoing placement of RVLS from 2002-2013. Patients ≤21 years of age who were PMD were included. Patients with a biventricular (BiV) system placed for standard resynchronization indications were excluded. RVLS patients were compared to PMD patients with only a single pacing lead on the ventricle (SiV). RESULTS: Seven hundred sixty-nine patients underwent PM/implantable cardioverter-defibrillator placement with 76 BiV implants; 49 patients (6%) were PMD. Thirteen patients underwent implantation of an RVLS. There was no difference between the RVLS group (n = 13) and SiV PMD control group (n = 24) with regard to age (RVLS 9.5 ± 5.8 years vs SiV 9.4 ± 6.7 years, P = .52), weight (RVLS 38.2 ± 32.6 kg vs SiV 35.2 ± 29.3 kg, P = .62), indication for pacing, procedural complications, or time to follow-up. There were 2 lead fractures (17%) in the RVLS group (mean follow-up 3.8 ± 2.9 years), with no deaths or presentations with CVE. The SiV control group had 3 lead fractures (13%) (mean follow-up 2.8 ± 2.9 years), with no deaths, but all 3 patients presented with CVE and required emergent PM placement. CONCLUSION: RVLS systems should be considered in children who are PMD and require permanent epicardial pacing. BiV pacing and RVLS may decrease the risk of CVE in the event of lead failure in PMD patients.

Efficacy of implantable cardioverter defibrillators in young patients with catecholaminergic polymorphic ventricular tachycardia: success depends on substrate.

BACKGROUND: The effectiveness of implantable cardioverter-defibrillator (ICD) therapy for the management of catecholaminergic polymorphic ventricular tachycardia (VT) in young patients is not known. ICD discharges are not always effective and inappropriate discharges are common, both resulting in morbidity and mortality. METHODS AND RESULTS: This is a multicenter, retrospective review of young patients with catecholaminergic polymorphic VT and ICDs from 5 centers. ICD discharges were evaluated to determine arrhythmia mechanism, appropriateness, efficacy of therapy, and complications. A total of 24 patients were included. Median (interquartile range) ages at onset of catecholaminergic polymorphic VT symptoms and ICD implant were 10.6 (5.0-13.8) years and 13.7 (10.7-16.3) years, respectively. Fourteen patients received 140 shocks. Ten patients (42%) experienced 75 appropriate shocks and 11 patients (46%) received 65 inappropriate shocks. On actuarial analysis, freedom from appropriate shock at 1 year after ICD implant was 75%. Of appropriate shocks, only 43 (57%) demonstrated successful primary termination. All successful appropriate ICD discharges were for ventricular fibrillation. No episodes of polymorphic VT or bidirectional VT demonstrated successful primary termination. The adjusted mean (95% confidence interval) cycle length of successful discharges was significantly shorter than unsuccessful discharges (168 [152-184] ms versus 245 [229-262] ms; adjusted P=0.002). Electrical storm occurred in 29% (4/14) and induction of more malignant ventricular arrhythmias in 36% (5/14). There were no deaths. CONCLUSIONS: ICD efficacy in catecholaminergic polymorphic VT depends on arrhythmia mechanism. Episodes of ventricular fibrillation were uniformly successfully treated, whereas polymorphic and bidirectional VT did not demonstrate successful primary termination. Inappropriate shocks, electrical storm, and ICD complications were common.

Catecholaminergic polymorphic ventricular tachycardia found in an adolescent after a methylenedioxymethamphetamine and marijuana-induced cardiac arrest.

OBJECTIVE: To illustrate the challenges of managing patients with acute, undiagnosed arrhythmias through a case that demonstrates a possible association between catecholaminergic polymorphic ventricular tachycardia, a genetically determined severe arrhythmia disorder that often presents as either syncope or sudden death, and 3,4-Methylenedioxymethamphetamine ("Ecstasy") combined with marijuana, which are often considered safe drugs by users. DESIGN: Case report. SETTING: Pediatric intensive care unit. PATIENT: A 15-yr-old male collapsed suddenly after ingesting an unknown substance and smoking marijuana. He was successfully resuscitated by first-responder chest compressions and rescue breaths along with a single 100-J shock by paramedics. He was intubated and transferred to a pediatric intensive care unit. Initial cardiac workup was negative but severe instability on vasopressors and a family history of intermittent palpitations and syncope in his brother raised suspicion for catecholaminergic polymorphic ventricular tachycardia. Identification of the unknown substance required coordination with a toxicology laboratory. INTERVENTIONS: The patient had extremely labile cardiovascular responses to vasopressors. On day 5, his blood pressure was stable and he was extubated. A full cardiac workup, including a catheterization (preadmission to pediatric intensive care unit), electrocardiogram, cardiac magnetic resonance imaging were done to screen out most structural arrythmogenic diseases. A specific genetic test for catecholaminergic polymorphic ventricular tachycardia was sent. MEASUREMENTS AND MAIN RESULTS: The patient's methylenedioxymethamphetamine blood level was 87 ng/mL approximately 12 hrs after ingestion. Given the 3-8 hr half-life of methylenedioxymethamphetamine, it is likely that levels were toxic at the time of ingestion (>110 ng/mL). Marijuana may have provided a synergistic critical catecholamine release to trigger an arrhythmia. Genetic testing showed a ryanodine receptor-2 mutation that was consistent with catecholaminergic polymorphic ventricular tachycardia. CONCLUSIONS: While an initial cardiac workup for an acute, undiagnosed arrhythmia may be negative, family history may be a simple, essential component of patient management and disease diagnosis. This case demonstrates a possible association between methylenedioxymethamphetamine, marijuana, and catecholaminergic polymorphic ventricular tachycardia. All genetic and structural arrythmogenic disorders should be considered when working up a patient with presumed toxin-induced arrhythmias.

Are wide complex tachycardia algorithms applicable in children and patients with congenital heart disease?

INTRODUCTION: Several algorithms have been developed to help determine the etiology of wide complex tachycardias (WCTs) in adults. Sensitivity and specificity for differentiating supraventricular tachycardia (SVT) with aberration from ventricular tachycardia (VT) in adults have been demonstrated to be as high as 98% and 97%. These algorithms have not been tested in the pediatric population. We hypothesize that these algorithms have lower diagnostic accuracy in children and patients with congenital heart disease. METHODS: A retrospective review of the pediatric electrophysiology database at Stanford from 2001 to 2008 was performed. All children with WCT, a 12-lead electrocardiogram (ECG) available for review, and an electrophysiology study confirming the etiology of the rhythm were included. Patients with a paced rhythm were excluded. The ECGs were analyzed by 2 electrophysiologists blinded to the diagnosis according to the algorithms described in Brugada et al,(2) and Vereckei et al.(5) Additional ECG findings were recorded by each electrophysiologist. RESULTS: A total of 65 WCT ECGs in 58 patients were identified. Supraventricular tachycardia was noted in 62% (40/65) and VT in 38% (25/65) of the ECGs. The mean age was 13.5 years (SD ± 5.1), the mean weight was 51.8 kg (SD ± 22.4), and 48% (31/65) were male. The mean tachycardia cycle length was 340 milliseconds (SD ± 95). Congenital heart disease (CHD) was present in 37% (24/65) of patients (7 tetralogy of Fallot, 6 Ebstein's, 4 double-outlet right ventricle, 3 complex CHD, 2 d-transposition of great arteries, 1 status-post orthotopic heart transplantation, 1 ventricular septal defect). The Brugada algorithm correctly predicted the diagnosis 69% (45/65) of the time, the Vereckei algorithm correctly predicted the diagnosis 66% (43/65) of the time, and the blinded reviewer correctly predicted the diagnosis 78% (51/65) of the time. There was no difference in the efficacy of the algorithms in patients with CHD vs those with structurally normal hearts. The findings of left superior axis deviation (P < .01) and a notch in the QRS downstroke of V(1) or V(2) (P < .01) were more common in VT than SVT, whereas a positive QRS deflection in V(1) (P = .03) was more commonly present in SVT than VT. CONCLUSION: The Brugada and Vereckei algorithms have lower diagnostic accuracy in the pediatric population and in patients with congenital heart disease than in the adult population. Left superior axis deviation and a notch in the QRS downstroke were more commonly associated with VT, whereas a positive QRS deflection in V(1) was more commonly associated with SVT in this population.

Cryoablation with an 8-mm tip catheter for pediatric atrioventricular nodal reentrant tachycardia is safe and efficacious with a low incidence of recurrence.

BACKGROUND: Cryoablation with 4- and 6-mm tip ablation catheters has been demonstrated to be safe and effective in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT) in pediatric patients, albeit with a higher rate of clinical recurrence. Limited information is available regarding efficacy, mid-term outcomes, and complications related to the use of the 8-mm Freezor Max Cryoablation catheter (Medtronic, Minneapolis, MN, USA) in pediatric patients. METHODS: We performed a retrospective review of all pediatric patients with normal cardiac anatomy who underwent an ablation procedure for treatment of AVNRT using the 8-mm tip Cryoablation catheter at three large pediatric academic arrhythmia centers. RESULTS: Cryoablation with an 8-mm tip catheter was performed in 77 patients for treatment of AVNRT (female n = 40 [52%], age 14.8 +/- 2.2 years, weight 62.0 +/- 13.9 kg). Initial procedural success was achieved in 69 patients (69/76, 91%). Transient second- or third-degree atrioventricular (AV) block was noted in five patients (6.5%). There was no permanent AV block. Of the patients successfully ablated with Cryotherapy, there were two recurrences (2/70, 2.8%) over a follow-up of 11.6 +/- 3.3 months. CONCLUSION: Cryoablation with an 8-mm tip ablation catheter is both safe and effective with a low risk of recurrence for the treatment of AVNRT in pediatric patients.

Cryoablation for atrioventricular nodal reentrant tachycardia in young patients: predictors of recurrence.

BACKGROUND: Recurrence rates of atrioventricular nodal reentry tachycardia (AVNRT) after cryoablation continue to remain high despite excellent initial success rates. Our objective was to evaluate the clinical outcomes of cryoablation for AVNRT with the 4-mm and 6-mm tip cryoablation catheters in a young population and to elicit predictors of arrhythmia recurrence. METHODS: We retrospectively reviewed all patients who underwent cryoablation for AVNRT at the UCSF/Stanford Pediatric Arrhythmia Center from January 2004 to February 2007. RESULTS: One hundred fifty-four patients (age 13.7 years (3.2-24.4)) underwent cryoablation for AVNRT of which 144 patients had inducible AVNRT (123 sustained and 21 nonsustained) and 10 had presumed AVNRT. Initial success was achieved in 95% (146/154), with no difference between the 4-mm (93%) and 6-mm (98%) cryoablation catheter tips (P = 0.15). There was no permanent atrioventricular (AV) block. Transient third-degree AV block occurred in nine patients (6%), with no difference between the 4-mm (4%) and 6-mm (9%) tip (P = 0.13). AVNRT recurrence was documented in 14% in a median time of 2.5 months (0.25-20). Recurrences were lower with the 6-mm (9%) versus the 4-mm (18%) tip, but this did not reach statistical significance (P = 0.16). With univariate analysis, a longer fluoroscopy time was the only significant factor associated with recurrence. Multivariate analysis failed to identify any significant predictor of AVNRT recurrence. CONCLUSION: Outcomes of cryoablation for AVNRT continue to be good without the complication of AV block. We could not identify any specific parameter associated with AVNRT recurrence. Further improvements in cryoablation technique will be necessary to reduce recurrences.

Cryoablation versus radiofrequency ablation for treatment of pediatric atrioventricular nodal reentrant tachycardia: initial experience with 4-mm cryocatheter.

BACKGROUND: Initial reports have shown cryoablation to be safe and efficacious for treatment of atrioventricular nodal reentrant tachycardia (AVNRT). No direct comparisons of cryoablation vs radiofrequency (RF) catheter ablation in pediatric patients have been made. OBJECTIVES: The purpose of this study was to compare the outcomes of cryothermal vs RF catheter ablation for treatment of AVNRT in pediatric patients. METHODS: We retrospectively reviewed consecutive ablation procedures for treatment of AVNRT at a single arrhythmia center. The RF group consisted of patients who underwent RF ablation from 2002 until cryothermy became available. The cryoablation group consisted of patients who underwent cryothermal ablation from 2004 to 2005. The groups were compared for procedural and electrophysiologic outcomes. RESULTS: RF (n = 60, age 14 +/- 4 years) and cryoablation (n = 57, age 14 +/- 4 years) groups had similar demographic and baseline parameters. Procedural times were shorter in the RF group (RF ablation 112 +/- 31 minutes vs cryoablation 148 +/- 46 minutes, P < .001). Fluoroscopy times were comparable (RF ablation 21 +/- 15 minutes vs cryoablation 20 +/- 13 minutes, P = .77). In an intention-to-treat analysis, success of the procedure was 100% for RF ablation and 95% for cryoablation (P = .11). No permanent AV block occurred in either group. Recurrence rates were higher for the cryoablation group, but this did not reach statistical significance (RF ablation 2% vs cryoablation 8%, P = .19). CONCLUSION: Cryoablation appears to be similar to RF for ablation of AVNRT with respect to short-term efficacy and safety of the procedure in a pediatric population. Recurrence rates are higher with cryoablation.

Utility of Holter electrocardiogram in iron-overloaded hemoglobinopathies.

Cardiac arrhythmias are among the leading causes of morbidity and mortality of transfusion-dependent, iron-overloaded beta-thalassemia patients. Routine screening with Holter electrocardiogram has been recommended; however, infrequent electrocardiographic changes limit its clinical usefulness. The purpose of this study was to determine the diagnostic yield of Holter electrocardiogram monitoring and its correlation with patient symptoms and disease status. A retrospective analysis was performed on 27 transfusion-dependent thalassemia patients who underwent cardiac questionnaire and Holter screening yearly, in addition to echocardiogram and quantitative iron-level determination. Four patients had clinically significant arrhythmias detected on Holter screening, while 2 patients developed severe cardiac complications secondary to arrhythmias within 1 year of follow-up of normal Holter screening. Early detection of cardiac events among transfusion-dependent thalassemia patients with Holter electrocardiography is not clinically effective. Other screening modalities, including the transtelephonic event recorder, should be evaluated in arrhythmia surveillance.