Intracardiac echocardiography in paediatric and congenital cardiac ablation shortens procedure duration and improves success without complications.

AIMS: Common to adult electrophysiology studies (EPSs), intracardiac echocardiography (ICE) use in paediatric and congenital heart disease (CHD) EPS is limited. The purpose of this study was to assess the efficacy of ICE use and incidence of associated complications in paediatric and CHD EPS. METHODS AND RESULTS: This single-centre retrospective matched cohort study reviewed EPS between 2013 and 2022. Demographics, CHD type, and EPS data were collected. Intracardiac echocardiography cases were matched 1:1 to no ICE controls to assess differences in complications, ablation success, fluoroscopy exposure, procedure duration, and arrhythmia recurrence. Cases and controls with preceding EPS within 5 years were excluded. Intracardiac echocardiography cases without an appropriate match were excluded from comparative analyses but included in the descriptive cohort. We performed univariable and multivariable logistic regression to assess associations between variables and outcomes. A total of 335 EPS were reviewed, with ICE used in 196. The median age of ICE cases was 15 [interquartile range (IQR) 12-17; range 3-47] years, and median weight 57 [IQR 45-71; range 15-134] kg. There were no ICE-related acute or post-procedural complications. There were 139 ICE cases matched to no ICE controls. Baseline demographics and anthropometrics were similar between cases and controls. Fluoroscopy exposure (P = 0.02), procedure duration (P = 0.01), and arrhythmia recurrence (P = 0.01) were significantly lower in ICE cases. CONCLUSION: Intracardiac echocardiography in paediatric and CHD ablations is safe and reduces procedure duration, fluoroscopy exposure, and arrhythmia recurrence. However, not every arrhythmia substrate requires ICE use. Thoughtful selection will ensure the judicious and strategic application of ICE to enhance outcomes.

Limited Relationship Between Echocardiographic Measures and Electrocardiographic Markers of Left Ventricular Size in Healthy Children.

Pediatric ECG standards have been defined without echocardiographic confirmation of normal anatomy. The Pediatric Heart Network Normal Echocardiogram Z-score Project provides a racially diverse group of healthy children with normal echocardiograms. We hypothesized that ECG and echocardiographic measures of left ventricular (LV) dimensions are sufficiently correlated in healthy children to imply a clinically meaningful relationship. This was a secondary analysis of a previously described cohort including 2170 digital ECGs. The relationship between 6 ECG measures associated with LV size were analyzed with LV Mass (LVMass-z) and left ventricular end-diastolic volume (LVEDV-z) along with 11 additional parameters. Pearson or Spearman correlations were calculated for the 78 ECG-echocardiographic pairs with regression analyses assessing the variance in ECG measures explained by variation in LV dimensions and demographic variables. ECG/echocardiographic measurement correlations were significant and concordant in 41/78 (53%), though many were significant and discordant (13/78). Of the 6 ECG parameters, 5 correlated in the clinically predicted direction for LV Mass-z and LVEDV-z. Even when statistically significant, correlations were weak (0.05-0.24). R2 was higher for demographic variables than for echocardiographic measures or body surface area in all pairs, but remained weak (R2 ≤ 0.17). In a large cohort of healthy children, there was a positive association between echocardiographic measures of LV size and ECG measures of LVH. These correlations were weak and dependent on factors other than echocardiographic or patient derived variables. Thus, our data support deemphasizing the use of solitary, traditional measurement-based ECG markers traditionally thought to be characteristic of LVH as standalone indications for further cardiac evaluation of LVH in children and adolescents.

Ventricular arrhythmias following balloon-expandable transcatheter pulmonary valve replacement in the native right ventricular outflow tract.

BACKGROUND: Ventricular arrhythmia incidence in children and adolescents undergoing transcatheter pulmonary valve replacement (TPVR) within the native right ventricular outflow tract (nRVOT) is unknown. We sought to describe the incidence, severity, and duration of ventricular arrhythmias and identify associated risk factors in this population. METHODS: This was a retrospective cohort study of 78 patients <21 years of age who underwent TPVR within the nRVOT. Patients were excluded for pre-existing ventricular arrhythmia or antiarrhythmic use. Study variables included surgical history, valve replacement indication, valve type/size, and ventricular arrhythmia. Univariable logistic regression models were used to evaluate factors associated with ventricular arrhythmias, followed by subset analyses. RESULTS: Nonsustained ventricular arrhythmia occurred in 26/78 patients (33.3%). The median age at the procedure was 10.3 years (interquartle range [IQR]: 6.5, 12.8). Compared with other nRVOT types, surgical repair with transannular patch was protective against ventricular arrhythmia incidence: odds ratio (OR): 0.35 (95% confidence interval [CI], 0.13-0.95). Patient weight, valve type/size, number of prestents, and degree of stent extension into the RVOT were not associated with ventricular arrhythmia occurrence. Beta blocker was started in 16/26 (61.5%) patients with ventricular arrhythmia. One additional patient was lost to follow-up. The median beta blocker duration was 46 days (IQR 42, 102). Beta blocker was discontinued in 10 patients by 8-week follow-up and in the remaining four by 9 months. CONCLUSIONS: Though common after balloon-expandable TPVR within the nRVOT, ventricular arrhythmias were benign and transient. Antiarrhythmic medications were successfully discontinued in the majority at 6- to 8-week follow-up, and in all patients by 20 months.

The high-density grid catheter: A safe adjunctive tool in pediatric and complex congenital heart disease patients.

INTRODUCTION: The safety and utility of the Advisor™ High-Density Grid mapping catheter (HDGC) in children and congenital heart disease (CHD) patients are not well described. METHODS: A single-center retrospective cohort study of pediatric and CHD patients undergoing electrophysiology study and ablation to determine the effect of HDGC use on outcomes including complications, fluoroscopy use, procedure duration, acute ablation success, and arrhythmia recurrence. RESULTS: HDGC was used in 74/261 (28.3%) cases. HDGC subjects differed by median age (17 vs. 13 years; p < 0.001), weight (68 vs. 50 kg; p < 0.001), and prevalence of significant CHD (42% vs. 3%; p < 0.001). Arrhythmia substrates were dissimilar: HGDC cases had higher frequencies of intra-atrial re-entrant tachycardia (25.7% vs. 0.5%), atrial flutter (8.1% vs. 1.1%), ectopic atrial tachycardia (13.5% vs. 3.7%), and premature ventricular contractions (9.5% vs. 0.5%), and lower incidences of atrioventricular re-entrant tachycardia (16.2% vs. 46.1%). Complications were rare (n = 5, 1.9%) with no significant difference between groups (p = 1.00). Procedure duration-but not fluoroscopy exposure-was significantly longer in HDGC cases (median 256 vs. 216 min, p < 0.001). Acute success was lower (93.2% vs. 99.4%; p = 0.01) and recurrences higher (13.2% vs. 3.8%; p = 0.016) in HDGC compared to non-HDGC cases. CONCLUSION: HDGC use in children and CHD patients is safe and not associated with higher complication rates. The lower acute success and higher recurrence rates in HDGC cases likely reflect a bias toward HDGC use in more complex arrhythmia substrates rather than less favorable ablation outcomes.

MRI in pediatric and congenital heart disease patients with CIEDs and epicardial or abandoned leads.

BACKGROUND: Heart Rhythm Society guidelines outlining magnetic resonance imaging (MRI) in patients with cardiac implantable electronic devices (CIEDs) excluded children and epicardial or abandoned leads due to theoretical risks of harm. Research investigating these risks is lacking. The primary objective of our study is to determine the incidence of adverse events to patients or CIEDs from MRI imaging. The secondary objective is to describe CIED-related artifact on MRI images. METHODS: A single-center retrospective review was performed on all patients with CIEDs who underwent 1.5 Tesla MRI between July 2007 and May 2019. We subdivided patients among four cohorts: (1) patients <18 years of age, (2) epicardial leads, (3) abandoned endocardial leads, and (4) abandoned epicardial leads. Descriptive statistics pre- and post-MRI and at follow-up within 1.5 years were conducted. RESULTS: Fifty-four MRIs were performed on 40 patients. Median age was 21.2 years (IQR 12.0-25.0). Eighteen (33%) MRIs contained abandoned leads; 20 (37%) contained epicardial leads. Three patients, one with abandoned epicardial leads and two with abandoned endocardial leads, experienced mild discomfort at the CIED site. One adult with endocardial leads experienced a pause in the heart rate while programmed in a nonpacing mode. No clinically important changes to CIED parameters occurred. Nine MRIs (17%), especially those with functional cardiac imaging, were uninterpretable due to image artifact. CONCLUSION: In this study, pediatric and adult CHD patients with CIEDs, many with epicardial or abandoned leads, underwent MRIs without clinically significant complications. In some, CIED artifact reduced cardiac MRI image quality due to CIED position.

A Functional Assay for Sick Sinus Syndrome Genetic Variants.

BACKGROUND/AIMS: Congenital Sick Sinus Syndrome (SSS) is a disorder associated with sudden cardiac death due to severe bradycardia and prolonged pauses. Mutations in HCN4, the gene encoding inward Na+/K+ current (If), have been described as a cause of congenital SSS. The objective of this study is to develop an SSS model in embryonic zebrafish, and use zebrafish as a moderate-throughput assay to functionally characterize HCN4 variants. METHODS: To determine the function of hcn4 in zebrafish, embryos were either bathed in the If -specific blocker (ZD-7288), or endogenous hcn4 expression was knocked down using splice-blocking morpholinos. To assess whether the zebrafish model discriminates benign from pathogenic variants, we tested four HCN4 mutations known to cause human SSS and four variants of unknown significance (VUS). RESULTS: Pharmacological blockade and knockdown of hcn4 in zebrafish phenocopied human SSS, displaying bradycardia and cardiac pauses in intact embryos and explanted hearts. The zebrafish assay correctly identified all disease-causing variants. Of the VUS, the assay predicted 2 as benign and 2 as hypomorphic variants. CONCLUSIONS: We conclude that our embryonic zebrafish assay is a novel and effective tool to functionally characterize human HCN4 variants, which can be translated into important clinical prognostic information.

Lumenless pacing leads: performance and extraction in pediatrics and congenital heart disease.

BACKGROUND: Pediatric and congenital heart disease (CHD) patients requiring permanent pacing present unique challenges, including need for long duration of implant, small size, and structural abnormalities. We report 6 years of experience with a novel 4.1-Fr lumenless pacing lead (model 3830, Medtronic Inc., Minneapolis, MN, USA) in this population. METHODS: Retrospective review of M3830 leads implanted at a pediatric center from 2005 to 2011. Data were compared to a population with a conventional pacing lead (model 1488, St. Jude Medical Inc., St. Paul, MN, USA). RESULTS: A total of 193 patients with 198 model 3830 leads (125 atrial, 73 ventricular) were enrolled. CHD was present in 121 (63%). Age and weight at implant were 16.6 ± 8.5 years and 51.7 ± 23.5 kg, respectively. Length of follow-up was 26 ± 19 months (range 0-73). At implant, mean sensing and capture thresholds were good and remained stable over time. There were no significant differences in electrical performance compared to 101 leads in the comparison group. Implant complications were rare. Follow-up complications occurred in 4% of the M3830 leads and 16% of M1488 leads. Eleven M3830 leads required extraction. All were extracted without complications using only manual traction. There were three deaths in each group. One death in the M1488 group occurred during lead extraction. No other deaths were lead related. CONCLUSION: During up to 6 years of use in pediatric and CHD patients, the M3830 lead has demonstrated excellent efficacy, a low rate of complications, and straightforward extractability relative to traditional pacing leads.

Long-Term Outcomes of Cardiac Resynchronization Therapy in Patients With Repaired Tetralogy of Fallot: A Multicenter Study.

BACKGROUND: A growing number of patients with tetralogy of Fallot develop left ventricular systolic dysfunction and heart failure, in addition to right ventricular dysfunction. Although cardiac resynchronization therapy (CRT) is an established treatment option, the effect of CRT in this population is still not well defined. This study aimed to investigate the early and late efficacy, survival, and safety of CRT in patients with tetralogy of Fallot. METHODS: Data were analyzed from an observational, retrospective, multicenter cohort, initiated jointly by the Pediatric and Congenital Electrophysiology Society and the International Society of Adult Congenital Heart Disease. Twelve centers contributed baseline and longitudinal data, including vital status, left ventricular ejection fraction (LVEF), QRS duration, and NYHA functional class. Outcomes were analyzed at early (3 months), intermediate (1 year), and late follow-up (≥2 years) after CRT implantation. RESULTS: A total of 44 patients (40.3±19.2 years) with tetralogy of Fallot and CRT were enrolled. Twenty-nine (65.9%) patients had right ventricular pacing before CRT upgrade. The left ventricular ejection fraction improved from 32% [24%-44%] at baseline to 42% [32%-50%] at early follow-up (P<0.001) and remained improved from baseline thereafter (P≤0.002). The QRS duration decreased from 180 [160-205] ms at baseline to 152 [133-182] ms at early follow-up (P<0.001) and remained decreased at intermediate and late follow-up (P≤0.001). Patients with upgraded CRT had consistent improvement in left ventricular ejection fraction and QRS duration at each time point (P≤0.004). Patients had a significantly improved New York Heart Association functional class after CRT implantation at each time point compared with baseline (P≤0.002). The transplant-free survival rates at 3, 5, and 8 years after CRT implantation were 85%, 79%, and 73%. CONCLUSIONS: In patients with tetralogy of Fallot treated with CRT consistent improvement in QRS duration, left ventricular ejection fraction, New York Heart Association functional class, and reasonable long-term survival were observed. The findings from this multicenter study support the consideration of CRT in this unique population.

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.

Multicenter Outcomes of Catheter Ablation for Atrioventricular Reciprocating Tachycardia Mediated by Twin Atrioventricular Nodes.

OBJECTIVES: This study sought to describe the electrophysiologic properties and catheter ablation outcomes for atrioventricular reciprocating tacchycardia via twin atrioventricular nodes (T-AVRT). BACKGROUND: Although catheter ablation for T-AVRT is an established entity, there are few data on the electrophysiological properties and outcomes of this procedure. METHODS: An international, multicenter study was conducted to collect retrospective procedural and outcomes data for catheter ablation of T-AVRT. RESULTS: Fifty-nine patients with T-AVRT were identified (median age at procedure, 8 years [interquartile range: 4.4-17.0 years]; 49% male). Of these, 55 (93%) were diagnosed with heterotaxy syndrome (right atrial isomerism in 39, left atrial isomerism in 8, and indeterminate in 8). Twenty-three (39%) had undergone Fontan operation (12 extracardiac, 11 lateral tunnel). After the Fontan operation, atrial access was conduit or baffle puncture in 15 (65%), fenestration in 5 (22%), and retrograde in 3 (13%). Acute success was achieved in 43 (91%) of 47 attempts (targeting an anterior node in 23 and posterior node in 24). There was no high-grade AV block or change in QRS duration. Over a median of 3.8 years, there were 3 recurrences. Of 7 patients with failed index procedure or recurrent T-AVRT, 6 (86%) were associated with anatomical hurdles such as prior Fontan or catheter course through an interrupted inferior vena cava-to-azygous vein continuation (P = 0.11). CONCLUSIONS: T-AVRT can be targeted successfully with low risk for recurrence. Complications were rare in this population. Anatomical challenges were common among patients with reduced short and long-term efficacy, representing opportunities for improvement in procedural timing and planning.

Cardiac Resynchronization Therapy for Adult Patients With a Failing Systemic Right Ventricle: A Multicenter Study.

Background The objective of this international multicenter study was to investigate both early and late outcomes of cardiac resynchronization therapy (CRT) in patients with a systemic right ventricle (SRV) and to identify predictors for congestive heart failure readmissions and mortality. Methods and Results This retrospective international multicenter study included 13 centers. The study population comprised 80 adult patients with SRV (48.9% women) with a mean age of 45±14 (range, 18-77) years at initiation of CRT. Median follow-up time was 4.1 (25th-75th percentile, 1.3-8.3) years. Underlying congenital heart disease consisted of congenitally corrected transposition of the great arteries and dextro-transposition of the great arteries in 63 (78.8%) and 17 (21.3%) patients, respectively. CRT resulted in significant improvement in functional class (before CRT: III, 25th-75th percentile, II-III; after CRT: II, 25th-75th percentile, II-III; P=0.005) and QRS duration (before CRT: 176±27; after CRT: 150±24 milliseconds; P=0.003) in patients with pre-CRT ventricular pacing who underwent an upgrade to a CRT device (n=49). These improvements persisted during long-term follow-up with a marginal but significant increase in SRV function (before CRT; 30%, 25th-75th percentile, 25-35; after CRT: 31%, 25th-75th percentile, 21-38; P=0.049). In contrast, no beneficial change in the above-mentioned variables was observed in patients who underwent de novo CRT (n=31). A quarter of all patients were readmitted for heart failure during follow-up, and mortality at latest follow-up was 21.3%. Conclusions This international experience with CRT in patients with an SRV demonstrated that CRT in selected patients with SRV dysfunction and pacing-induced dyssynchrony yielded consistent improvement in QRS duration and New York Heart Association functional status, with a marginal increase in SRV function.

Somatic mosaicism contributes to phenotypic variation in Timothy syndrome.

Timothy syndrome type 1 (TS-1) is a rare disorder that affects multiple organ systems and has a high incidence of sudden death due to profound QT prolongation and resultant ventricular arrhythmias. All previously described cases of TS-1 are the result of a missense mutation in exon 8A (p.G406R), an alternatively spliced variant of the L-type calcium channel gene (Ca(v)1.2, CACNA1C). Most patients reported in the literature represent highly affected individuals who present early in life with severe cardiac and neurological manifestations. Here, we describe somatic mosaicism in TS-1 patients with less severe manifestations than the typical TS-1 patient. These findings suggest that the TS prognosis may not be as dismal as previously reported. Moreover, our findings have implications for genetic counseling in that previously described de novo TS mutations may represent cases of parental mosaicism and warrant careful genotyping of parental tissue other than peripheral blood lymphocytes.

Validating defibrillation simulation in a human-shaped phantom.

BACKGROUND: We previously developed a computational model to aid clinicians in positioning implantable cardioverter-defibrillators (ICDs), especially in the case of abnormal anatomies that commonly arise in pediatric cases. We have validated the model clinically on the body surface; however, validation within the volume of the heart is required to establish complete confidence in the model and improve its use in clinical settings. OBJECTIVE: The goal of this study was to use an animal model and thoracic phantom to record the ICD potential field within the heart and on the torso to validate our defibrillation simulation system. METHODS: We recorded defibrillator shock potentials from an ICD suspended together with an animal heart in a human-shaped torso tank and compared them with simulated values. We also compared the scaled distribution threshold, an analog to the defibrillation threshold, calculated from the measured and simulated electric fields within the myocardium. RESULTS: ICD potentials recorded on the tank and cardiac surface and within the myocardium agreed well with those predicted by the simulation. A quantitative comparison of the recorded and simulated potentials yielded a mean correlation of 0.94 and a relative error of 19.1%. The simulation can also predict scaled distribution thresholds similar to those calculated from the measured potential fields. CONCLUSION: We found that our simulation could predict potential fields with high correlation with the measured values within the heart and on the torso surface. These results support the use of this model for the optimization of ICD placements.

Permanent conduction system pacing for congenitally corrected transposition of the great arteries: A Pediatric and Congenital Electrophysiology Society (PACES)/International Society for Adult Congenital Heart Disease (ISACHD) Collaborative Study.

BACKGROUND: Congenitally corrected transposition of the great arteries (CCTGA) is associated with spontaneous atrioventricular block and pacing-induced cardiomyopathy. Conduction system pacing is a potential alternative to conventional cardiac resynchronization therapy (CRT). OBJECTIVE: The purpose of this study was to determine the outcomes of conduction system pacing for CCTGA. METHODS: Retrospective data were collected from 10 international centers. RESULTS: His bundle (HBP) or left bundle branch pacing (LBBP) was attempted in 15 CCTGA patients (median age 23 years; 87% male). Previous surgery had been performed in 8 and chronic ventricular pacing in 7. Conduction system pacing (11 HBP, 2 LBBP 2; nonselective in 10, selective in 3) was acutely successful in 13 (86%) without complication. In 9 cases, electroanatomic mapping was available and identified the distal His bundle and proximal left bundle branches within the morphologic left ventricle below the pulmonary valve separate from the mitral annulus. Median implant HV interval was 42 ms (interquartile range [IQR] 35-48), R wave 6 mV (IQR 5-18), and threshold 0.5 V (IQR 0.5-1.2) at median 0.5 ms. QRSd was unchanged compared to junctional escape rhythm (124 vs 110 ms; P = .17) and decreased significantly compared to baseline ventricular pacing (112 vs 164 ms; P <.01). At a median of 8 months, all patients were alive without significant change in pacing threshold or lead dysfunction. New York Heart Association functional class improved in 5 patients. CONCLUSION: Permanent conduction system pacing is feasible in CCTGA by either HBP or proximal LBBP. Narrow paced QRS and stable lead thresholds were observed at intermediate follow-up. Unique anatomic characteristics may favor this approach over conventional CRT.

Subcutaneous Implantable Cardioverter-Defibrillators in Pediatrics and Congenital Heart Disease: A Pediatric and Congenital Electrophysiology Society Multicenter Review.

OBJECTIVES: The primary goal of this study was to evaluate the implant experience and midterm results of subcutaneous implantable cardioverter-defibrillators (S-ICDs) in pediatric patients and those with congenital heart disease. BACKGROUND: The S-ICD was developed to avoid the lead-related complications associated with transvenous systems. The absence of intravascular or intracardiac components offers potential advantages to pediatric patients and those with congenital heart disease. METHODS: This international, multicenter, retrospective, standard-of-care study was conducted through the Pediatric & Congenital Electrophysiology Society. Complications at 30 and 360 days, inappropriate shocks, and delivery of appropriate therapy were assessed. RESULTS: The study included 115 patients with a median follow-up of 32 (19 to 52) months. Median age was 16.7 years (14.8 to 19.3 years), 29% were female, and 55% had a primary prevention indication. Underlying disease substrate was cardiomyopathy (40%), structural heart disease (32%), idiopathic ventricular fibrillation (16%), and channelopathy (13%). The complication rate was 7.8% at 30 days and 14.7% at 360 days. Overall, inappropriate shocks occurred in 15.6% of patients, with no single clinical characteristic reaching statistical significance. At implant, 97.9% of patients had successful first shock conversion with 96% requiring ≤65 J. Appropriate therapy was delivered to 11.2% of patients with an annual incidence of 3.9% and an acute first shock conversion success rate of 92.5%. CONCLUSIONS: This study found that in a heterogeneous population of pediatric patients and those with congenital heart disease, the S-ICD had comparable rates of complications, inappropriate shocks, and conversion efficacy compared with previously published studies on transvenous systems in similar populations.

Contrasting effects of convective flow on catheter ablation lesion size: cryo versus radiofrequency energy.

BACKGROUND: Cryoablation has now become an alternative to treat many cardiac arrhythmias, and may be the treatment of choice in some patient populations. We compared the effects of convective flow on large-tip cryo and radiofrequency (RF) lesions dimensions. METHODS: Cryoablation and RF ablation were performed on porcine heart sections in a saline bath with varying directed flow rates. Cryoablation was performed for 4 minutes on 50 tissue pieces with tip temperature controlled at -80 degrees C. RF ablation was performed on 50 tissue pieces for 60 seconds at 60 degrees C tip temperature. The pieces were placed in culture media for 24 hours, and then sectioned, stained, and measured. RESULTS: Cryoablation and RF lesion sizes varied significantly with flow such that higher flow rates produced smaller cryoablation lesions and larger RF lesions (mean cryoablation volumes: 854 +/- 402, 808 +/- 217, 781 +/- 217, 359 +/- 114, and 292 +/- 117 mm(3), and mean RF volumes: 211 +/- 35, 304 +/- 79, 439 +/- 125, 525 +/- 187, and 597 +/- 126 mm(3) for 0, 1, 2, 3, and 5 L/min flow rates, respectively, P < 0.0005). Trabeculated pieces had larger cryoablation lesions and smaller RF lesions than nontrabeculated ones at higher flow rate (P < 0.005). Cryoablation lesion volume increased as the time to reach -80 degrees C decreased (r(2)= 0.72). CONCLUSION: In contrast to RF ablation, cryoablation lesion size is smaller at high flow rates, and larger at low flow rates due to the warming effects of local convective flow. The effects of high flow are reduced in areas of trabeculation, and the time to reach -80 degrees C predicts cryoablation lesion size.

Measuring defibrillator surface potentials: The validation of a predictive defibrillation computer model.

Implantable cardioverter defibrillators (ICDs) are commonly used to reduce the risk in patients with life-threatening arrhythmias, however, clinicians have little systematic guidance to place the device, especially in cases of unusual anatomy. We have previously developed a computational model that evaluates the efficacy of a delivered shock as a clinical and research aid to guide ICD placement on a patient specific basis. We report here on progress to validate this model with measured ICD surface potential maps from patients undergoing ICD implantation and testing for defibrillation threshold (DFT). We obtained body surface potential maps of the defibrillation pulses by adapting a limited lead selection and potential estimation algorithm to deal with the limited space for recording electrodes. Comparison of the simulated and measured potential maps of the defibrillation shock yielded similar patterns, a typical correlation greater than 0.9, and a relative error less than 15%. Comparison of defibrillation thresholds also showed accurate prediction of the simulations. The high agreement of the potential maps and DFTs suggests that the predictive simulation generates realistic potential values and can accurately predict DFTs in patients. These validation results pave the way for use of this model in optimization studies prior to device implantation.

Frequency of Ventricular Arrhythmias and Other Rhythm Abnormalities in Children and Young Adults With the Marfan Syndrome.

Patients with the Marfan syndrome (MFS) are at risk for sudden death. The contribution of arrhythmias is unclear. This study examines the prevalence of arrhythmias in children with the MFS and their relation to clinical and/or echocardiographic factors. Data from the Pediatric Heart Network randomized trial of atenolol versus losartan in MFS were analyzed (6 months to 25 years old, aortic root diameter z-score > 3.0, no previous aortic surgery and/or dissection). Baseline 24-hour ambulatory electrocardiographic monitoring was performed. Significant ventricular ectopy (VE) and supraventricular ectopy (SVE) were defined as ≥10 VE or SVE/hour, or the presence of high-grade ectopy. Three-year composite clinical outcome of death, aortic dissection, or aortic root replacement was analyzed. There were 274 analyzable monitors on unique patients from 11 centers. Twenty subjects (7%) had significant VE, 13 (5%) significant SVE; of these, 2 (1%) had both. None had sustained ventricular or supraventricular tachycardia. VE was independently associated with increasing number of major Ghent criteria (odds ratio [OR] = 2.13/each additional criterion, p = 0.03) and greater left ventricular end-diastolic dimension z-score (OR = 1.47/each 1 unit increase in z-score, p = 0.01). SVE was independently associated with greater aortic sinotubular junction diameter z-score (OR = 1.56/each 1 unit increase in z-score, p = 0.03). The composite clinical outcome (14 events) was not related to VE or SVE (p ≥ 0.3), but was independently related to heart rate variability (higher triangular index). In conclusion, in this cohort, VE and SVE were rare. VE was related to larger BSA-adjusted left ventricular size. Routine ambulatory electrocardiographic monitoring may be useful for risk stratification in select MFS patients.