The Value of Programmed Ventricular Extrastimuli From the Right Ventricular Basal Septum During Supraventricular Tachycardia.

BACKGROUND: The difference between the right ventricular (RV) apical stimulus-atrial electrogram (SA) interval during resetting of supraventricular tachycardia (SVT) versus the ventriculoatrial (VA) interval during SVT (ΔSA-VAapex) is an established technique for discerning SVT mechanisms but is limited by a significant diagnostic overlap. OBJECTIVES: This study hypothesized that the difference between the RV SA interval during resetting of SVTs versus the VA interval during SVTs (ΔSA-VA) would yield a more robust differentiation of atrioventricular nodal re-entrant tachycardia (AVNRT) from atrioventricular reciprocating tachycardia (AVRT) when using the RV basal septal stimulation (ΔSA-VAbase) as compared to the RV apical stimulation (ΔSA-VAapex). Moreover, it was predicted that the ΔSA-VAbase might distinguish septal from free wall accessory pathways (APs) effectively. METHODS: In this prospective study, 105 patients with AVNRTs (age 48 ± 20 years, 44% male) and 130 with AVRTs (age 26 ± 18 years, 54% male) underwent programmed ventricular extrastimuli delivered from both the RV basal septum and RV apex. The ΔSA-VA values were compared between the 2 sites. RESULTS: The ΔSA-VAbase was shorter than the ΔSA-VAapex during AVRT (44 ± 30 ms vs 58 ± 29 ms; P < 0.001), and the opposite occurred during AVNRT (133 ± 31 ms vs 125 ± 25 ms; P = 0.03). A ΔSA-VAbase of ≧85 milliseconds had a sensitivity of 97% and specificity of 96% for identifying AVNRT. Furthermore, a ΔSA-VAbase of 45-85 milliseconds identified AVRT with left free wall APs (sensitivity 86%, specificity 95%), 20-45 milliseconds for posterior septal APs (sensitivity 72%, specificity 96%), and <20 milliseconds for right free wall or anterior/mid septal APs (sensitivity 86%, specificity 98%). CONCLUSIONS: The ΔSA-VAbase during programmed ventricular extrastimuli produced a robust differentiation between AVNRT and AVRT regardless of the AP location with ≧85 milliseconds as an excellent cutoff point. This straightforward technique further allowed localizing 4 general AP sites.

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.

Successful Reduction of Postoperative Chest Tube Duration and Length of Stay After Congenital Heart Surgery: A Multicenter Collaborative Improvement Project.

Background Congenital heart disease practices and outcomes vary significantly across centers, including postoperative chest tube (CT) management, which may impact postoperative length of stay (LOS). We used collaborative learning methods to determine whether centers could adapt and safely implement best practices for CT management, resulting in reduced postoperative CT duration and LOS. Methods and Results Nine pediatric heart centers partnered together through 2 learning networks. Patients undergoing 1 of 9 benchmark congenital heart operations were included. Baseline data were collected from June 2017 to June 2018, and intervention-phase data were collected from July 2018 to December 2019. Collaborative learning methods included review of best practices from a model center, regular data feedback, and quality improvement coaching. Center teams adapted CT removal practices (eg, timing, volume criteria) from the model center to their local resources, practices, and setting. Postoperative CT duration in hours and LOS in days were analyzed using statistical process control methodology. Overall, 2309 patients were included. Patient characteristics did not differ between the study and intervention phases. Statistical process control analysis showed an aggregate 15.6% decrease in geometric mean CT duration (72.6 hours at baseline to 61.3 hours during intervention) and a 9.8% reduction in geometric mean LOS (9.2 days at baseline to 8.3 days during intervention). Adverse events did not increase when comparing the baseline and intervention phases: CT replacement (1.8% versus 2.0%, P=0.56) and readmission for pleural effusion (0.4% versus 0.5%, P=0.29). Conclusions We successfully lowered postoperative CT duration and observed an associated reduction in LOS across 9 centers using collaborative learning methodology.

High Acuity Therapy Variation Across Pediatric Acute Care Cardiology Units: Results from the Pediatric Acute Care Cardiology Collaborative Hospital Surveys.

We utilized the multicenter Pediatric Acute Care Cardiology Collaborative (PAC3) 2017 and 2019 surveys to describe practice variation in therapy availability and changes over a 2-year period. A high acuity therapies (ATs) score was derived (1 point per positive response) from 44 survey questions and scores were compared to center surgical volume. Of 31 centers that completed the 2017 survey, 26 also completed the 2019 survey. Scores ranged from 11 to 34 in 2017 and 11 to 35 in 2019. AT scores in 2019 were not statistically different from 2017 scores (29/44, IQR 27-32.5 vs. 29.5/44, IQR 27-31, p = 0.9). In 2019, more centers reported initiation of continuous positive airway pressure (CPAP) and Bi-level positive airway pressure (BiPAP) in Acute Care Cardiology Unit (ACCU) (19/26 vs. 4/26, p < 0.001) and permitting continuous CPAP/BiPAP (22/26 vs. 14/26, p = 0.034) compared to 2017. Scores in both survey years were significantly higher in the highest surgical volume group compared to the lowest, 33 ± 1.5 versus 25 ± 8.5, p = 0.046 and 32 ± 1.7 versus 23 ± 5.5, p = 0.009, respectively. Variation in therapy within the ACCUs participating in PAC3 presents an opportunity for shared learning across the collaborative. Experience with PAC3 was associated with increasing available respiratory therapies from 2017 to 2019. Whether AT scores impact the quality and outcomes of pediatric acute cardiac care will be the subject of further investigation using a comprehensive registry launched in early 2019.

The added value of the advanced practice provider in paediatric acute care cardiology.

OBJECTIVES: Advanced practice providers (APPs) are being employed at increasing rates in order to meet new in-hospital care demands. Utilising the Paediatric Acute Care Cardiology Collaborative (PAC3) hospital survey, we evaluated variations in staffing models regarding first-line providers and assessed associations with programme volume, acuity of care, and post-operative length of stay (LOS). STUDY DESIGN: The PAC3 hospital survey defined staffing models and resource availability across member institutions. A resource acuity score was derived for each participating acute care cardiology unit. Surgical volume was obtained from The Society of Thoracic Surgeons database. Pearson's correlation coefficients were used to evaluate the relationship between staffing models and centre volume as well as unit acuity. A previously developed case-mix adjustment model for total post-operative LOS was utilised in a multinomial regression model to evaluate the association of APP patient coverage with observed-to-expected post-operative LOS. RESULTS: Surveys were completed by 31 (91%) PAC3 centres in 2017. Nearly all centres (94%) employ APPs, with a mean of 1.7 (range 0-5) APPs present on weekday rounds. The number of APPs present has a positive correlation with surgical volume (r = 0.49, p < 0.01) and increased acuity (r = 0.39, p = 0.03). In the multivariate model, as coverage by APPs increased from low to moderate or high, there was greater likelihood of having a shorter-than-expected post-operative LOS (p < 0.001). CONCLUSIONS: The incorporation of paediatric acute care cardiology APPs is associated with reduced post-operative LOS. Future studies are necessary to understand how APPs impact these patient-specific outcomes.

Loss of ventricular preexcitation during noninvasive testing does not exclude high-risk accessory pathways: A multicenter study of WPW in children.

BACKGROUND: Abrupt loss of ventricular preexcitation on noninvasive evaluation, or nonpersistent preexcitation, in Wolff-Parkinson-White syndrome (WPW) is thought to indicate a low risk of life-threatening events. OBJECTIVE: The purpose of this study was to compare accessory pathway (AP) characteristics and occurrences of sudden cardiac arrest (SCA) and rapidly conducted preexcited atrial fibrillation (RC-AF) in patients with nonpersistent and persistent preexcitation. METHODS: Patients 21 years or younger with WPW and invasive electrophysiology study (EPS) data, SCA, or RC-AF were identified from multicenter databases. Nonpersistent preexcitation was defined as absence/sudden loss of preexcitation on electrocardiogram, Holter monitoring, or exercise stress test. RC-AF was defined as clinical preexcited atrial fibrillation with shortest preexcited R-R interval (SPERRI) ≤ 250 ms. AP effective refractory period (APERP), SPERRI at EPS , and shortest preexcited paced cycle length (SPPCL) were collected. High-risk APs were defined as APERP, SPERRI, or SPPCL ≤ 250 ms. RESULTS: Of 1589 patients, 244 (15%) had nonpersistent preexcitation and 1345 (85%) had persistent preexcitation. There were no differences in sex (58% vs 60% male; P=.49) or age (13.3±3.6 years vs 13.1±3.9 years; P=.43) between groups. Although APERP (344±76 ms vs 312±61 ms; P<.001) and SPPCL (394±123 ms vs 317±82 ms; P<.001) were longer in nonpersistent vs persistent preexcitation, there was no difference in SPERRI at EPS (331±71 ms vs 316±73 ms; P=.15). Nonpersistent preexcitation was associated with fewer high-risk APs (13% vs 23%; P<.001) than persistent preexcitation. Of 61 patients with SCA or RC-AF, 6 (10%) had nonpersistent preexcitation (3 SCA, 3 RC-AF). CONCLUSION: Nonpersistent preexcitation was associated with fewer high-risk APs, though it did not exclude the risk of SCA or RC-AF in children with WPW.

Intensive Care Unit and Acute Care Unit Length of Stay After Congenital Heart Surgery.

BACKGROUND: Postoperative length of stay (LOS) is an important quality metric and is known to vary widely across hospitals after congenital heart surgery. Whether this variability is explained by factors associated with the intensive care unit (ICU) or acute care unit (ACU) remains unclear. We evaluated the relationship between ICU and ACU LOS and the impact of ACU characteristics on postoperative LOS. METHODS: Hospitalizations for congenital heart surgery within the Pediatric Cardiac Critical Care Consortium (PC4) registry (August 2014 to February 2018) were included. Models were developed for ICU, ACU, and postoperative LOS by adjusting for differences in case-mix across hospitals. PC4 hospitals participating in the Pediatric Acute Care Cardiology Collaborative (PAC3) were also surveyed on ACU organizational factors and practice patterns. RESULTS: Overall, 19,674 hospitalizations across 27 hospitals were included. There was significant variation in ICU and ACU LOS. Postperative LOS appeared to be most closely related to ICU LOS; 75% (6 of 8) of hospitals with shorter than expected postoperative LOS also had shorter than expected ICU LOS. A clear relationship between postoperative and ACU LOS was not observed. Hospitals with an ACU able to provide higher-acuity care as indexed according to the PAC3 survey were more likely to have shorter postoperative LOS (P < .01). CONCLUSIONS: For hospitals that achieve shorter than expected postoperative LOS after congenital heart surgery, ICU LOS appears to be the primary driver. Higher-acuity resources in the ACU may be an important factor facilitating earlier transfer from the ICU. These data are key to informing quality improvement initiatives geared toward reducing postoperative LOS.

The many faces of early repolarization syndrome: A single-center case series.

BACKGROUND: Early repolarization syndrome (ERS) is a rare but increasingly recognized cause of malignant ventricular arrhythmias. OBJECTIVE: The purpose of this study was to characterize the presentations and treatments of ERS at our institution. METHODS: We performed a retrospective chart review of all patients presenting to our institution between 2008 and 2019 with ERS. Exclusion criteria included Brugada syndrome, positive provocative testing with class I antiarrhythmic drugs, metabolic disturbances, or structural heart disease. RESULTS: Of 10 patients identified with ERS, 8 were men with a mean age of 30 ± 17 years at diagnosis. Documented arrhythmias included ventricular fibrillation in 7 of 10, polymorphic ventricular tachycardia in 3 of 10, and monomorphic ventricular tachycardia in 3 of 10 patients. Atrial fibrillation was diagnosed in 3 of 10, and atrioventricular block was seen in 2 of 10. J waves and/or electrocardiographic early repolarization patterns were dynamic in 7 of 10. Arrhythmias occurred at rest in 8 of 10 and with exertion in 2 of 10. Only 1 patient had a family history of sudden death, and 4 of 10 patients had variants of uncertain significance on genetic testing. Quinidine effectively suppressed arrhythmias in 5 of 5 patients but required dose escalation to >1 g/d in 3 of 5 patients. Abnormal epicardial electrograms were recorded over the inferolateral left ventricle in 2 patients who underwent mapping and were successfully ablated. Premature ventricular contraction triggers were also targeted for ablation in 3 patients. CONCLUSION: ERS is a heterogeneous condition and may be associated with both atrial and ventricular arrhythmias, atrioventricular block, dynamic electrocardiographic changes, and variable triggers. In addition to targeting premature ventricular contraction triggers, mapping and ablation of abnormal epicardial electrograms may be a potential future treatment strategy.

Center Variation in Chest Tube Duration and Length of Stay After Congenital Heart Surgery.

BACKGROUND: Nearly every child undergoing congenital heart surgery has chest tubes placed intraoperatively. Center variation in removal practices and impact on outcomes has not been well described. This study evaluated variation in chest tube management practices and outcomes across centers. METHODS: The study included patients undergoing any of 10 benchmark operations from June 2017 to May 2018 at participating Pediatric Acute Care Cardiology Collaborative (PAC3) and Pediatric Cardiac Critical Care Consortium (PC4) centers. Clinical data from PC4 centers were merged with chest tube data from PAC3 centers. Practices and outcomes were compared across centers in univariate and multivariable analysis. RESULTS: The cohort included 1029 patients (N = 9 centers). Median chest tube duration varied significantly across centers for 9 of 10 benchmark operations (all P ≤ .03), with a "model" center noted to have the shortest duration for 9 of 10 operations (range, 27.9% to 87.4% shorter duration vs other centers across operations). This effect persisted in multivariable analysis (P < .0001). The model center had higher volumes of chest tube output before removal (median, 8.5 mL/kg/24 h [model] vs 2.2 mL/kg/24 h [other centers]; P < .001], but it did not have higher rates of chest tube reinsertion (model center 1.3% vs 2.1%; P = .59) or readmission for pleural effusion (model center 4.4% vs 3.0%; P = .31), and had the shortest length of stay for 7 of 10 operations. CONCLUSIONS: This study suggests significant center variation in chest tube removal practices and associated outcomes after congenital heart surgery. Best practices used at the model center have informed the design of an ongoing collaborative learning project aimed at reducing chest tube duration and length of stay.

Variable Presentations and Ablation Sites for Manifest Nodoventricular/Nodofascicular Fibers.

BACKGROUND: Nodofascicular and nodoventricular (NFV) accessory pathways connect the atrioventricular node and the Purkinje system or ventricular myocardium, respectively. Concealed NFV pathways participate as the retrograde limb of supraventricular tachycardia (SVT). Manifest NFV pathways can comprise the anterograde limb of wide-complex SVT but are quite rare. The purpose of this report is to highlight the electrophysiological properties and sites of ablation for manifest NFV pathways. METHODS: Eight patients underwent electrophysiology studies for wide-complex tachycardia (3), for narrow-complex tachycardia (1), and preexcitation (4). RESULTS: NFV was an integral part of the SVT circuit in 3 patients. Cases 1 to 2 were wide-complex tachycardia because of manifest NFV SVT. Case 3 was a bidirectional NFV that conducted retrograde during concealed NFV SVT and anterograde causing preexcitation during atrial pacing. NFV was a bystander during atrioventricular node re-entrant tachycardia, atrial fibrillation, atrial flutter, and orthodromic atrioventricular re-entrant tachycardia in 4 cases and caused only preexcitation in 1. Successful NFV ablation was achieved empirically in the slow pathway region in 1 case. In 5 cases, the ventricular insertion was mapped to the slow pathway region (2 cases) or septal right ventricle (3 cases). The NFV was not mapped in cases 5 and 7 because of its bystander role. QRS morphology of preexcitation predicted the right ventricle insertion sites in 4 of the 5 cases in which it was mapped. During follow-up, 1 patient noted recurrent palpitations but no documented SVT. CONCLUSIONS: Manifest NFV may be critical for wide-complex tachycardia/manifest NFV SVT, act as the retrograde limb for narrow-complex tachycardia/concealed NFV SVT, or cause bystander preexcitation. Ablation should initially target the slow pathway region, with mapping of the right ventricle insertion site if slow pathway ablation is not successful. The QRS morphology of maximal preexcitation may be helpful in predicting successful right ventricle ablation site.

Comparison of Electrophysiologic Profiles in Pediatric Patients with Incidentally Identified Pre-Excitation Compared with Wolff-Parkinson-White Syndrome.

The rising utilization of screening electrocardiograms has resulted in increased incidental identification of ventricular pre-excitation in pediatric patients. We compared accessory pathways of incidentally identified pre-excitation to Wolff-Parkinson-White Syndrome (WPW) with the aim to identify factors important in preprocedural counseling and planning. This single-center, retrospective study of patients ≤18 years without congenital heart disease identified 227 patients diagnosed with pre-excitation and referred for invasive electrophysiology study between 2008 and 2017. WPW Syndrome was diagnosed in 178 patients, while 49 patients had incidental identification of pre-excitation. Anterograde conduction of incidentally identified accessory pathways was not clinically different between the two cohorts at baseline or upon isoproterenol infusion. However, the proportion of accessory pathways meeting high-risk criteria was significantly lower than in patients diagnosed with WPW, 12% versus 28% (p < 0.05). Retrograde conduction at baseline of incidentally diagnosed accessory pathways was slower with a median block cycle length 365 milliseconds (IQR 260 to 450) versus 290 milliseconds (IQR 260 to 330, p < 0.01). In the incidentally identified cohort, right-sided, paraHisian, and fascicular pathways were more common with fewer attempted ablations (71% vs 94%, p < 0.001) and lower success rate (91% vs 97%, p < 0.001). A binomial logistic regression analysis further indicated patients incidentally identified with pre-excitation were associated with having lower rates of inducible supraventricular tachycardia, atrial fibrillation, and ablations performed, in addition, to having right-sided pathways. In conclusion, as patients with incidentally identified pre-excitation present more frequently for consideration of invasive electrophysiology study, these results impact procedural approaches, technical considerations, patient counseling, and outcome expectations.

Atrioventricular block after congenital heart surgery: Analysis from the Pediatric Cardiac Critical Care Consortium.

OBJECTIVES: Our primary aims were to describe the contemporary epidemiology of postoperative high-grade atrioventricular block (AVB), the timing of recovery and permanent pacemaker (PPM) placement, and to determine predictors for development of and recovery from AVB. METHODS: Patients who underwent congenital heart surgery from August 2014 to June 2017 were analyzed for AVB using the Pediatric Cardiac Critical Care Consortium registry. Predictors of AVB with or without PPM were identified using multinomial logistic regression. We used these predictors to model the probability of PPM for the subgroup of patients with intraoperative complete AVB. RESULTS: We analyzed 15,901 surgical hospitalizations; 422 (2.7%) were complicated by AVB and 162 (1.0%) patients underwent PPM placement. In patients with transient AVB, 50% resolved by 2 days, and 94% resolved by 10 days. In patients who received a PPM, 50% were placed by 8 days and 62% were placed by 10 days. Independent risk factors associated with PPM compared with resolution of AVB were longer duration of cardiopulmonary bypass (relative risk ratio, 1.04; P = .023) and a high-risk operation (relative risk ratio, 2.59; P < .001). Among patients with complete AVB originating in the operating room, those with the highest predicted probability of PPM had a PPM placed only 77% of the time. CONCLUSIONS: In this cohort, postoperative AVB complicated almost 3% of congenital heart surgery cases and 1% of patients underwent PPM placement. Because almost all patients (94%) with transient AVB had resolution by 10 days, our results suggest there is limited benefit to delaying PPM placement beyond that time frame.

Variation in care practices across pediatric acute care cardiology units: Results of the Pediatric Acute Care Cardiology Collaborative (PAC3 ) hospital survey.

BACKGROUND: The Pediatric Acute Care Cardiology Collaborative (PAC3 ) was established in 2014 to improve the quality, value, and experience of hospital-based cardiac acute care outside of the intensive care unit. An initial PAC3 project was a comprehensive survey to understand unit structure, practices, and resource utilization across the collaborative. This report aims to describe the previously unknown degree of practice variation across member institutions. METHODS: A 126-stem question survey was developed with a total of 412 possible response fields across nine domains including demographics, staffing, available resources and therapies, and standard care practices. Five supplemental questions addressed surgical case volume and number of cardiac acute care unit (CACU) admissions. Responses were recorded and stored in Research Electronic Data Capture (REDCap). RESULTS: Surveys were completed by 31 out of 34 centers (91%) with minimal incomplete fields. A majority (61%) of centers have a single dedicated CACU, which is contiguous or adjacent to the intensive care unit in 48%. A nurse staffing ratio of 3:1 is most common (71%) and most (84%) centers employed a resource nurse. Centralized wireless rhythm monitoring is used in 84% of centers with 54% staffed continuously. There was significant variation in the use of noninvasive respiratory support, vasoactive infusions, and ventricular assist devices across the collaborative. Approximately half of the surveyed centers had lesion-specific postoperative pathways and approximately two-thirds had protocols for single-ventricle patients. CONCLUSIONS: The PAC3 hospital survey is the most comprehensive description of systems and care practices unique to CACUs to date. There exists considerable heterogeneity among unit composition and variation in care practices. These variations may allow for identification of best practices and improved quality of care for patients.

What have we learned in the last 20 years? A comparison of a modern era pediatric and congenital catheter ablation registry to previous pediatric ablation registries.

BACKGROUND: Since the onset of pediatric catheter ablation, the pediatric electrophysiology community has reported outcomes via various registries (PAPCA [Prospective Assessment After Pediatric Cardiac Ablation], PCAR [Pediatric Catheter Ablation Registry]). Most recently, a modern era pediatric and congenital ablation registry (MAP-IT [Multicenter Pediatric and Congenital EP Quality Initiative]) was developed for eventual incorporation into the National Cardiovascular Data Registry (NCDR) IMPACT (Improving Pediatric and Adult Congenital Treatment) registry. OBJECTIVE: The purpose of this study was to describe initial findings from the MAP-IT pilot registry and to compare these findings to earlier registries. METHODS: Before entering the NCDR IMPACT registry, MAP-IT was active at 12 centers (11 in the United States) between October 2014 and April 2016. All electrophysiological studies for patients younger than 21 years and for patients of all ages with structural congenital heart disease were included. We compared the acute success, fluoroscopy and procedural times, and frequency of complications between MAP-IT and the earlier registries. RESULTS: Acute success rates have improved from the initial PCAR registry for both accessory and slow pathway substrates. Both fluoroscopy and procedural times have significantly decreased across the time periods (fluoroscopy time 47.6 ± 40 minutes to 7.0 ± 9.2 minutes; P <.001; procedural time 257 ± 157 minutes to 166 ± 84 minutes; P <.001). CONCLUSION: Acute success rates and fluoroscopy and procedural times in pediatric ablation all have improved over the last 25 years.

Life-Threatening Event Risk in Children With Wolff-Parkinson-White Syndrome: A Multicenter International Study.

OBJECTIVES: This study sought to characterize risk in children with Wolff-Parkinson-White (WPW) syndrome by comparing those who had experienced a life-threatening event (LTE) with a control population. BACKGROUND: Children with WPW syndrome are at risk of sudden death. METHODS: This retrospective multicenter pediatric study identified 912 subjects ≤21 years of age with WPW syndrome, using electrophysiology (EPS) studies. Case subjects had a history of LTE: sudden death, aborted sudden death, or atrial fibrillation (shortest pre-excited RR interval in atrial fibrillation [SPERRI] of ≤250 ms or with hemodynamic compromise); whereas subjects did not. We compared clinical and EPS data between cases and subjects. RESULTS: Case subjects (n = 96) were older and less likely than subjects (n = 816) to have symptoms or documented tachycardia. Mean age at LTE was 14.1 ± 3.9 years of age. The LTE was the sentinel symptom in 65%, consisting of rapidly conducted pre-excited atrial fibrillation (49%), aborted sudden death (45%), and sudden death (6%). Three risk components were considered at EPS: SPERRI, accessory pathway effective refractory period (APERP), and shortest paced cycle length with pre-excitation during atrial pacing (SPPCL), and all were shorter in cases than in control subjects. In multivariate analysis, risk factors for LTE included male sex, Ebstein malformation, rapid anterograde conduction (APERP, SPERRI, or SPPCL ≤250 ms), multiple pathways, and inducible atrial fibrillation. Of case subjects, 60 of 86 (69%) had ≥2 EPS risk stratification components performed; 22 of 60 (37%) did not have EPS-determined high-risk characteristics, and 15 of 60 (25%) had neither concerning pathway characteristics nor inducible atrioventricular reciprocating tachycardia. CONCLUSIONS: Young patients may experience LTE from WPW syndrome without prior symptoms or markers of high-risk on EPS.

Use of Programmed Ventricular Extrastimulus During Supraventricular Tachycardia to Differentiate Atrioventricular Nodal Re-Entrant Tachycardia From Atrioventricular Re-Entrant Tachycardia.

OBJECTIVES: This study hypothesized that early coupled ventricular extrastimuli (V2) stimulation might yield a more robust differentiation between atrioventricular nodal re-entrant tachycardia (AVNRT) and atrioventricular re-entrant tachycardia (AVRT). BACKGROUND: Programmed V2 during supraventricular tachycardia are useful to differentiate AVNRT from AVRT by subtracting the ventriculoatrial (VA) interval from the stimulus to atrial depolarization (stimulus atrial [SA]) interval, but all such maneuvers have limitations. METHODS: Patients with either AVNRT or AVRT were investigated. The entire tachycardia cycle length (TCL) was scanned with V2 delivered from the right ventricular apex. The SA-VA difference was calculated with V2 clearly resetting the tachycardia. The prematurity of V2 was calculated by dividing the coupling interval (CI) by the TCL. RESULTS: A total of 210 patients (102 with AVNRT) were included. The SA-VA difference was >70 ms in all AVNRT patients and was <70 ms in all AVRT patients with right and septal accessory pathways (APs), except for those with decremental APs, in whom there was an overlap between AVNRT and AVRT with left APs. However, a SA-VA difference >110 ms with a CI/TCL of <65% distinguished AVNRT from AVRT using the left AP, with sensitivity and specificity of 87% and 100%, respectively. Ventricular overdrive pacing resulted in tachycardia termination or AV dissociation in 28% of patients compared with 15% of patients using the V2 technique (p = 0.008). CONCLUSIONS: A SA-VA of >70 ms using the V2 technique differentiated AVNRT from AVRT using septal and right APs. Use of the V2 technique with a short CI differentiated AVNRT from AVRT using left APs. The V2 technique less frequently resulted in tachycardia termination compared with ventricular entrainment.

Perioperative Factors Influence the Long-Term Outcomes of Children and Adolescents with Repaired Tetralogy of Fallot.

Tetralogy of Fallot (TOF) often carries long-term seqüelae following surgical intervention. We hypothesized that early perioperative factors are associated with long-term adverse right ventricular (RV) remodeling, diminished exercise capacity, and increased morbidity. We conducted a retrospective cohort study of patients operated for TOF that underwent cardiac magnetic resonance imaging study (CMR), exercise stress test (EST), and detailed review of past medical history. Outcome variables included measures of RV size, and function, maximal work rate, and oxygen consumption, and interim hospitalizations, surgeries, and catheterizations. Thirty-nine subjects were included. Age at surgical repair was 0.3 ± 0.3 years and age at testing was 9.7 ± 1.4 years. On CMR, there was borderline RV dilation with moderate pulmonary insufficiency (PI) [RF 32% (8; 43)] and normal RV ejection fraction [60% (55; 67)]. On EST, there was low percent-predicted maximal oxygen consumption (77 ± 20%), and percent-predicted maximal work rate (84 ± 23%). On multivariable analysis, mechanical ventilation and Blalock-Taussig (BT) shunt prior to complete surgical repair were associated with the number of future hospitalizations. Duration of cardiopulmonary bypass and prior BT shunt were associated with future catheterizations. Prior BT shunt was a predictor of worse RVEF, while duration of mechanical ventilation and use of transannular patch were predictors of worse PI. Longer duration of mechanical ventilation (or LOS) was associated with worse maximal work rate. Surgical and perioperative factors may portend long-term RV remodeling and outcome in TOF. Further studies are warranted to explore these associations and potential underlying mechanisms.

Collective quality improvement in the paediatric cardiology acute care unit: establishment of the Pediatric Acute Care Cardiology Collaborative (PAC3).

Collaborative quality improvement and learning networks have amended healthcare quality and value across specialities. Motivated by these successes, the Pediatric Acute Care Cardiology Collaborative (PAC3) was founded in late 2014 with an emphasis on improving outcomes of paediatric cardiology patients within cardiac acute care units; acute care encompasses all hospital-based inpatient non-intensive care. PAC3 aims to deliver higher quality and greater value care by facilitating the sharing of ideas and building alignment among its member institutions. These aims are intentionally aligned with the work of other national clinical collaborations, registries, and parent advocacy organisations. The mission and early work of PAC3 is exemplified by the formal partnership with the Pediatric Cardiac Critical Care Consortium (PC4), as well as the creation of a clinical registry, which links with the PC4 registry to track practices and outcomes across the entire inpatient encounter from admission to discharge. Capturing the full inpatient experience allows detection of outcome differences related to variation in care delivered outside the cardiac ICU and development of benchmarks for cardiac acute care. We aspire to improve patient outcomes such as morbidity, hospital length of stay, and re-admission rates, while working to advance patient and family satisfaction. We will use quality improvement methodologies consistent with the Model for Improvement to achieve these aims. Membership currently includes 36 centres across North America, out of which 26 are also members of PC4. In this report, we describe the development of PAC3, including the philosophical, organisational, and infrastructural elements that will enable a paediatric acute care cardiology learning network.

22q11.2 Deletion Status and Perioperative Outcomes for Tetralogy of Fallot with Pulmonary Atresia and Multiple Aortopulmonary Collateral Vessels.

Deletion of 22q11.2 (del22q11) is associated with adverse outcomes in patients with tetralogy of Fallot (TOF). We sought to investigate its contribution to perioperative outcome in patients with a severe form of TOF characterized by pulmonary atresia (PA) or severe pulmonary stenosis (PS) and major aortopulmonary collateral arteries (MAPCAS). We conducted a retrospective review of patients with TOF/MAPCAS who underwent staged surgical reconstruction between 1995 and 2006. Groups were compared according to 22q11.2 deletion status using t-tests or the Wilcoxon Rank sum test. We included 26 subjects, 24 of whom survived the initial operation. Of those, 21 subjects had known deletion status and constitute the group for this analysis [15 with no deletion present (ND) and 6 del22q11 subjects]. There was no difference with respect to occurrence of palliative procedure prior to initial operation, or to timing of closure of the ventricular septal defect (VSD). Other than higher prevalence of prematurity (50%) in the del22q11 group versus no prematurity in the ND, the groups were comparable in terms of pre-operative characteristics. The intra- and post-operative course outcomes (length of cardiopulmonary bypass, use of vasopressors, duration of intensive care and length of hospital stay, tube-feeding) were also comparable. Although the del22q11 had longer mechanical ventilation than the ND, this difference was not significant [68 h (range 4-251) vs. 45 h (range 3-1005), p = 0.81]. In this detailed comparison of a small patient cohort, 22q11.2 deletion syndrome was not associated with adverse perioperative outcomes in patients with TOF, PA, and MAPCAS when compared to those without 22q11.2 deletion syndrome. These results are relevant to prenatal and neonatal pre-operative counseling and planning.