In Vivo Molding of Airway Stents.

Like ready-to-wear clothing, medical devices come in a fixed set of sizes. While this may accommodate a large fraction of the patient population, others must either experience suboptimal results due to poor sizing or must do without the device. Although techniques have been proposed to fabricate patient-specific devices in advance of a procedure, this process is expensive and time consuming. An alternative solution that provides every patient with a tailored fit is to create devices that can be customized to the patient's anatomy as they are delivered. This paper reports an in vivo molding process in which a soft flexible photocurable stent is delivered into the trachea or bronchi over a UV-transparent balloon. The balloon is expanded such that the stent conforms to the varying cross-sectional shape of the airways. UV light is then delivered through the balloon curing the stent into its expanded conformal shape. The potential of this method is demonstrated using phantom, ex vivo and in vivo experiments. This approach can produce stents providing equivalent airway support to those made from standard materials while providing a customized fit.

Hyperlactataemia as a predictor of adverse outcomes post-cardiac surgery in neonates with congenital heart disease.

OBJECTIVE: To evaluate the discriminative ability of hyperlactataemia for early morbidity and mortality in neonates with CHD following cardiac surgery. METHODS: Retrospective, observational study of neonates who underwent cardiac surgery on cardiopulmonary bypass at a tertiary care children's hospital from June 2015 to June 2019. The primary predictor was lactate. The primary composite outcome was defined as ≥1 of the following: cardiac arrest or extracorporeal membrane oxygenation within 72 hours or 30-day mortality post-operatively. The secondary outcome was the presence of major residual lesions, according to the Technical Performance Score. RESULTS: Of 432 neonates, 28 (6.5%) sustained the composite outcome. On univariate analysis, peak lactate within 48 hours, increase in lactate from ICU admission through 12 hours, and single ventricle physiology were significantly associated with the composite outcome. The peak lactate occurred at a median of 2.9 hours (interquartile range: 1, 35) before the event. Through multi-variable analysis, a multi-variable risk algorithm was created. Predicted probabilities demonstrated an increasing risk based on single ventricle status and delta lactate, ranging from 1.8% (95% CI: 0.9, 3.9) to 52.4% (95% CI: 32.4, 71.7). The model had good discriminative ability for the composite outcome on receiver operating characteristic analysis (area under the curve = 0.79; 95% CI: 0.75, 0.89). Moreover, a peak lactate of 7.3 mmol/l or greater was significantly associated with the presence of a major residual lesion (odds ratios: 5.16, 95% CI: 3.01, 8.87). CONCLUSIONS: We present a simple, two-variable model, including delta lactate in the immediate post-operative period and single ventricle status, to prognosticate the risk of early morbidity and mortality in neonates undergoing cardiac surgery for potential intervention.

Left Ventricular Outflow Tract Obstruction: Coarctation of the Aorta, Interrupted Aortic Arch, and Borderline Left Ventricle.

OBJECTIVES: The objectives of this review are to discuss the perioperative management of coarctation of the aorta, interrupted aortic arch, and the borderline left ventricle. METHODS: MEDLINE and PubMed. CONCLUSIONS: Successful management of systemic obstructive lesions involves a thorough evaluation of the anatomy and pathophysiology to determine the most effective management strategy.

Association of Extracorporeal Membrane Oxygenation Support Adequacy and Residual Lesions With Outcomes in Neonates Supported After Cardiac Surgery.

OBJECTIVES: There is a paucity of data regarding the impact of extracorporeal membrane oxygenation support, adequacy of surgical repair, and timing of intervention for residual structural lesions in neonates cannulated to extracorporeal membrane oxygenation after cardiac surgery. Our goal was to determine how these factors were associated with survival. DESIGN: Retrospective study. SETTING: Cardiovascular ICU. SUBJECTS: Neonates (≤ 28 d old) with congenital heart disease cannulated to extracorporeal membrane oxygenation after cardiac surgery during 2006-2013. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Eighty-four neonates were cannulated to venoarterial extracorporeal membrane oxygenation after cardiac surgery. Survival to discharge was 50%. There was no difference in survival based on surgical complexity and those with single or biventricular congenital heart disease. Prematurity (≤ 36 wk gestation; odds ratio, 2.33; p = 0.01), preextracorporeal membrane oxygenation pH less than or equal to 7.17 (odds ratio, 2.01; p = 0.04), need for inotrope support during extracorporeal membrane oxygenation (odds ratio, 3.99; p = 0.03), and extracorporeal membrane oxygenation duration greater than 168 hours (odds ratio, 2.04; p = 0.04) were all associated with increased mortality. Although preextracorporeal membrane oxygenation lactate was not significantly different between survivors and nonsurvivors, unresolved lactic acidosis greater than or equal to 72 hours after cannulation (odds ratio, 2.77; p = 0.002) was associated with increased mortality. Finally, many patients (n = 70; 83%) were noted to have residual lesions after cardiac surgery, and time to diagnosis or correction of residual lesions was significantly shorter in survivors (1 vs 2 d; p = 0.02). CONCLUSIONS: Our data suggest that clearance of lactate is an important therapeutic target for patients cannulated to extracorporeal membrane oxygenation. In addition, timely identification of residual lesions and expedient interventions on those lesions may improve survival.

Are Bioprosthetic Valves Appropriate for Aortic Valve Replacement in Young Patients?

Selection of a prosthetic aortic valve for use in the young patient is complicated by a variety of important considerations. Age, growth potential, activity and life style expectations, child bearing, and social factors, in addition to anatomic considerations, are all important to the recommendation of a prosthetic valve choice. We review the clinical experience and expectations of currently available prosthetic aortic valves available for the young patient, and describe the advantages and disadvantages for each.

Association of tetralogy of Fallot and complete atrioventricular canal: a single-centre 40-year experience.

OBJECTIVES: Outcome data in tetralogy of Fallot (ToF) and complete atrioventricular canal (CAVC) are limited. We report our experience for over 40 years in this patient population. METHODS: Single-centre, retrospective analysis of patients who underwent surgical repair with the diagnosis of ToF-CAVC from 1979 to 2022, divided into 2 different periods and compared. RESULTS: A total of 116 patients were included: 1979-2007 (n = 61) and 2008-2021 (n = 55). Balanced CAVC (80%) and Rastelli type C CAVC (81%) were most common. Patients in the later era were younger (4 vs 14 months, P < 0.001), fewer had trisomy 21 (60% vs 80%, P = 0.019) and fewer had prior palliative prior procedures (31% vs 43%, P < 0.001). In the earlier era, single-patch technique was more common (62% vs 16%, P < 0.001), and in recent era, double-patch technique was more common (84% vs 33%, P < 0.001). In the earlier era, right ventricular outflow tract was most commonly reconstructed with transannular patch (51%), while in more recent era, valve-sparing repairs were more common (69%) (P < 0.001). In-hospital mortality was 4.3%. The median follow-up was 217 and 74 months for the first and second eras. Survival for earlier and later eras at 2-, 5- and 10-year follow-up was (85.1%, 81.5%, 79.6% vs 94.2%, 94.2%, 94.2% respectively, log-rank test P = 0.03). CONCLUSIONS: The surgical approach to ToF-CAVC has evolved over time. More recently, patients tended to receive primary repair at younger ages and had fewer palliative procedures. Improved surgical techniques allowing for earlier and complete repair have shown a decrease in mortality, more valve-sparing procedures without an increase in total reoperations. Presented at the 37th EACTS Annual Meeting, Vienna, Austria.

Surgical approaches for CHD: and update on success and challenges.

PURPOSE OF REVIEW: Congenital heart surgery is a constantly evolving specialty informed by experience and science. Recent trends confirm this with three key findings that challenge existing dogma and suggest new paths. These include: surgical aortic valve intervention vs. balloon valvotomy, shunt type in staged palliation for hypoplastic left heart syndrome (HLHS), and strategies for selective cerebral perfusion (SCP). RECENT FINDINGS: Early surgical aortic valve intervention vs. traditional balloon aortic valvuloplasty; shunt type in staged palliation for hypoplastic left heart syndrome; strategies for SCP. SUMMARY: We reviewed the current literature for congenital heart disease in the last year. We identified a number of surgical themes that suggest a move of the field in new directions. First is a re-examination of strategies for early intervention in critical aortic stenosis. Although balloon valvotomy has been the standard therapy for this disease over the last 20 years, data now suggest a potential role for primary surgery in this disease. Secondly, we examine new results for palliation of HLHS. The Pediatric Heart Network's (PHN) single ventricle reconstruction (SVR) trial compared shunt types. However, palliation for HLHS is a three-stage process and final judgment regarding the best strategy for stage I palliation should be reserved for an analysis of post-Fontan palliation. New data from the PHN are now beginning to show equipoise for the two palliative strategies. Third, we examine new studies that exemplify the complexities that underlie SCP strategies as an alternative to deep hypothermic circulatory arrest (DHCA). In all cases, sequential movement forward suggests that either continued or more rigorous prospective randomized studies be performed to unravel the complexities of treatment for congenital heart disease.

Cardiac performance and quality of life in patients who have undergone the Fontan procedure with and without prior superior cavopulmonary connection.

BACKGROUND: A superior cavopulmonary connection is commonly performed before the Fontan procedure in patients with a functionally univentricular heart. Data are limited regarding associations between a prior superior cavopulmonary connection and functional and ventricular performance late after the Fontan procedure. METHODS: We compared characteristics of those with and without prior superior cavopulmonary connection among 546 subjects enrolled in the Pediatric Heart Network Fontan Cross-Sectional Study. We further compared different superior cavopulmonary connection techniques: bidirectional cavopulmonary anastomosis (n equals 229), bilateral bidirectional cavopulmonary anastomosis (n equals 39), and hemi-Fontan (n equals 114). RESULTS: A prior superior cavopulmonary connection was performed in 408 subjects (75%); the proportion differed by year of Fontan surgery and centre (p-value less than 0.0001 for each). The average age at Fontan was similar, 3.5 years in those with superior cavopulmonary connection versus 3.2 years in those without (p-value equals 0.4). The type of superior cavopulmonary connection varied by site (p-value less than 0.001) and was related to the type of Fontan procedure. Exercise performance, echocardiographic variables, and predominant rhythm did not differ by superior cavopulmonary connection status or among superior cavopulmonary connection types. Using a test of interaction, findings did not vary according to an underlying diagnosis of hypoplastic left heart syndrome. CONCLUSIONS: After controlling for subject and era factors, most long-term outcomes in subjects with a prior superior cavopulmonary connection did not differ substantially from those without this procedure. The type of superior cavopulmonary connection varied significantly by centre, but late outcomes were similar.

A novel ex vivo tracheobronchomalacia model for airway stent testing and in vivo model refinement.

OBJECTIVES: We sought to develop an ex vivo trachea model capable of producing mild, moderate, and severe tracheobronchomalacia for optimizing airway stent design. We also aimed to determine the amount of cartilage resection required for achieving different tracheobronchomalacia grades that can be used in animal models. METHODS: We developed an ex vivo trachea test system that enabled video-based measurement of internal cross-sectional area as intratracheal pressure was cyclically varied for peak negative pressures of 20 to 80 cm H2O. Fresh ovine tracheas were induced with tracheobronchomalacia by single mid-anterior incision (n = 4), mid-anterior circumferential cartilage resection of 25% (n = 4), and 50% per cartilage ring (n = 4) along an approximately 3-cm length. Intact tracheas (n = 4) were used as control. All experimental tracheas were mounted and experimentally evaluated. In addition, helical stents of 2 different pitches (6 mm and 12 mm) and wire diameters (0.52 mm and 0.6 mm) were tested in tracheas with 25% (n = 3) and 50% (n = 3) circumferentially resected cartilage rings. The percentage collapse in tracheal cross-sectional area was calculated from the recorded video contours for each experiment. RESULTS: Ex vivo tracheas compromised by single incision and 25% and 50% circumferential cartilage resection produce tracheal collapse corresponding to clinical grades of mild, moderate, and severe tracheobronchomalacia, respectively. A single anterior cartilage incision produces saber-sheath type tracheobronchomalacia, whereas 25% and 50% circumferential cartilage resection produce circumferential tracheobronchomalacia. Stent testing enabled the selection of stent design parameters such that airway collapse associated with moderate and severe tracheobronchomalacia could be reduced to conform to, but not exceed, that of intact tracheas (12-mm pitch, 0.6-mm wire diameter). CONCLUSIONS: The ex vivo trachea model is a robust platform that enables systematic study and treatment of different grades and morphologies of airway collapse and tracheobronchomalacia. It is a novel tool for optimization of stent design before advancing to in vivo animal models.

Transcatheter Ductal Stents Versus Surgical Systemic-Pulmonary Artery Shunts in Neonates With Congenital Heart Disease With Ductal-Dependent Pulmonary Blood Flow: Trends and Associated Outcomes From the Pediatric Health Information System Database.

Background Surgical systemic-to-pulmonary artery shunts have been the standard approach to establish stable pulmonary blood flow in neonates with congenital heart disease with ductal-dependent pulmonary blood flow. More recently, transcatheter ductal stents have been performed as an alternative, less invasive intervention. We aimed to characterize trends in the utilization of surgical shunts versus ductal stents and compare associated outcomes. Methods and Results Using data from the Pediatric Health Information System, we retrospectively analyzed neonates with congenital heart disease with ductal-dependent pulmonary blood flow who underwent surgical shunt or ductal stent placement between January 2016 and December 2021. Patients were identified by International Classification of Diseases, Tenth Revision (ICD-10) diagnosis and procedure codes. The primary outcome was length of hospital stay. Secondary outcomes were reintervention risk and adjusted hospital costs. Of 936 patients included, 65.2% underwent a surgical shunt over the 6-year period. The proportion who underwent ductal stenting increased from 19% to 53.4% from 2016 to 2021. The median adjusted difference in postintervention length of hospital stay was 11 days greater for the surgical shunt cohort (95% CI, 7.2-14.8; P<0.001). The adjusted reintervention risks within 3 (odds ratio [OR], 3.37 [95% CI, 1.91-5.95], P<0.001) and 6 months (OR, 2.43 [95% CI, 1.62-3.64], P<0.001) were significantly greater in the ductal stent group. Median adjusted index hospital costs were $198 300 ($11 6400-$340 000) versus $120 400 ($81 800-$192 400) for the surgical shunt and ductal stent cohorts, respectively (P<0.001). Conclusions Ductal stenting has become an increasingly utilized palliative approach to secure pulmonary blood flow in neonates with congenital heart disease with ductal-dependent pulmonary blood flow in the United States. Ductal stenting is associated with decreased length of hospital stay and reduced overall cost for the index hospitalization but with a greater reintervention risk than surgical shunting.

Impact of Neighborhood Socioeconomic Status on Outcomes Following First-Stage Palliation of Single Ventricle Heart Disease.

Background The impact of neighborhood socioeconomic status (SES) on outcomes following first-stage palliation of single ventricle heart disease remains incompletely characterized. Methods and Results This was a single-center, retrospective review of consecutive patients who underwent the Norwood procedure from January 1, 1997 to November 11, 2017. Outcomes of interest included in-hospital (early) mortality or transplant, postoperative hospital length-of-stay, inpatient cost, and postdischarge (late) mortality or transplant. The primary exposure was neighborhood SES, assessed using a composite score derived from 6 US census-block group measures related to wealth, income, education, and occupation. Associations between SES and outcomes were assessed using logistic regression, generalized linear, or Cox proportional hazards models, adjusting for baseline patient-related risk factors. Of 478 patients, there were 62 (13.0%) early deaths or transplants. Among 416 transplant-free survivors at hospital discharge, median postoperative hospital length-of-stay and cost were 24 (interquartile range, 15-43) days and $295 000 (interquartile range, $193 000-$563 000), respectively. There were 97 (23.3%) late deaths or transplants. On multivariable analysis, patients in the lowest SES tertile had greater risk of early mortality or transplant (odds ratio [OR], 4.3 [95% CI, 2.0-9.4; P<0.001]), had longer hospitalizations (coefficient 0.4 [95% CI, 0.2-0.5; P<0.001]), incurred higher costs (coefficient 0.5 [95% CI, 0.3-0.7; P<0.001]), and had greater risk of late mortality or transplant (hazard ratio, 2.2 [95% CI, 1.3-3.7; P=0.004]), compared with those in the highest tertile. The risk of late mortality was partially attenuated with successful completion of home monitoring programs. Conclusions Lower neighborhood SES is associated with worse transplant-free survival following the Norwood operation. This risk persists throughout the first decade of life and may be mitigated with successful completion of interstage surveillance programs.

Cost of Pacing in Pediatric Patients With Postoperative Heart Block After Congenital Heart Surgery.

Importance: Surgical correction of congenital heart defects (CHDs) has improved the lifespan and quality of life of pediatric patients. The number of congenital heart surgeries (CHSs) in children has grown continuously since the 1960s. This growth has been accompanied by a rise in the incidence of postoperative heart block requiring permanent pacemaker (PPM) implantation. Objective: To assess the trends in permanent pacing after CHS and estimate the economic burden to patients and their families after PPM implantation. Design, Setting, and Participants: In this economic evaluation study, procedure- and diagnosis-specific codes within a single-institution database were used to identify patients with postoperative heart block after CHS between January 1, 1960, and December 31, 2018. Patients younger than 4 years with postoperative PPM implantation were selected, and up to 20-year follow-up data were used for cost analysis based on mean hospital event charges and length of stay (LOS) data. Data were analyzed from January 1, 2020, to November 30, 2022. Exposure: Implantation of PPM after CHS in pediatric patients. Main Outcomes and Measures: Annual trends in CHS and postoperative PPM implantations were assessed. Direct and indirect costs associated with managing conduction health for the 20 years after PPM implantation were estimated using Markov model simulation and patient follow-up data. Results: Of the 28 225 patients who underwent CHS, 968 (437 female [45.1%] and 531 male [54.9%]; 468 patients aged <4 years) received a PPM due to postoperative heart block. The rate of CHS and postoperative PPM implantations increased by 2.2% and 7.2% per year between 1960 and 2018, respectively. In pediatric patients younger than 4 years with PPM implantation, the mean (SD) 20-year estimated direct and indirect costs from Markov model simulations were $180 664 ($32 662) and $15 939 ($1916), respectively. Using follow-up data of selected patients with clinical courses involving 1 or more complication events, the mean (SD) direct and indirect costs were $472 774 ($212 095) and $36 429 ($16 706), respectively. Conclusions and Relevance: In this economic evaluation study, the cost of PPM implantation in pediatric patients was found to accumulate over the lifespan. This cost may represent not only a substantial financial burden but also a health care burden to patient families. Reducing the incidence of PPM implantation should be a focused goal of CHS.

Systematic Mapping of Conduction Tissue Regions During Congenital Heart Surgery.

PURPOSE: Damage to the cardiac conduction system is a major risk of congenital cardiac surgery. Localization of the conduction system is commonly based on anatomic landmarks, which are variable in congenital heart diseases. We introduce a novel technique for identification of conduction tissue regions based on real-time fiberoptic confocal microscopy. DESCRIPTION: We developed a fiberoptic confocal microscopy-based technique to document conduction tissue regions and deployed it in pediatric patients undergoing repair of common congenital heart defects. The technique applies clockface schematics for intraoperative documentation of the location of conduction tissue regions. EVALUATION: We created clockface schematics for 11 patients with ventricular septal defects, 6 with tetralogy of Fallot, and 10 with atrioventricular canal defects. The approach revealed substantial variability in the location of the conduction system in hearts with congenital defects. The clockface schematics were used to create plans for subsequent surgical repair. CONCLUSIONS: The clockface schematic provides a reliable fiducial system to document and communicate variability of conduction tissue regions in the heart and applies this information for decision-making during congenital cardiac surgery.

Patch augmentation of small ascending aorta during stage I procedure reduces the risk of morbidity and mortality.

OBJECTIVES: Hypoplastic left heart syndrome (HLHS) with aortic atresia (AA) patients are prone to coronary insufficiency due to a small ascending aorta. Prophylactic patch augmentation of the small ascending aorta during the stage I procedure (S1P) may reduce the risk of coronary insufficiency as marked by ventricular dysfunction, need for extracorporeal membrane oxygenator (ECMO) support or mortality. METHODS: Retrospective analysis of patients with HLHS with AA who underwent an S1P was completed. Baseline ascending aorta size, right ventricular (RV) function and outcome variables of transplant-free survival, ECMO support after the stage 1 operation and RV function at the time of the bidirectional Glenn and latest follow-up were collected. RESULTS: Between January 2010 and April 2020, 11 patients underwent prophylactic ascending aorta augmentation at the time of the S1P as a planned portion of the procedure. A total of 125 patients underwent S1P during this period as a comparison. Overall survival was 100% for the augmented group and 74% for the control group (P = 0.66). A composite end point of transplant-free survival, no post-S1P ECMO and less than moderate RV dysfunction was created. At the time of BDG, this composite end point was 100% for the augmented group and 61.8% for the control group (P = 0.008) and at most recent follow-up was 100% for the augmented group and 59.3% for control (P = 0.007). Eight patients required a rescue procedure for the clinical evidence of coronary insufficiency following S1P that included ascending aorta patch augmentation or stent placement. When comparing these rescue versus prophylactic ascending aortic augmentations, there were also differences in the composite outcome 100% for augmented and 60% for rescue (P = 0.009) and at the time of most recent follow-up 100% for augmented and 50% for rescue (P = 0.029). CONCLUSIONS: Prophylactic patch augmentation of the ascending aorta in HLHS patients with AA may reduce the risk of mortality, ECMO and reduced RV function. Patients not initially undergoing augmentation but then requiring a rescue procedure have particularly poor outcomes. Patch augmentation for smaller ascending aortic diameters should be considered and further clinical experience may help delineate aorta diameter threshold for augmentation.

Toward cardiac tissue characterization using machine learning and light-scattering spectroscopy.

SIGNIFICANCE: The non-destructive characterization of cardiac tissue composition provides essential information for both planning and evaluating the effectiveness of surgical interventions such as ablative procedures. Although several methods of tissue characterization, such as optical coherence tomography and fiber-optic confocal microscopy, show promise, many barriers exist that reduce effectiveness or prevent adoption, such as time delays in analysis, prohibitive costs, and limited scope of application. Developing a rapid, low-cost non-destructive means of characterizing cardiac tissue could improve planning, implementation, and evaluation of cardiac surgical procedures. AIM: To determine whether a new light-scattering spectroscopy (LSS) system that analyzes spectra via neural networks is capable of predicting the nuclear densities (NDs) of ventricular tissues. APPROACH: We developed an LSS system with a fiber-optics probe and applied it for measurements on cardiac tissues from an ovine model. We quantified the ND in the cardiac tissues using fluorescent labeling, confocal microscopy, and image processing. Spectra acquired from the same cardiac tissues were analyzed with spectral clustering and convolutional neural networks (CNNs) to assess the feasibility of characterizing the ND of tissue via LSS. RESULTS: Spectral clustering revealed distinct groups of spectra correlated to ranges of ND. CNNs classified three groups of spectra with low, medium, or high ND with an accuracy of 95.00 ± 11.77 % (mean and standard deviation). Our analyses revealed the sensitivity of the classification accuracy to wavelength range and subsampling of spectra. CONCLUSIONS: LSS and machine learning are capable of assessing ND in cardiac tissues. We suggest that the approach is useful for the diagnosis of cardiac diseases associated with changes of ND, such as hypertrophy and fibrosis.

Super Glenn for staged biventricular repair: impact on left ventricular growth?

OBJECTIVES: The Super Glenn procedure involves targeted increased in blood flow to left sided heart structures with fenestrated atrial septation. The objective of this study was to examine the outcomes of patients who had this procedure as a part of biventricular staging and specifically evaluate the effect on dimensions of left heart structures. METHODS: Data for patients who had this procedure between 2005 and 2019 were retrospectively identified. RESULTS: Thirty-seven patients were identified. Most common diagnosis was hypoplastic left heart syndrome in 40% (n = 15). On echocardiography, the median mitral valve z score was -2.26. On cardiac magnetic resonance imaging, median indexed left ventricular end-diastolic volume was 31.5 ml/m2 and mitral/tricuspid inflow ratio was 0.35. The median age at Super Glenn was 2.3 years (interquartile range 1.5-3.6) while median weight was 12 kg (interquartile range 9.8-14). There were no early/hospital deaths. The median intensive care unit length of stay was 4 days, and median hospital length of stay was 10 days. Median follow-up for the entire cohort was 3 years (range 15 days to 13.2 years). There was a statistically significant increase in indexed left ventricular dimensions. There were 5 deaths (14%). Three patients (8%) underwent heart transplant. Freedom from death/transplant was 79% at 5 years. Seven patients (19%) needed a reoperation. Twenty-three patients (62%) underwent biventricular conversion after a median of 11.3 months after Super Glenn. CONCLUSIONS: The Super Glenn procedure achieves consistent increase in left ventricular dimensions. This may be a useful strategy to help achieve a successful biventricular circulation in patients with borderline left ventricle. The superiority/non-inferiority of this approach over the conventional Fontan pathway is unclear.

Toward detection of conduction tissue during cardiac surgery: Light at the end of the tunnel?

Postoperative conduction block requiring lifetime pacemaker placement continues to be a considerable source of morbidity for patients undergoing repair of congenital heart defects. Damage to the cardiac conduction system (CCS) during surgical procedures is thought to be a major cause of conduction block. Intraoperative identification and avoidance of the CCS is thus a key strategy to improve surgical outcomes. A number of approaches have been developed to avoid conduction tissue damage and mitigate morbidity. Here we review the historical and contemporary approaches for identification of conduction tissue during cardiac surgery. The established approach for intraoperative identification is based on anatomic landmarks established in extensive histologic studies of normal and diseased heart. We focus on landmarks to identify the sinus and atrioventricular nodes during cardiac surgery. We also review technologies explored for intraoperative tissue identification, including electrical impedance measurements and electrocardiography. We describe new optical approaches, in particular, and optical spectroscopy and fiberoptic confocal microscopy (FCM) for identification of CCS regions and working myocardium during surgery. As a template for translation of future technology developments, we describe research and regulatory pathways to translate FCM for cardiac surgery. We suggest that along with more robust approaches to surgeon training, including awareness of fundamental anatomic studies, optical approaches such as FCM show promise in aiding surgeons with repairs of heart defects. In particular, for complex defects, these approaches can complement landmark-based identification of conduction tissue and thus help to avoid injury to the CCS due to surgical procedures.

Intraoperative localization of cardiac conduction tissue regions using real-time fibre-optic confocal microscopy: first in human trial.

OBJECTIVES: The aim of this study was to evaluate the feasibility and safety of fibre-optic confocal microscopy (FCM) using fluorescein sodium dye for the intraoperative location of conduction tissue regions during paediatric heart surgery. METHODS: The pilot study included 6 patients undergoing elective surgery for the closure of isolated secundum atrial septal defect aged 30 days to 21 years. FCM imaging was integrated within the normal intraoperative protocol for atrial septal defect repair. Fluorescein sodium dye was applied on the arrested heart. FCM images were acquired at the atrioventricular node region, sinus node region and right ventricle (RV). Total imaging time was limited to 3 min. Any adverse events related to the study were recorded and analysed. Subjects received standard postoperative care. Trained reviewers (n = 9) classified, de-identified and randomized FCM images (n = 60) recorded from the patients as presenting striated, reticulated or indistinguishable microstructures. The reliability of reviewer agreement was assessed using Fleiss' kappa. RESULTS: The FCM imaging instruments were integrated effectively into the cardiac surgery operating room. All adverse events found in the study were deemed expected and not related to FCM imaging. Reticulated myocardial microstructures were found during FCM imaging at atrioventricular node and sinus node regions, while striated microstructures were observed in RV. Reliability of agreement of reviewers classifying the FCM images was high (Fleiss' kappa: 0.822). CONCLUSIONS: FCM using fluorescein sodium dye was found to be safe for use during paediatric heart surgery. The study demonstrates the potential for FCM to be effective in identifying conduction tissue regions during congenital heart surgery. CLINICAL TRIAL REGISTRATION NUMBER: NCT03189134.

Pediatric Airway Stent Designed to Facilitate Mucus Transport and Atraumatic Removal.

OBJECTIVE: The goal was to develop a pediatric airway stent for treating tracheobronchomalacia that could be used as an alternative to positive pressure ventilation. The design goals were for the stent to allow mucus flow and to resist migration inside the airways, while also enabling easy insertion and removal. METHODS: A helical stent design, together with insertion and removal tools, is presented. A mechanics model of stent compression is derived to assist in selecting stent design parameters (pitch and wire diameter) that provide the desired amount of tracheal support, while introducing the minimal amount of foreign material into the airway. Worst-case airway area reduction with stent support is investigated experimentally using a pressurized tracheal phantom matched to porcine tracheal tissue properties. The stent design is then evaluated in a porcine in vivo experiment. RESULTS: Phantom testing validated the mechanics model of stent compression. In vivo testing demonstrated that the stent was well tolerated by the animal. Since the helical design covers only a small portion of the epithelium, mucus transport through the stented region was minimally impeded. Furthermore, the screw-like stent resisted migration, while also providing for atraumatic removal through the use of an unscrewing motion during removal. CONCLUSION: The proposed stent design and tools represent a promising approach to prevent airway collapse in children with tracheobronchomalacia. SIGNIFICANCE: The proposed technology overcomes the limitations of existing airway stents and may provide an alternative to maintaining children on a ventilator.