Absorbable metal stents for vascular use in pediatric cardiology: progress and outlook.

The past five years have yielded impressive advancements in fully absorbable metal stent technology. The desired ultimate ability for such devices to treat a vascular stenosis without long-term device-related complications or impeding future treatment continues to evoke excitement in clinicians and engineers alike. Nowhere is the need for fully absorbable metal stents greater than in patients experiencing vascular anomalies associated with congenital heart disease (CHD). Perhaps not surprisingly, commercially available absorbable metal stents have been implanted in pediatric cardiology patients with conditions ranging from pulmonary artery and vein stenosis to coarctation of the aorta and conduit/shunt reconstructions. Despite frequent short term procedural success, device performance has missed the mark with the commercially available devices not achieving degradation benchmarks for given applications. In this review we first provide a general overview detailing the theory of absorbable metal stents, and then review recent clinical use in CHD patients since the release of current-generation absorbable metal stents around 2019. We also discuss the challenges and our center's experience associated with the use of absorbable metal stents in this pediatric population. Lastly, we present potential directions for future engineering endeavors to mitigate existing challenges.

Establishing Carotid Seldinger as Routine Access in Infants; Planning, Performance, and Follow-Up Protocols.

Percutaneous carotid access (PCA) in infants has been reported in small multicenter cohorts, case reports and wider studies over the last 20 years. Compare outcomes after implementation of a systematic approach to PCA in a single center including an imaging follow-up protocol. Retrospective case-control study of PCA at Children's Hospital Colorado was performed from January 2013 to December 2022. Seventy-four patients underwent 82 PCAs for cardiac catheterization. The median age (range) was 14 days (1-359), and weight was 3.25-kg (1.9-7.9). Median sheath size was 4-Fr (3.3-6). Seventy-seven interventions performed included PDA stenting, aortic valvoplasty, BTT shunt stenting, and coarctation stenting. Vascular access was performed using a modified 21 g butterfly needle. A protocolized approach was implemented in 2020 reversing the patient head-to-toe orientation on the catheterization table, maintaining intubation and sedation for 4-h during recovery and routine use of a specific vascular ultrasound protocol. Following these changes, time to access significantly improved with no major complications. Before 2020, two access related complications occurred. One requiring surgical vascular repair and one occlusive thrombus. A significant increase in sheath time in post-era was associated with increased case complexity. Longer sheath times were not associated with increased risk of vessel injury or thrombus. No neurological insults were reported. Our experience confirms that PCA is safe and achievable with preserved vessel patency regardless of patient weight or sheath size. A protocolized planning, recovery, and follow-up regimen is recommended to establish safe practice and identify and treat complications as necessary.

Clinical Variables Associated with Pre-Fontan Aortopulmonary Collateral Burden.

Aortopulmonary collaterals (APCs) develop universally, but to varying degrees, in patients with single ventricle congenital heart disease (CHD). Despite their ubiquitous presence, APCs remain poorly understood. We sought to evaluate the association between APC burden and common non-invasive clinical variables. We conducted a single center, retrospective study of patients with single ventricle CHD and previous Glenn palliation who underwent pre-Fontan cardiac magnetic resonance (CMR) imaging from 3/2018 to 3/2021. CMR was used to quantify APC flow, which was normalized to aortic (APC/QAo) and pulmonary vein (APC/QPV) blood flow. Univariate, multivariable, and classification and regression tree (CART) analyses were done to investigate the potential relationship between CMR-quantified APC burden and clinical variables. A total of 29 patients were included, all of whom had increased APC flow (APC/QAo: 26.9, [22.0, 39.1]%; APC/QPV: 39.4 [33.3, 46.9]%), but to varying degrees (APC/QAo: range 11.9-44.4%; APC/QPV: range 17.7-60.0%). Pulmonary artery size (Nakata index, at pre-Fontan CMR) was the only variable associated with APC flow on multivariable analysis (APC/QAo: p = 0.020, R2 = 0.19; APC/QPV: p = 0.0006, R2 = 0.36) and was the most important variable associated with APC burden identified by CART analysis (size inversely related to APC flow). APC flow is universally increased but highly variable in patients with single ventricle CHD and Glenn circulation. Small branch pulmonary artery size is a key factor associated with increased APC burden; however, the pathogenesis of APCs is likely multifactorial. Further research is needed to better understand APC pathogenesis, including predisposing and mitigating factors.

Left ventricular function before and after percutaneous patent ductus arteriosus closure in preterm infants.

BACKGROUND: Definitive closure of the patent ductus arteriosus (PDA) is associated with significant changes in the loading conditions of the left ventricle (LV), which may lead to cardiovascular and respiratory instability. The objective of the study was to evaluate targeted neonatal echocardiography (TnECHO) characteristics and the clinical course of preterm infants ≤2 kg undergoing percutaneous PDA closure. METHODS: Retrospective cohort study of prospectively acquired pre- and post-closure TnECHOs to assess hemodynamic changes. Cardiorespiratory parameters in the first 24 h following PDA closure were also evaluated. RESULTS: Fifty patients were included with a mean age of 30.6 ± 9.6 days and weight of 1188 ± 280 g. LV global longitudinal strain decreased from -20.6 ± 2.6 to -14.9 ± 2.9% (p < 0.001) after 1 h. There was a decrease in LV volume loading, left ventricular output, LV systolic and diastolic parameters. Cardiorespiratory instability occurred in 24 (48%) [oxygenation failure in 44%] but systolic hypotension and/or need for cardiovascular medications was only seen in 6 (12%). Patients with instability had worse baseline respiratory severity score and lower post-closure early diastolic strain rates. CONCLUSIONS: Percutaneous PDA closure leads to a reduction in echocardiography markers of LV systolic/diastolic function. Post-closure cardiorespiratory instability is characterized primarily by oxygenation failure and may relate to impaired diastolic performance. IMPACT: Percutaneous patent ductus arteriosus closure leads to a reduction in echocardiography markers of left ventricular volume loading, cardiac output, and left ventricular systolic/diastolic function. Post-procedural cardiorespiratory instability is characterized primarily by oxygenation failure. Post-procedural cardiorespiratory instability may relate to impaired diastolic performance.

Abnormal flow conduction through pulmonary arteries is associated with right ventricular volume and function in patients with repaired tetralogy of Fallot: does flow quality affect afterload?

OBJECTIVES: Flow through the proximal pulmonary arteries (PAs) of patients with repaired Tetralogy of Fallot (TOF) is known to be highly disordered and associated with significant regurgitation. The purpose of this study was to evaluate 4D-Flow MRI-derived viscous energy loss [Formula: see text])-as a result of non-efficient flow propagation, and relate this parameter to standard right ventricular (RV) size and function markers in patients with repaired TOF. METHODS: Thirty-five patients with TOF and 14 controls underwent comprehensive 4D-Flow MRI evaluation for qualitative flow analysis and to calculate [Formula: see text] in the main and right pulmonary arteries. Sampled [Formula: see text] indices were correlated with the MRI-derived RV size and functional indices. RESULTS: All patients with TOF exhibited abnormal, supra-physiologic helical/vortical formations in the PAs. Patients with TOF had significantly increased peak systolic [Formula: see text] (8.0 vs 0.5 mW, p < 0.001), time-averaged [Formula: see text] (2.5 vs. 0.2 mW, p < 0.001), and peak systolic [Formula: see text] indexed to stroke volume (0.082 vs. 0.012 mW/mL, p < 0.001). [Formula: see text] indexed to stroke volume correlated with the RV end-diastolic volume (R = 0.68, p < 0.001), end-systolic volume (R = 0.62, p < 0.001), ejection fraction (R = -0.45, p = 0.002), and cardiac index (R = 0.45, p = 0.002). The mean estimated energy loss due to [Formula: see text] with regard to input RV mechanical power was 4.7%. CONCLUSION: This study demonstrates that patients with repaired TOF have highly abnormal flow conduction through the PAs which result into extensive viscous energy loss. This significant flow-mediated energy loss is associated with the RV volume and function, and might represent considerable loss of mechanical power generated by each cardiac cycle. Future studies are required to assess whether the abnormal flow conduction adds to the RV afterload and remodeling. KEY POINTS: • Abnormal flow patterns through proximal pulmonary arteries in patients with TOF are associated with excessive viscous energy loss. • Inefficient flow conduction is associated with the RV dilation and reduced function and might contribute to the RV adaptive remodeling.

In vitro performance of Lifetech IBS Angel™ (iron-based bioresorbable scaffold) stents during overdilation for use in pediatric patients.

Objectives: The objective of this study was to assess the mechanical performance of the Lifetech IBS Angel stents during overdilation as is often required in pediatric applications; including time of first fracture, foreshortening, and the type of fracturing that occurs. Materials and methods: In vitro testing was performed and repeated for each stent three times under physiologic conditions with continuous audiovisual imaging allowing for post-testing evaluations. Assessment of sheath fit was also completed. Results: A total of 47 stents on monorail system were overdilated to complete fracture after passing through either a 4 or 5 French sheath. First strut fracture occurred in 4 and 6 mm stents when they reached greater than 50% overexpansion. Larger stents could achieve at least 30% increased diameter prior to first strut fracture. No fragmentation of any of the stents was seen throughout testing. Conclusion: The IBS Angel has thin struts allowing for a lower profile with increased maneuverability and use with smaller sheaths. Embolization potential of strut fragments was not seen. Increased diameter well beyond design parameters was seen in all with acceptable foreshortening.

Feasibility, Safety, and Short-Term Outcomes of Transcatheter Patent Ductus Arteriosus Closure in Premature Infants on High-Frequency Jet Ventilation.

Background Prolonged exposure to a hemodynamically significant patent ductus arteriosus (PDA) is associated with major morbidity, particularly in infants born at <27 weeks' gestation. High-frequency jet ventilation (HFJV) is a standard of care at our center. There are no data about transcatheter PDA closure while on HFJV. The aim of this study was to assess the feasibility, safety, and outcomes of HFJV during transcatheter PDA closure. Methods and Results This is a retrospective cohort study of premature infants undergoing transcatheter device closure on HFJV. The primary outcome was successful device placement. Secondary outcomes included procedure time, fluoroscopy time and dose, time off unit, device complications, need for escalation in respiratory support, and 7-day survival. Subgroup comparative evaluation of patients managed with HFJV versus a small cohort of patients managed with conventional mechanical ventilation was performed. Thirty-eight patients were included in the study. Median age and median weight at PDA device closure for the HFJV cohort were 32 days (interquartile range, 25.25-42.0 days) and 1115 g (interquartile range, 885-1310 g), respectively. There was successful device placement in 100% of patients. There were no device complications noted. The time off unit and the procedure time were not significantly different between the HFJV group and the conventional ventilation group. Infants managed by HFJV had shorter median fluoroscopy times (4.5 versus 6.1 minutes; P<0.05) and no increased risk of adverse respiratory outcomes. Conclusions Transcatheter PDA closure in premature infants on HFJV is a safe and effective approach that does not compromise device placement success rate and does not lead to secondary complications.

Cardiac Magnetic Resonance to Predict Coronary Artery Compression in Transcatheter Pulmonary Valve Implantation Into Conduits.

OBJECTIVES: The aim of this study was to evaluate the accuracy of cardiac magnetic resonance (CMR) in predicting coronary artery (CA) compression during transcatheter pulmonary valve implantation (TPVi). BACKGROUND: TPVi is a widely available option to treat dysfunctional right ventricle (RV)-to-pulmonary artery (PA) conduits, but CA compression is an absolute contraindication. CMR can evaluate coronary anatomy, but its utility in predicting CA compression is not well established. METHODS: After Institutional Review Board approval was obtained, all patients at 9 centers with attempted TPVi in RV-PA conduits and recent CMR (≤12 months) were analyzed. A core laboratory reviewed all CMR studies for the shortest orthogonal distance from a CA to the conduit, the shortest distance from a CA to the most stenotic area of the conduit, and subjective assessment of CA compression risk. RESULTS: Among 231 patients, TPVi was successful in 198 (86%); in 24 (10%), balloon testing precluded implantation (documented CA compression or high risk). Distance to the RV-PA conduit ≤2.1 mm (area under the curve [AUC]: 0.70) and distance to most stenotic area ≤13.1 mm (AUC: 0.69) predicted CA compression. Subjective assessment had the highest AUC (0.78), with 96% negative predictive value. Both distances and qualitative assessment remained independently associated with CA compression when controlling for abnormal coronary anatomy or degree of conduit calcification. CONCLUSIONS: CMR can help predict the risk for CA compression during TPVi in RV-PA conduits but cannot completely exclude CA compression. CMR may assist in patient selection and counseling families prior to TPVi, although balloon testing remains essential.

This and that: management of Tetralogy of Fallot and pulmonary vein stenosis in an infant-a case report.

BACKGROUND: Tetralogy of Fallot (TOF) is the most common congenital cyanotic cardiac lesion. Pulmonary vein stenosis occurs much less commonly and remains difficult to manage. It is exceedingly uncommon for a patient to have both lesions. This case highlights the diagnostic and management difficulties in an infant with these two lesions. CASE SUMMARY: The patient is a 4-month-old female infant with a history of TOF status post right ventricular outflow tract stent placement who presented after a hypoxaemic event at home to 40% SpO2. Computed tomography angiography demonstrated previously undiagnosed pulmonary vein stenosis of all four veins. She underwent multiple catheter-based palliations including balloon dilations and stent placements in each pulmonary vein in order to maximize her chances of successful definitive repair. She underwent successful repair of her TOF and pulmonary vein stenosis at ten months of age. DISCUSSION: The combination of TOF and pulmonary vein stenosis is not common, but when these lesions co-occur, they present a significant dilemma in determining the timing of surgery in order to optimize the odds of a successful outcome. This case demonstrates that serial catheter-based procedures can be valuable tools in minimizing pre-operative risk factors and highlights one strategy in determining timing of definitive surgical repair.