Transcatheter Fontan completion: Creation of an extracardiac Fontan.

Patients with functionally univentricular hearts are usually palliated surgically. There have been several reports of successful attempts to complete the Fontan procedure without surgery. The pathways created at the time of the preconditioning were largely reminiscent of the lateral tunnel Fontan. However, this approach is still confidentially limited to a small number of centers. In 2013, we designed a circuit that mimics the actual surgical technique of extracardiac total cavopulmonary connection to allow for transcatheter completion in an animal study. A polytetrafluoroethylene conduit was connected between the pulmonary artery and the inferior vena cava (IVC). The superior anastomosis was occluded to avoid flow between IVC and superior vena cava (SVC). The conduit was connected to the right atrium (RA) and a large fenestration was created to allow free flow from the IVC to the RA. Extrapolating our approach, a center reported the successful transcatheter completion of an extracardiac Fontan in a 6-year-old child. However, this technique is not directly transposable to our population of patients who require preconditioning in infancy. We report here an innovative extension of this technique that may allow preparing patients in infancy, ideally at the time of the Glenn in the future, to receive an extracardiac Fontan at 2 years/11 kg without additional surgery.

Multicenter Experience for Early and Mid-Term Outcome of MyVal Transcatheter Pulmonary Valve Implantation.

Transcatheter pulmonary valve implantation (TPVI) is a surgical alternative for correcting dysfunctional right ventricular outflow tract in previously operated patients. MyVal transcatheter heart valve (THV) (Meril Life Sciences, India), a new transcatheter valve designed for aortic position has recently been reported to be implanted in pulmonary position. Myval transcatheter valve were implanted in patients with stenosed dysfunctional conduits, severe regurgitation from transannular patch or dysfunctional surgical pulmonary valves (Bioprosthesis). Procedural details and post-TPVI follow-up were analysed. Myval TPVI was used in Fifty three patients with median age of 15 years (IQR 12-19.5 years). Almost sixty percent of the patients were male, with a median weight of 50 kg (31-63 kg). Prestenting was used in more than 80 percent of patients (n = 45 patients), while 6 patients had a prior surgical valve implantation. After Myval TPVI implantation, the peak instantaneous gradient across the RVOT decreased from a median of 23.5 mmHg (IQR 10-53 mmHg) pre-procedure to 10 mmHg (IQR 5-16 mmHg) post-procedure. The median fluoroscopy time for the procedure was 35 min (IQR 23.5-44 min). The large sizes-mainly the 29-mm and 32 mm Myval (Navigator, Meril Life Sciences Pvt Ltd, India), were the most used size in 40% (n = 22) of the cases each. The median contrast volume used during the procedure was 247 mL (IQR 120-300 mL). Patients were followed for a median period of 360 days (IQR 164-525 days). At the last clinic follow-up, there was no tricuspid valve regurgitation. Moderate neo-pulmonary valve regurgitation was reported in three cases. Early experience of TPVI with MyVal is encouraging with procedural success in all patients and acceptable mid-term outcomes.

Transcatheter Closure of Superior Sinus Venosus Defects.

Superior sinus venosus defect is a communication between the right and left atrium located above the upper margin of the oval fossa, immediately inferior to the junction of the superior vena cava and the right atrium. It is systematically associated with partial anomalous pulmonary venous drainage, especially of the right upper pulmonary vein. Surgical repair has been the gold standard approach to close that defect. Introduced in 2014, percutaneous closure has gradually become a safe and effective alternative to surgery in carefully selected patients, although worldwide experience remains limited. This article provides an appraisal of the patients' selection process and a step-by-step description of the procedure as well as a comprehensive review of its outcomes.

Three centers experience with device closure of congenital Gerbode-type perimembranous ventricular septal defects.

OBJECTIVES: We aim to evaluate our experience with interventional closure of Gerbode-type perimembranous ventricular septal defects (pmVSDs). METHODS: We performed three-center retrospective data review of patients with congenital indirect Gerbode-type pmVSDs treated percutaneously between August 2017 and May 2021. Standard safety and latest follow-up outcomes were assessed. RESULTS: Ten patients (six females) were identified with a median age of 6.8 years (range: 2.5-54) and a median weight of 26.5 kg (range: 12-88). The median left ventricular defect size was 10 mm (range: 3-15.5). On baseline ultrasound, 6 patients had absent subaortic rim , 6 patients had trivial aortic regurgitation, and 3 patients had tear-drop-type (small) aortic cusp prolapse. The tricuspid regurgitation was graded II (n = 5) and III (n = 5). Five Lifetech Konar-Multifunctional occluders, four Amplatzer duct occluders II and one Amplatzer duct occluder I were implanted. The median fluoroscopy time was 10.4 min (range: 4.3-20.2). Pre-existing aortic regurgitations remained identical. One new aortic regurgitation was identified before discharge and remained trivial after 48 months of follow-up. No heart block or tricuspid stenosis was observed on a median follow-up of 17 months (range: 3-48). All patients are symptom-free with complete shunt closure and significant regression or resolution of tricuspid regurgitation. CONCLUSIONS: Despite anatomical challenges, interventional closure of congenital indirect Gerbode-type pmVSD appears to be feasible, safe, and most importantly clinically effective using different commercially available devices. Amplatzer duct occluder II and Lifetech Konar-Multifunctional occluder offer interesting specifications to retrogradely target this specific defect with success.

Multiscale modelling of Potts shunt as a potential palliative treatment for suprasystemic idiopathic pulmonary artery hypertension: a paediatric case study.

Potts shunt (PS) was suggested as palliation for patients with suprasystemic pulmonary arterial hypertension (PAH) and right ventricular (RV) failure. PS, however, can result in poorly understood mortality. Here, a patient-specific geometrical multiscale model of PAH physiology and PS is developed for a paediatric PAH patient with stent-based PS. In the model, 7.6mm-diameter PS produces near-equalisation of the aortic and PA pressures and [Formula: see text] (oxygenated vs deoxygenated blood flow) ratio of 0.72 associated with a 16% decrease of left ventricular (LV) output and 18% increase of RV output. The flow from LV to aortic arch branches increases by 16%, while LV contribution to the lower body flow decreases by 29%. Total flow in the descending aorta (DAo) increases by 18% due to RV contribution through the PS with flow into the distal PA branches decreasing. PS induces 18% increase of RV work due to its larger stroke volume pumped against lower afterload. Nonetheless, larger RV work does not lead to increased RV end-diastolic volume. Three-dimensional flow assessment demonstrates the PS jet impinging with a high velocity and wall shear stress on the opposite DAo wall with the most of the shunt flow being diverted to the DAo. Increasing the PS diameter from 5mm up to 10mm results in a nearly linear increase in post-operative shunt flow and a nearly linear decrease in shunt pressure-drop. In conclusion, this model reasonably represents patient-specific haemodynamics pre- and post-creation of the PS, providing insights into physiology of this complex condition, and presents a predictive tool that could be useful for clinical decision-making regarding suitability for PS in PAH patients with drug-resistant suprasystemic PAH.

Comparison of Two Percutaneous Atrial Septal Defect Occluders for Device Healing and Nickel Release in a Chronic Porcine Model.

AIMS: To investigate the healing process and nickel release of the Hyperion occluder (Comed BV, Netherlands), as compared to the Amplatzer septal occluder (ASO) (St. Jude Medical Inc., St. Paul, MN, USA) in a chronic swine model. BACKGROUND: Some long-term complications occurring after percutaneous atrial septal defect (ASD) closure may be partially associated with an inappropriate healing of the device and increased nickel release. There is no direct comparative study of different occluders for healing and nickel release. METHODS: After percutaneous ASD creation, 12 pigs were implanted with 15 mm Hyperion (n = 6) and 15 mm ASO (n = 6) devices. After 1 month (n = 3 for each device) and 3 months (n = 3 for each device) of follow-up, device explantation was performed and healing was assessed using histopathological workup. Systemic and tissular nickel release was performed. RESULTS: Implantation was successful in 100% without complications. Device coverage was observed as early as 1 month after implantation and was almost complete after 3 months. A granulation tissue with a predominantly mononuclear inflammatory reaction was observed in contact with nitinol wires while an inflammatory reaction was seen in contact with textile fibers. We found no statistically significant difference between the 2 devices whether for histological grading scores or systemic nickel release, regardless to follow-up duration. CONCLUSIONS: In this preclinical study, we demonstrated that Amplatzer septal occluder and Hyperion occluder were not significantly different for device healing and nickel release processes.

Percutaneous closure of patent ductus arteriosus in premature infants: A French national survey.

BACKGROUND: Transcatheter closure of patent ductus arteriosus (PDA) in premature infants has been shown to be feasible in small series. Outcomes in larger series are currently lacking. MATERIAL: All premature infants (< 36 weeks GA) who underwent transcatheter PDA closure were included in a multicenter French national survey. Demographic data (gestational age [GA], birth weight [BW]) and procedural data (weight [PW], age at procedure [AP], procedural success, fluoroscopy time, and type of device) were collected. Outcomes and procedural complications were reviewed. RESULTS: Between September 2013 and June 2017, 102 patients were included. In 71 cases, PDA pharmacological closure had been attempted. Mean GA was 27 ± 2.9 weeks. Mean BW and PW were 1,040 ± 715 g and 1,543 ± 698 g, respectively. Mean AP was 39 ± 26 days. Number of premature infants <1 kg, between 1 and 2 kg, and > 2 kg was 21, 59, and 22, respectively. Mean fluoroscopic time was 6.5 min. Success rate was 99%. Device- or procedure-related complications were reported in nine patients (8.9%) including three LPA stenoses (requiring surgery in two and balloon dilatation in one), two neo-coarctations (one requiring subsequent surgery), and three instances of tricuspid valve regurgitation at follow-up. Seven deaths were reported, none being related to the procedure. Mean follow-up was 39.75 ± 13.1 months. CONCLUSION: In this large series of premature infants undergoing transcatheter PDA closure, it was demonstrated that this procedure can be performed successfully in the vast majority of patients with an acceptable complication rate. Future efforts should focus on minimizing complications, particularly device-related vascular stenoses.

Transcatheter ductus arteriosus stenting in paediatric cardiology: Indications, results and perspectives.

Stenting the arterial duct emerged in the early 1990s as an alternative to a variety of surgical interventions in neonates with a duct-dependent pulmonary or systemic circulation complex defect. Furthermore, palliative ductal stenting has been applied in older children with severe suprasystemic pulmonary arterial hypertension, as an alternative to surgical shunts, such as Potts anastomosis. Early results of this technique were discouraging, but by learning from the failures of the past, ductal stenting has become a reliable palliative therapy. In this review, we aim to describe the historical evolution of ductal stenting, its different clinical applications and outcomes, and future perspectives for this strategy in congenital cardiac catheterization.

Effects of reducing frame rate from 7.5 to 4 frames per second on radiation exposure in transcatheter atrial septal defect closure.

OBJECTIVES: The aim of this study was to evaluate the reduction of frame rate from 7.5 to 4 frames per second on radiation exposure and to provide new standards of radiation exposure. BACKGROUND: Frame rate is a large contributor to radiation exposure. The use of 4 frames per second for closure of atrial septal defects has been reported not to affect the level of radiation exposure. METHODS: We retrospectively reviewed radiation data from all patients referred to our catheterisation laboratory for closure of an atrial septal defect between January, 2015 and June, 2017. Fluoroscopic time, dose area product (µGy.m2), and total air kerma (mGy) were collected. These values were compared according to the frame rate used for closure of atrial septal defects. RESULTS: A total of 49 atrial septal defects were closed using 7.5 frames per second and 85 using 4 frames per second. Baseline characteristics were similar in both groups. Procedural success was similar in both groups (100 versus 98.8%). Median total air kerma and dose area product were statistically lower in the 4 frames per second group (4 versus 1.3 mGy [p=0.00012]), 43.7 versus 13.1 µGy.m2 [p0.05). CONCLUSION: Reduction of frame rate allows reducing significantly the radiation exposure while maintaining excellent clinical results in transcatheter closure of atrial septal defects. We recommend implementing this little change in every laboratory in order to achieve drastic reduction of radiation exposure to the patients and laboratory personnel.

French national survey on infective endocarditis and the Melody™ valve in percutaneous pulmonary valve implantation.

BACKGROUND: Percutaneous pulmonary valve implantation (PPVI) is a routine treatment for dysfunctional right ventricular outflow tract. Infective endocarditis (IE) is a major concern. AIM: To report French experience with the Melody™ valve (Medtronic Inc., Minneapolis, MN, USA). METHODS: All patients who underwent PPVI were recorded in a multicentre French national survey. Demographic and procedural data were collected from patients with IE. Bacterial identification, diagnostic tools and outcome were recorded. RESULTS: Forty-five cases of IE were diagnosed in 43 patients. The cumulative IE incidence was 11.8% (95% confidence interval [CI] 8.5-15.9). The annualized IE incidence was 3.6% (95% CI 0-4.8). Freedom from IE was 96.3% and 85.8% at 12 months and 60 months, respectively. IE incidence did not change during the study period. The mean interval between PPVI and IE was 2.6±2.1 years (range, 5 days to 7.3 years). Fifteen patients with IE required intravenous antibiotics only. Seven patients had early interventional cardiac catheterization to relieve severe right ventricular outflow tract obstruction. Twenty-four patients had surgical valve replacement (six urgently; nine semi-urgently; nine electively). Staphylococcus aureus IE required surgery in all but one patient. Three patients died before any treatment. Three additional patients died, giving a mortality rate of 14%. Global survival in the total cohort of patients who received a Melody valve was excellent (96.5% at 5 years). When comparing survival curves between the IE and non-IE groups, death and cardiovascular events were statistically significantly higher in the IE group (log-rank P<0.0001). CONCLUSION: Melody valve IE is a severe complication following PPVI. The annualized IE incidence in this cohort was similar to rates reported in other studies. With rapid diagnosis and adequate treatment, outcome has improved, and unfavourable outcome is mainly associated with S. aureus.

Radiation exposure in transcatheter patent ductus arteriosus closure: time to tune?

OBJECTIVES: The aims of this study were to describe radiation level at our institution during transcatheter patent ductus arteriosus occlusion and to evaluate the components contributing to radiation exposure. BACKGROUND: Transcatheter occlusion relying on X-ray imaging has become the treatment of choice for patients with patent ductus arteriosus. Interventionists now work hard to minimise radiation exposure in order to reduce risk of induced cancers. METHODS: We retrospectively reviewed all consecutive children who underwent transcatheter closure of patent ductus arteriosus from January 2012 to January 2016. Clinical data, anatomical characteristics, and catheterisation procedure parameters were reported. Radiation doses were analysed for the following variables: total air kerma, mGy; dose area product, Gy.cm2; dose area product per body weight, Gy.cm2/kg; and total fluoroscopic time. RESULTS: A total of 324 patients were included (median age=1.51 [Q1-Q3: 0.62-4.23] years; weight=10.3 [6.7-17.0] kg). In all, 322/324 (99.4%) procedures were successful. The median radiation doses were as follows: total air kerma: 26 (14.5-49.3) mGy; dose area product: 1.01 (0.56-2.24) Gy.cm2; dose area product/kg: 0.106 (0.061-0.185) Gy.cm2/kg; and fluoroscopic time: 2.8 (2-4) min. In multivariate analysis, a weight >10 kg, a ductus arteriosus width <2 mm, complications during the procedure, and a high frame rate (15 frames/second) were risk factors for an increased exposure. CONCLUSION: Lower doses of radiation can be achieved with subsequent recommendations: technical improvement, frame rate reduction, avoidance of biplane cineangiograms, use of stored fluoroscopy as much as possible, and limitation of fluoroscopic time. A greater use of echocardiography might even lessen the exposure.

Outcomes of Transcatheter Tricuspid Valve-in-Valve Implantation in Patients With Ebstein Anomaly.

We sought to describe the acute results and short- to medium-term durability of transcatheter tricuspid valve-in-valve (TVIV) implantation within surgical bioprostheses among patients with Ebstein anomaly (EA). Cases were identified from a voluntary, multicenter, international registry of 29 institutions that perform TVIV. Demographic, clinical, procedural, and follow-up data were analyzed. Eighty-one patients with EA underwent TVIV from 2008 to 2016. Thirty-four patients (42%) were New York Heart Association (NYHA) class 3/4 at time of TVIV. The most common indication for TVIV was the presence of moderate or severe tricuspid regurgitation (40%). Most patients received a Melody valve (64%). TVIV was ultimately successful in all patients, and there was no procedural mortality. Four patients (5%) developed acute valve thrombosis, 4 patients (5%) developed endocarditis, and 9 patients (11%) developed valve dysfunction not related to thrombosis or endocarditis. Eight patients (10%) underwent reintervention (2 transcatheter, 6 surgical) due to thrombosis (3), endocarditis (2), other valve dysfunction (2), and patient-prosthesis mismatch without valve dysfunction (1). Among 69 patients who were alive without reintervention at latest follow-up, 96% of those with NYHA status reported were class 1/2, a significant improvement from baseline (62% NYHA class 1/2, p <0.001). In conclusion, transcatheter TVIV offers a low-risk, minimally invasive alternative to surgical tricuspid valve re-replacement in patients with EA and a failing tricuspid valve bioprosthesis.

A new one-step procedure for pulmonary valve implantation of the melody valve: Simultaneous prestenting and valve implantation.

OBJECTIVES: To describe a new modification, the one-step procedure, that allows interventionists to pre-stent and implant a Melody valve simultaneously. BACKGROUND: Percutaneous pulmonary valve implantation (PPVI) is the standard of care for managing patients with dysfunctional right ventricular outflow tract, and the approach is standardized. METHODS: Patients undergoing PPVI using the one-step procedure were identified in our database. Procedural data and radiation exposure were compared to those in a matched group of patients who underwent PPVI using the conventional two-step procedure. RESULTS: Between January 2016 and January 2017, PPVI was performed in 27 patients (median age/range, 19.1/10-55 years) using the one-step procedure involving manual crimping of one to three bare metal stents over the Melody valve. The stent and Melody valve were delivered successfully using the Ensemble delivery system. No complications occurred. All patients had excellent hemodynamic results (median/range post-PPVI right ventricular to pulmonary artery gradient, 9/0-20 mmHg). Valve function was excellent. Median procedural and fluoroscopic times were 56 and 10.2 min, respectively, which significantly differed from those of the two-step procedure group. Similarly, the dose area product (DAP), and radiation time were statistically lower in the one-step group than in the two-step group (P < 0.001 for all variables). After a median follow-up of 8 months (range, 3-14.7), no patient underwent reintervention, and no device dysfunction was observed. CONCLUSIONS: The one-step procedure is a safe modification that allows interventionists to prestent and implants the Melody valve simultaneously. It significantly reduces procedural and fluoroscopic times, and radiation exposure.

Reduction of radiation exposure in transcatheter atrial septal defect closure: How low must we go?

BACKGROUND: Cardiac catheterization relies on X-ray imaging. Most procedures are now standardized. Interventionists must strive to minimize radiation exposure to reduce the risk of induced cancers. AIMS: To describe the radiation level in our institution, and evaluate the components contributing to radiation exposure, during transcatheter atrial septal defect (ASD) closure. METHODS: Radiation doses for ASD closure performed between January 2009 and November 2015 were reviewed retrospectively. Data on fluoroscopic time, dose area product (DAP), DAP/kg of body weight and total air kerma were collected. RESULTS: One hundred and seventy-four consecutive patients were included. Procedural success was 98.3%. Median procedural and fluoroscopic times were 15minutes and 1.2minutes, respectively. Median total air kerma, DAP and DAP/kg were 9.2 mGy, 88.3µGy.m2 and 3.2µGy.m2/kg, respectively. Risk factors associated with higher DAP were older age, larger ASD and device, need for balloon calibration, occurrence of complications and use of higher frame rate. Reduction of frame rate to 7.5 frames/second alone reduced by a factor of 2 the median DAP, DAP/kg and air kerma (99 vs 43µGy.m2, 3.5 vs 1.7µGy.m2/kg and 11 vs 4.8 mGy, respectively; P<0.001). CONCLUSIONS: A low dose of radiation can be achieved for transcatheter ASD closure, even in complex ASDs, by following these recommendations: reduction of frame rate; avoidance of lateral view and cine acquisition; and limitation of fluoroscopic time by avoiding unnecessary manoeuvres and using echocardiographic guidance as much as possible.

Percutaneous pulmonary valve implantation: what have we learned over the years?

Percutaneous pulmonary valve implantation has been widely accepted as an alternative to surgery in selected patients with right ventricular outflow tract (RVOT) dysfunction. This totally new field of our specialty pushed centres to rethink overall strategies on how to treat RVOT dysfunction. In this review, we will focus on challenges related to patient selection, and discuss innovative procedural techniques developed over the years to enlarge the number of candidates for the technique.

Safety and Feasibility of the Transcatheter Approach to Create a Reverse Potts Shunt in Children With Idiopathic Pulmonary Arterial Hypertension.

BACKGROUND: The reversed Potts shunt improves right ventricular (RV) function in patients with suprasystemic pulmonary arterial hypertension (PAH). The proximity of the left pulmonary artery (LPA) to the descending aorta (DAo) permits the creation of a transcatheter connection. We sought to assess the safety, feasibility, and hemodynamic efficacy of the transcatheter Potts shunt (TPS) in children. METHODS: The TPS procedure was performed using radiofrequency energy for vessel perforation and deployment of a covered stent to connect the DAo and LPA. Procedural details and clinical follow-up data were collected prospectively. RESULTS: A TPS was successfully created in 6 children (mean age, 11.0 ± 4.2 years) with drug-refractory suprasystemic PAH and deteriorating RV function. All patients exhibited nearly complete equalization of aortic and pulmonary pressures and improvement in RV contractility within days after TPS placement. Two patients with pre-existing severe biventricular dysfunction and pericardial effusion experienced acute low-output states immediately after shunt creation because of sudden reductions in left ventricular (LV) preload, resulting in cardiac arrest, irreversible brain damage, and death. Stent dislodgement and embolization into the iliac artery occurred in 1 patient. The stent was successfully secured and followed by placement of a second stent at the target location. The procedure was uncomplicated in 4 patients, who remain alive after a mean follow-up of 10 ± 2.6 months. Intravenous vasodilator therapy was weaned uneventfully after TPS in 3 patients. CONCLUSIONS: TPS creation in children is feasible and results in hemodynamic improvement. Further insights into high-risk markers, such as reduced preprocedural LV function and preload reserves, are important for guiding patient selection.

Percutaneous pulmonary Melody® valve implantation in small conduits.

BACKGROUND: The Melody® pulmonary valve has received approval for the treatment of dysfunctional right ventricular (RV) outflow tract conduits ≥16mm. AIMS: To investigate technical and clinical outcomes in patients who underwent percutaneous pulmonary valve implantation (PPVI) in conduits ≤16mm. METHODS: Eleven patients were enrolled retrospectively between 2000 and 2015 in a cardiac referral centre. RESULTS: The PPVI indications were obstruction (n=5); regurgitation (n=1); and mixed lesions (n=5). Pre-stenting was performed during the procedure in seven cases. Three of the remaining four patients had previous stent implantation. The mean maximal dilatation balloon diameter/surgical initial diameter ratio was 1.3. Procedural haemodynamics showed a decrease in peak RV to pulmonary artery gradient (mmHg) from 50 (14-86) to 11 (5-23) (P<0.001), in RV systolic pressure (mmHg) from 69 (35-110) to 40 (25-50) (P=0.006) and in RV/aortic systolic pressure ratio from 0.8 (0.4-1.0) to 0.4 (0.3-0.6) (P=0.004). Acute device-related complications occurred in four patients (36.4%): two confined conduit tears managed with placement of a covered stent; and two vascular access complications. Mean follow-up after PPVI was 3.9 years (41 days to 6.7 years). At last follow-up, one patient had undergone surgical conduit replacement for recurrent conduit stenosis, one had percutaneous pulmonary valve dilatation and two had developed bacterial endocarditis and undergone surgical conduit replacement. Freedom from valve dysfunction at 1, 2 and 3 years was 91%, 91% and 82%, respectively. CONCLUSIONS: PPVI is feasible in small conduits ≤ 16mm with good procedural and early haemodynamic results, postponing the need for surgery. These results are not sustainable over time. Larger studies are needed to determine if bare-metal stent implantation as a bridge to surgical replacement provides the same results in this specific population.

Vascular anatomy in children with univentricular hearts regarding transcatheter bidirectional Glenn anastomosis.

BACKGROUND: Transcatheter stent-secured Glenn anastomosis, aiming to reduce the invasiveness of palliation in patients with univentricular heart defects, has been reported in large experimental animals. The advent of biodegradable stents and tissue-engineered vascular grafts will make this procedure a reality in human patients. However, the relationship between the superior vena cava (SVC) and the right pulmonary artery (RPA) is different in humans. AIM: To characterise vascular anatomy in children with univentricular hearts, regarding technical aspects and device design for this procedure. METHODS: Retrospective analysis of 35 thoracic computed tomography angiograms at a mean age of 18.1±22.4 months. RESULTS: Two types of arrangement between the SVC and the RPA were identified: anatomy convenient for immediate wire passage and stent deployment between the two vessels (60%); and pattern of early RPA branching, requiring the perforation wire to traverse the intervascular space to avoid entrance into the upper RPA branch (40%). In patients with the convenient vascular arrangement, the vessels were nearly perpendicular, having immediate contact, with the posterior SVC aspect partially "wrapping" the adjacent RPA in most patients. In patients with early RPA branching, the mean shortest SVC-to-central RPA distance was 4.3±2.7mm. For the total population, the mean length of proximal SVC that allowed stent deployment without covering the brachiocephalic vein was 15.6±5.1mm. CONCLUSIONS: A trumpet-shaped covered stent in a craniocaudal orientation reaching from the SVC into the prebranching RPA seems most suitable for achieving bidirectional Glenn anastomosis percutaneously in humans. However, the short length of the proximal SVC and the presence of early RPA branching pose challenges for optimal design of the dedicated device.