Endovascular stent implantation in the pulmonary arteries of infants and children without the use of a long vascular sheath

Proof of Concept: A New Solution for Low-Profile Transcatheter Implantation of Optimus-L Stents in Small Children

BACKGROUND

There is no stent designed or approved for use in infants. We sought to obtain in vitro and in vivo data on a new concept conceived to implant Optimus-L stents at infant vessel diameters and offer a potential long term stent solution.

METHODS

Nineteen Optimus-L stents were mounted on 8 types of angioplasty balloons with diameters 6, 8, and 10 mm with the use of an injection-moulded hand crimper. We evaluated balloon-stent unit (BSU) stability before insertion and advancement through short Terumo introducers with incremental French size and possibility of side-arm contrast injections. Three types of long sheaths were tested. Stents were inflated to balloon nominal diameters and re-expanded to 18 and 23 mm. Stent recoil, foreshortening, and fracture were evaluated. In vivo implantations were performed afterward.

RESULTS

In vitro: Medtronic Evercross balloons and modified Terumo Destination sheaths were the best combination: BSUs were inserted in 6 F sheaths with possible injections (for 6 and 8 mm balloons), and 7 F sheaths without injections (for the 10 mm balloon). Retrieving BSUs inside the sheath required 1 additional F-size. Boston Scientific Sterling and Balton Lovix balloons, as well as APT Braidin L guiding sheaths showed unsatisfactory performance. Dilation up to 23 mm was possible, and stent shortening was < 24% at 18 mm and < 37% at 23 mm. Recoil was limited, and no stent fractured. In vivo: Optimus-L stents were used to treat 2 infants with aortic coarctation and 2 children with pulmonary artery stenosis with the use of 8 mm balloons and low-profile access.

CONCLUSIONS

Optimus-L stents can be implanted safely in small patients with a low-profile approach. These stents have the potential to achieve adult size while maintaining structural integrity.

Preliminary testing and evaluation of the renata minima stent, an infant stent capable of achieving adult dimensions

Objectives

This study sought to obtain in vivo data on a new stent and delivery system specifically designed for implantation in infants with the ability to be enlarged to adult dimensions.

Background

There are no endovascular stents designed for or approved for use in infants, nor is there a stent capable of being implanted at infant vessel diameters and achieving adult size while maintaining structural integrity. The Minima stent was designed to address these needs.

Methods

This study was performed in 6 piglets who underwent implantation of 22 Minima stents into the following locations: aorta (n = 11), branch pulmonary arteries (n = 6), and central veins (n = 5).

Results

Successful deployment occurred in 21/22 attempts. Two instances of post‐deployment migration occurred. Stents were re‐expanded at 1, 2, 3 and 5 months after implant. All stents regardless of location could be re‐dilated to the intended diameter to keep pace with somatic growth (implant diameter 6.9 +/− 1.2 mm; final diameter 16.1 mm +/− 1.4 mm). Histopathology at 1 and 5 months demonstrated widely patent vessel lumens with stent apposition to vessel wall, early mild inflammatory response surrounding stent struts, typical vascular damage and healing response to acute dilation and a progressive smooth neointimal growth covering stent struts over time.

Conclusions

In this in vivo study of the Minima stent, there was high implant success, predictable re‐dilatability to adult diameters and favorable histopathology. Further study is warranted.

Right ventricular outflow tract stenting in symptomatic infants without the use of a long delivery sheath

BACKGROUND AND OBJECTIVES

Right ventricular outflow tract (RVOT) stenting improves systemic oxygenation and facilitates pulmonary arterial growth in symptomatic infants prior to repair of tetralogy of Fallot. The aim of this study was to evaluate the safety and efficacy of RVOT stenting without the use of a long delivery sheath.

METHODS

Retrospective data analysis of patients under 1 year of age undergoing RVOT stenting from January 2010 to January 2020 at a single tertiary pediatric cardiology center.

RESULTS

Sixty-three RVOT stents were deployed during 53 procedures into 44 patients. The median age and weight at insertion were 41 days (range 2-204) and 3.6 kg (range 1.59-7) respectively. Thirty-one procedures were semi-elective and 22 were emergencies. Stent positioning was guided by transthoracic echocardiogram and/or RV angiography from a pigtail micro-catheter placed via the aorta. The median total procedure and fluoroscopy times were 67.5 (range 15-145) and 19 min (1-107), respectively. The median length of hospital stay was 7 days (range 1-258). Twenty-one patients were admitted to ICU post-procedure with a median ICU length of stay of 3 days (range 3-11). There were three major complications including two deaths within 30 days of the procedure. A patient with Cornelia de Lange Syndrome (1.8 kg) died following stent migration and inability to wean from emergency cardiopulmonary bypass and the second infant had an unexplained asystolic arrest post-procedure while awaiting transfer to ICU.

CONCLUSIONS

RVOT stenting is technically possible with minimal complications without the need for a long delivery sheath. Additional imaging with transthoracic echocardiography can facilitate the safe deployment of the stent.

Energy-efficient implantable transmitter for restenosis monitoring with intelligent-stents

An analog circuit forming part of an intelligent-stent system is proposed with the aim of converting pressure-related capacitance measurements into a FM signal (around 800 MHz) to be analyzed outside of the patient body. Based on the information obtained from this signal, a reliable restenosis monitoring can be carried out. An energy-saver block controls the oscillator and reduces the power consumption of the whole circuit from 547.1 μW in active state to 152.1 μW in idle state, in order to comply with energy restriction imposed by inductive coupling powering. The design is implemented in TSMC 0.18 μm CMOS technology.

Pulmonary artery stents in the recent era: Immediate and intermediate follow-up

BACKGROUND

Long-term follow-up after stent dilation of native and acquired pulmonary artery stenosis is scarce in the pediatric population. Most cohorts include a myriad of anatomies and associated conditions.

METHOD

In order to establish objective performance criteria, we performed a retrospective review of all patients who underwent unilateral pulmonary artery stenting in biventricular physiology at three centers from June 2006 to June 2011.

RESULTS

Fifty-eight patients received 60 stents with Palmaz Genesis stent used most commonly (78%). Average age at implantation was 10.4 ± 10.3 years and weight 31.6 ± 21.8 kg. The immediate success rate was 98%, with improvement in minimal diameter from 5.1 ± 2 cm to 10.6 ± 3 cm (P < 0.01). There were 10 complications (7 major and 3 minor) and no acute mortality. One-year follow-up studies were available in 48 patients (83%), including echocardiogram (60%), catheterization (28%), MRI (29%), and lung perfusion (31%). Follow-up echocardiogram showed mild increase in stent gradient, from 5.7 ± 6.7 mm Hg post-procedure to 17.1 ± 11.7 mm Hg. Follow-up catheterization showed no significant change in minimal stent diameter (8.8 ± 2.6 to 7.8 ± 2.3 mm), gradient (7.7 ± 8.4 to 12.6 ± 12.2 mm Hg), or right ventricular pressures (43.7 ± 9 to 47.7 ± 10.5 mm Hg). Nine patients (16%) underwent scheduled stent redilation over a period of 12 days to 25 months.

CONCLUSION

In conclusion, stent implantation shows excellent immediate and 1-year follow-up results with maintenance of improved caliber of the stented vessel and lowered right ventricular systolic pressures.

Catheter Interventions for Pulmonary Artery Stenosis: Matching the Intervention with the Pathology

Pulmonary artery (PA) stenosis represents a heterogeneous defect with a wide morphology and etiology. Interventions to treat PA stenosis should be based on the location, severity, and cause of stenosis as well as the size of the patient at presentation. Specialized dilation balloons, stents, and delivery techniques have been developed to treat a variety of PA stenoses in small infants through adulthood. Early and intermediate results of angioplasty and stenting are superior to surgical results, while long-term data on angioplasty and stenting are becoming available for these proven safe and effective techniques.

Medium and long-term outcomes after bilateral pulmonary artery stenting in children and adults with congenital heart disease

Percutaneous stenting of branch pulmonary arteries (PAs) has become an important interventional therapy in the complete management of congenital heart disease. Few data exist on long-term outcomes for patients requiring placement of bilateral stents. This study aimed to determine the medium- to long-term outcomes after bilateral stenting of branch PAs in patients with congenital heart disease. A retrospective study analyzed all procedural and follow-up data on patients undergoing bilateral PA stenting during a single procedure. From October 2001 to May 2012, 26 patients underwent bilateral PA stenting (total of 62 stents). The mean age of these patients was 9.5 ± 12 years, and their mean weight was 27 ± 19 kg. The mean procedural time was 191 ± 67 min, and the mean fluoroscopy time was 50 ± 29 min. The mean gradient across the right pulmonary artery decreased from 35 ± 22 to 11 ± 12 mmHg (p < 0.001). The left pulmonary artery gradient decreased from 32 ± 17 to 10 ± 12 mmHg (p < 0.001), and the right ventricle to descending aorta pressure ratio decreased from 71 ± 18 % to 46 ± 13 % (p < 0.001). Intraprocedural adverse events were encountered in four patients (1 small PA dissection, 2 intraprocedural arrhythmias, and 1 first-degree burn on the thigh). The mean follow-up period was 41 ± 23 months. Two deaths occurred. Further interventions were required for 12 patients. Bilateral PA stenting is effective and safe, with an instantaneous significant decrease in pressure gradients. The need for reintervention is common, so continued follow-up assessment is warranted.

Effect of endovascular stenting of right ventricle to pulmonary artery conduit stenosis in infants with hypoplastic left heart syndrome on stage II outcomes

There is growing awareness that the Norwood procedure with the Sano modification is prone to early right ventricular to pulmonary artery (RV-PA) conduit stenosis resulting in systemic oxygen desaturation, increased interstage morbidity, and death. We report our experience with endovascular stent placement for conduit stenosis and compare the outcomes at stage II surgery between stented and nonstented infants. The medical records of all patients with hypoplastic left heart syndrome who received an RV-PA conduit at Norwood palliation from May 2005 to January 2010 were reviewed. The preoperative anatomy, demographics, operative variables, and outcomes pertaining to the Norwood and subsequent stage II surgeries were obtained and compared between stented and nonstented infants. The pre- and post-stent oxygen saturation, stenosis location, type and number of stents implanted, concomitant interventions, procedure-related complications, and reinterventions were collected. Of the 66 infants who underwent the Norwood procedure with RV-PA conduit modification, 16 (24%) received stents. The anatomy, demographics, and outcome variables after the Norwood procedure were similar between the stented and nonstented infants. The age at catheterization was 93 ± 48 days, and the weight was 4.9 ± 1.2 kg. The oxygen saturation increased from 66 ± 9% before intervention to 82 ± 6% immediately after stenting (p <0.0001). No interstage surgical shunt revisions were performed in either group. Age, weight, pre-stage II echocardiographic variables, oxygen saturation, and operative and outcome variables, including mortality, were similar between the 2 groups. In conclusion, endovascular stent placement for RV-PA conduit stenosis after the Norwood procedure leads to improved systemic oxygen levels and prevents early performance of stage II surgery without compromising stage II outcomes.

Fontan "Ten Commandments" revisited and revised

Choussat's "Ten Commandments," which describes the components of an ideal Fontan candidate, was first published in 1977. Despite the wisdom in these commandments, it is clear from a historic perspective that total compliance with all criteria does not necessarily portend excellent long-term survival. I believe the end point of the original commandments should be modified to include improvement in long-term survival. I suggest the following single commandment: "Thou Shalt Be Perfect."

Cheatham-Platinum stent implantation for pulmonary artery stenosis in children and adolescents: immediate and mid-term outcome

BACKGROUND

NuMED Cheatham-Platinum (CP) stent implantation for pulmonary artery stenosis in children and adolescents has been rarely reported. This study aimed to evaluate the immediate and mid-term results of CP stent implantation for the treatment of pulmonary artery stenosis associated with congenital heart disease (CHD) in children and adolescents.

METHODS

From August 2005 to May 2007, four consecutive pediatric patients with pulmonary artery stenosis associated with CHD underwent CP stent implantation. They were followed up, and transthoracic echocardiography was done for outcome evaluation.

RESULTS

In the four patients, 5 stent placement procedures were performed and 7 CP stents were implanted (8-zig, 22-39 mm in length). All stents except one were successfully placed in the target lesions without displacement during the procedures. After the procedure, the systolic pressure gradient across the stenosis decreased from 36.67 ± 20.08 to 3.67 ± 3.20 mmHg (P=0.005), and the narrowest diameter of the stenotic segment increased from 6.97 ± 2.22 to 13.40 ± 4.40 mm (P=0.013). Two stents implanted in the left and right pulmonary arteries in patient 4 developed intrastent restenosis 6 months after the procedure, and the distal end of the main pulmonary artery also developed restenosis 26 months later. The results of the remaining stents have been stable without complications during a median follow-up of 34 months (range, 26-48 months).

CONCLUSIONS

Our experience indicates that CP stent implantation is suitable for the treatment of pulmonary artery stenosis in children and adolescents with CHD. The immediate and mid-term results are encouraging, but long-term results demand further follow-up in more cases.

Interventions complementing surgery as part of multistage treatment for hypoplastic left heart syndrome: one center's experience

BACKGROUND

Interventional procedures often are used as part of multistage treatment for hypoplastic left heart syndrome (HLHS). This study aimed to evaluate the efficacy of interventions in multistage treatment of HLHS.

METHODS AND RESULTS

Between 1999 and 2007, 78 interventions were performed for 58 children with HLHS at different stages of surgical treatment. Group 1, involving 30 interventions for 22 patients with postoperative pulmonary arterial stenosis, showed reduced pulmonary artery pressure and increased vessel diameter. Group 2, involving 15 interventions after the Norwood operation for 12 patients with aortic arch obstruction, showed success for 11 patients. Group 3, involving eight balloon angioplasties of narrowed Glenn anastomosis for seven patients, showed abolition of the pressure gradient between the superior vena cava and the right pulmonary artery. Group 4, involving eight interventional closures of a fenestration for eight patients after a Fontan operation, showed increased oxygen saturation for all eight patients. Group 5, involving seven interventions for six patients in whom venovenous collaterals were closed percutaneously, showed improved oxygen saturation. For Group 6, uncommon miscellaneous interventions were used to stabilize the patients' condition before the next surgical treatment.

CONCLUSIONS

Interventional procedures play an important role during multistage treatment of HLHS. They allow for a reduction in the number of operations or stabilization of the patients' condition before the next surgical treatment.

Genesis stent implantation without using a long sheath in two children

A Genesis stent was implanted in two children, one with superior vena caval (SVC) stenosis and one with pulmonary artery branch stenosis. Case 1 was a 2-month-old baby with SVC stenosis following intracardiac repair for total anomalous pulmonary venous connection (TAPVC) and case 2 was a 2-year-old child with left lower pulmonary artery stenosis following one-stage unifocalization for dextrocardia, double outlet right ventricle, ventricular septal defect, pulmonary atresia and major aortopulmonary collateral arteries. Both procedures resulted in immediate clinical and hemodynamic improvement. The Genesis stent has a closed-cell design with sigma hinges interpositioned between each cell. With improved deliverability and expandability of the stent, we can easily deliver it through smaller sheaths, which will facilitate its use in infants and smaller children with vascular stenosis.

Peripheral pulmonary artery stenosis in a four-month-old West Highland White Terrier

A 4-month-old West Highland White Terrier was evaluated for dyspnea. Severe cardiac silhouette enlargement was present radiographically. Severe right ventricular hypertrophy and dilation with a dilated pulmonary trunk and a stenosis of the right pulmonary artery were diagnosed via echocardiography. Additional areas of peripheral pulmonary artery stenosis were diagnosed with nonselective computed tomography (CT) angiography and selective fluoroscopic angiography. Balloon dilation therapy was unsuccessful and the imaging findings were confirmed at necropsy.

Tratamento endovascular de pseudo-aneurisma da artéria subclávia em criança hemofílica

O uso de cateteres venosos centrais em pacientes hemofílicos é muito freqüente, devido às próprias características terapêuticas da doença. As complicações desses procedimentos, tais como pseudo-aneurisma, geralmente são mais graves nesses pacientes. A correção cirúrgica do pseudo-aneurisma que acomete a artéria subclávia constitui um dos maiores desafios da cirurgia vascular. Em pacientes hemofílicos, à dificuldade habitual de exposição cirúrgica somam-se os problemas de alteração no processo normal de coagulação. Como alternativa ao tratamento cirúrgico convencional, a utilização de técnicas endovasculares constitui uma solução segura e com bons resultados.

Successful dilatation of left pulmonary artery stenosis by stent implantation through a modified Blalock-Taussig shunt in an infant with pulmonary atresia and ventricular septal defect

We successfully implanted a coronary stent via a modified Blalock-Taussig shunt to relieve stenosis of the left pulmonary artery in an infant with pulmonary atresia and ventricular septal defect. The placement of a flexible coronary stent via a modified Blalock-Taussig shunt is a safe and feasible catheter intervention for the treatment of infants with hypoplastic pulmonary arteries.

Bare delivery of medium and large stents in patients with congenital heart disease

The medium and large stents favored by pediatric cardiologists are typically delivered through a long sheath placed distal to the target lesion. However, long sheath placement can be problematic. The aim of the study was to determine whether stents can be safely delivered without using a long sheath in patients with congenital heart disease. Between July 2001 and October 2002, primary bare stent delivery was attempted in 17 consecutive patients with 21 target lesions. All 21 stents were successfully delivered without employing a long sheath. The series demonstrates that medium and large stents can be safely delivered without a long sheath in patients with congenital heart disease. Furthermore, eliminating the long sheath can improve stent delivery and allow new options when addressing bifurcation lesions.

The Genesis stent: A new low-profile stent for use in infants, children, and adults with congenital heart disease

Placement of intravascular stents that can reach adult size in infants and smaller children has been limited by the large profile and poor flexibility of currently available stents. In vitro and in vivo testing of the Genesis stent was performed to evaluate crimpability, predeployment flexibility, and radial strength. Comparisons were made to the Palmaz iliac and IntraStent (IS) LD stents. Nine physicians placed 30 Genesis stents in swine pulmonary and systemic arteries to evaluate stent deliverability/crimpability. Two swine were recovered and underwent a second catheterization 8 weeks later, where the stents (n = 8) were reexpanded to maximal size. Angiographic and intravascular ultrasound (IVUS) assessments were performed. In vitro testing revealed the Genesis stent to have superior crimpability, flexibility, and comparable radial strength to the Palmaz iliac stent, and superior crimpability and radial strength and comparable flexibility to the IS LD series. During in vivo testing, the physicians graded the Genesis stent superior to the Palmaz stent regarding crimpability and deliverability, and superior to the IS LD stent in regard to crimpability, and comparable to or superior in deliverability. In the chronic animals, the Genesis stent was expanded up to maximal diameter 8 weeks following implantation. Angiographic and IVUS revealed no fractures no in-stent restenosis. The Genesis stent can be easily delivered through smaller sheaths, which will facilitate their use in infants and smaller children with vascular stenosis.