Simultaneous Stent Implantation for Pulmonary Artery Bifurcation Stenosis in Infants

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J INVASIVE CARDIOL 2024. doi:10.25270/jic/24.00097. Epub May 15, 2024.

Objectives. Pulmonary artery (PA) bifurcation stenosis often requires simultaneous stent placement, which may be technically challenging. Limited data exist regarding this practice in infants. We aim to report the procedural outcomes and safety of bifurcation stent placement in infants.

Methods. We performed a single-center retrospective review of infants younger than 12 months who underwent simultaneous stent placement for PA bifurcation stenosis from January 1, 2001 through December 31, 2019.

Results. Seventeen infants underwent simultaneous PA bifurcation stent placement. The median age was 6.4 months (1.1-10.1 months), and weight was 5.8 kg (3-10.6 kg). Nine (52.9%) patients had had prior PA intervention. Most stents were placed in central PAs (28, 82.4%), followed by lobar branches (6, 17.6%). All patients received pre-mounted stents. The peak gradient across each branch decreased from 47.4 ± 16 to 18.7 ± 13 mm Hg (P < .0001). The right ventricle to systemic systolic pressure ratio decreased from systemic (1.0 ± 0.3) to just over half systemic (0.58 ± 0.2) (P = .0001). The minimum vessel diameter increased from 3.6 ± 1.5 to 6.0 ± 1.9 mm (P < .0001). There were 4 (23.5%) patients with high severity adverse events. There were no procedure-related deaths. The median follow-up period was 83.8 months (5.3 months-19.4 years). All patients had subsequent PA re-intervention at a median time of 8.1 months (2.9 months-8.8 years), and median time to re-operation was 19.1 months (2.9 months-7.5 years).

Conclusions. Simultaneous PA stent placement is an effective strategy for relief of bifurcation stenosis in infants. Future transcatheter interventions are necessary to account for patient growth, but may delay the need for re-operation.

Pulmonary artery (PA) stenosis may occur in isolation but is more commonly associated with other forms of congenital heart disease in children. Stent placement is an established treatment option for addressing PA stenosis in children¹ and is highly successful in increasing PA size, reducing gradients, and decreasing right ventricular (RV) systolic pressure.^2,3 Stent placement requires re-intervention to match somatic growth in pediatric patients.^4,5 Small stents can be implanted in infants and small children as a palliative strategy by allowing for future balloon dilation and surgical removal at a later operation.^1,6

Pulmonary artery bifurcation stenosis can occur in patients with congenital heart disease, typically after cardiac surgery. Bifurcation stenosis may be technically challenging to address given the risk of “jailing” the contralateral branch with stent placement. There are several proposed transcatheter treatment options to address bifurcation stenosis.^7-9 Simultaneous “kissing” PA stent implantation was first described in 2001 by McMahon et al.,¹⁰ and 1 series has been published on its long-term outcomes in a cohort of pediatric and adult patients. This series showed immediate relief of bifurcation stenosis and potential for further dilation, but there was a high rate of re-intervention due to patient growth and in-stent stenosis.⁸ Other techniques to address PA bifurcation stenosis include implanting a single stent mounted on 2 balloon catheters across both areas of stenosis⁷ and a Y-stenting technique, where a stent is placed across 1 area and a second stent is then placed through side cells into the contralateral branch.^9,11

Limited data exist on simultaneous PA stent placement in infants and their long-term outcomes. Our study aimed to report the procedural outcomes and safety of bifurcation stent placement in infants, particularly the long-term trajectory of re-interventions.

We conducted a retrospective review of infants under 12 months of age who underwent simultaneous stent placement for PA bifurcation stenosis at our institution from January 1, 2001 through December 31, 2019. Patients were identified retrospectively via our cardiac catheterization clinical database. We included infants who had stents placed in either proximal or lobar PAs. We excluded patients who were older than 12 months at initial stent placement or who underwent unilateral or non-simultaneous PA stent placement.

The technique for simultaneous stent placement has been described previously.^8,10 In summary, 2 venous sheaths are placed, and hemodynamics and angiography are completed. Both areas of stenosis are crossed with catheters, then exchanged for stiff wires. Two appropriately sized stents are positioned across the stenotic areas from each venous sheath, then balloons are simultaneously inflated to deploy the stents. Alternatively, 1 stent is deployed initially, followed by simultaneous balloon inflation when the contralateral stent is placed. In both techniques, both balloons are simultaneously deflated in order to prevent deformation of the contralateral stent (Figure 1). Stents are further simultaneously balloon-dilated as needed. In cases where small-sized coronary stents are used, both stents may be placed through a single venous sheath.

Medical records, catheterization data, and operative reports were reviewed for demographic data, cardiac and non-cardiac diagnoses, and prior procedural data. Imaging reports from echocardiograms, lung perfusion scans, computed tomography, and magnetic resonance imaging studies were reviewed. Angiograms were reviewed retrospectively, and vessel measurements were performed using CAAS Workstation software (Pie Medical Imaging).

The recorded catheterization data included age, weight, body surface area, procedural indications, vascular access, hemodynamic data, interventional details, and procedural complications. Specific details on stent and balloon size and type were collected. Hemodynamic data included right ventricle to systemic systolic pressure ratio and pressure gradients prior to and after stent placement. Using adverse event classification from the Congenital Cardiac Catheterization Outcomes Project (C3PO),^12,13 high severity adverse events (HSAE) included moderate, major, and catastrophic severity categories (Level 3, 4, 5). Examples of HSAE are stroke, death, and events that may be life-threatening requiring intervention, cardiopulmonary resuscitation, surgery, or repeat catheterization. Lower severity or minor adverse events were transient with no long-term sequelae.

Outcome measures were change in hemodynamic values after bifurcation stent placement, need for and type of re-intervention, procedural complications, and patient death. Follow-up data consisted of follow-up length and details of subsequent surgeries and catheterizations.

Statistical analysis was performed using Stata software, version 16.1 (StataCorp). Data were reported as frequencies and percentages, median and range, or mean and standard deviation, as appropriate. Comparative data analysis of pre- and post-intervention hemodynamic data was performed using paired student’s t-test, and analysis of echocardiography data was performed using Wilcoxon signed rank test. Statistical significance was set at a P-value of less than .05. This study was approved by the Columbia University Medical Center’s Institutional Review Board. Informed consent was obtained by the patient’s guardian(s) prior to each catheterization.

Patient characteristics. Sixty-eight patients were identified who underwent simultaneous PA bifurcation stent placement at our institution from January 1, 2001 through December 31, 2019. We excluded 51 patients based on the criteria described earlier. A total of 17 patients (11 male, 6 female) were included in this study. Three (25%) patients were premature, 7 (41.2%) patients had diagnosed genetic disorders, and no patients had single ventricle physiology. Associated cardiac diagnoses are outlined in Table 1. All 17 patients underwent initial cardiac procedures at a median of 2.1 months (range: 1 day-8 months) prior to bifurcation stent placement, including 20 surgeries and 5 transcatheter interventions.

Initial catheterization. Patient characteristics at the time of initial catheterization are outlined in Table 2. Median age at bifurcation stent placement was 6.4 months (range: 1.1-10.1 months) with a median weight of 5.8 kg (range: 3-10.6 kg). A total of 34 stents were placed (17 pairs). Twenty-eight (82.4%) stents were placed in the central PAs and 6 (17.6%) were placed in lobar branches. The majority of cases (15/16, 93.8%) required 2 venous access sites except in the case of placement of coronary stents, where 1 venous access site was used. All patients received pre-mounted stents; in 2 cases (11.8%), coronary stents were used. The most common stent used was pre-mounted Genesis (Cordis) (20, 58.8%) followed by Palmaz Blue (Cordis) (10, 29.4%) and Multi Link Vision coronary stents (Abbott) (4, 11.8%). Stent size ranged from 2.5 mm to 8 mm in diameter (median: 6 mm). Three patients (17.7%) underwent additional stent placement during the same procedure, including within contralateral lobar branches and inferior vena cava secondary to stent migration.

Two patients required mechanical circulatory support around the time of initial bifurcation stent catheterization. One patient was on mechanical circulatory support prior to stent placement due to inability to wean from cardiopulmonary bypass after major aortopulmonary collateral artery unifocalization. Another patient was placed on emergency support in the setting of cardiac arrest several days post-stent placement. 

Following stent placement, the peak gradient across each stented branch decreased from 47.4 ± 16 to 18.7 ± 13 mm Hg (P < .0001). Minimum vessel diameter increased from 3.6 ± 1.5 to 6.0 ± 1.9 mm (P < .0001). Right ventricle to systemic systolic pressure ratio decreased from systemic (1.0 ± 0.3) to just over half systemic (0.58 ± 0.2) (P = .0001) (Table 3).

Echocardiography. Right ventricular function improved significantly after initial bifurcation stent placement by qualitative echocardiographic evaluation. Prior to catheterization, 5 patients (33.3%) had qualitatively normal RV function, which increased to 8 patients (57.1%) post-procedure (P = .04) (Table 4).

Complications. Of the 17 total procedures, there were 5 HSAE in 4 patients (23.5%), including hypotension and bradycardia requiring treatment in 3 cases and stent embolization in 2. Three cases of hypotension and bradycardia were treated with inotropic support (epinephrine, dobutamine) and 1 patient also required a brief period of chest compressions. Stent embolization occurred in 2 cases; 1 patient was noted to have distal migration of the stents 1 to 2 days post-placement, and the second patient had immediate embolization of the stent during balloon inflation and the stent was subsequently placed in the inferior vena cava. There were 3 patients (17.7%) with minor complications, including 2 cases related to vascular access and 1 with post-procedure respiratory insufficiency requiring further observation. There were no procedure-related deaths in our cohort (Table 2).

Repeat catheterization. Twelve patients (70.6%) underwent repeat catheterization within the follow-up period after bifurcation stent placement. Five patients (29.4%) required 3 catheterizations, and 1 patient (5.9%) required 4. The median age at repeat catheterization was 12.6 months (range: 4.7 months-9.5 years). From initial stent placement to repeat catheterization, the average peak gradient across each stented branch increased from 16 ± 10.3 to 53 ± 32.9 mm Hg (P < .0001). The minimum vessel diameter decreased from 6.3 ± 2.1 mm to 4.3 ± 1.9 mm (P < .0001). The right ventricle to systemic systolic pressure ratio increased from 0.6 ± 0.25 to 1.0 ± 0.49 (P = .0017) (Table 3). No patient required mechanical circulatory support at the time of repeat catheterizations. There was 1 HSAE with hypotension and bradycardia requiring medical treatment, and no patient deaths.

Follow-up. Follow-up data are outlined in Table 5. Of the 17 patients who underwent PA bifurcation stent placement, the median follow-up period was 83.8 months (range: 5.3 months-19.4 years). All patients had subsequent PA re-interventions: 4 transcatheter only, 7 transcatheter followed by later surgery, 5 surgeries for another primary indication, and 1 surgery followed by later transcatheter intervention (Figure 2). Indications for re-intervention included right ventricular hypertension, decreased right ventricular function, in-stent stenosis, or quantitative flow discrepancy.

Each patient required a median of 1 additional PA intervention after stent placement (range: 1-6). The median time to the first PA re-intervention of any type (surgery or transcatheter) was 8.1 months (range: 2.9 months-8.8 years). The time to a transcatheter re-intervention was 8.4 months (range: 3.5 months-8.8 years; n = 12), and the time to surgery was 19.1 months (range: 2.9 months-7.5 years; n = 13) after initial bifurcation stent placement. When the cohort was separated by age at bifurcation stent placement, time to re-intervention was shorter in patients under 6 months old, but this was not statistically significant. (P = .05) (Figure 3).

There was a total of 33 PA re-interventions in our cohort with 18 transcatheter interventions (54.5%) and 15 surgeries (45.5%). Cardiac surgeries included right ventricle to pulmonary artery (RV-PA) conduit revision in 10 cases, right ventricle outflow tract augmentation in 3, PA stent removal and/or plasty in 15, pulmonary valve replacement in 2, and other cardiac repairs in 4. In 12 cases, PA stent removal ± PA plasty was performed at the time of concomitant surgical repair. Catheterizations included balloon dilation of bifurcation stents in 8 cases, placement of a second set of bifurcation stents in 6, stent placement in areas other than at bifurcation stenosis in 4, and RV-PA conduit stenting in 1 case.

This study investigated the procedural outcomes and safety of simultaneous PA bifurcation stents in infants at a large single center over a 19-year period. In a cohort of 17 patients, simultaneous stent placement showed acute procedural success in increasing minimal vessel diameter and reducing pressure gradients across bifurcation stenosis with no procedure-related deaths. All patients required further surgical and/or transcatheter PA interventions. This is the first reported case series of simultaneous PA bifurcation stents in an infant cohort.

PA stenting is an established treatment in addressing postoperative, congenital, and extrinsic compression stenosis.¹ In pediatrics, stent placement requires re-intervention to match somatic growth.^4,10 Small stents can be used in infants and small children despite the inability to achieve adult size as a palliative strategy to delay the need for surgical repair.^1,6 These smaller stents can be successfully balloon-dilated or surgically removed at a later operation,⁶ which was seen in our cohort. Intentional transcatheter stent fracture has been described as an approach to dilating existing stents to match somatic growth, although the underlying stent substrate and method of balloon dilation are key considerations in the overall success of this approach.¹⁴

Simultaneous stent placement to treat bifurcation stenosis in coronary and renal arteries has been well described.^15-17 Besides simultaneous bifurcation stents, there are few transcatheter treatment options for PA bifurcation stenosis. Previous studies described the use of a single stent mounted on 2 balloon catheters⁷ and a Y-stenting technique, where a stent is placed in the main PA extending into either branch PA, followed by second stent placement through the side cells of the initial stent.^9,11 Y-stenting has the advantage of utilizing a single sheath approach compared with most simultaneous stent cases, which may be beneficial in infants and small children. Another potential disadvantage of simultaneous bifurcation stents is that it results in a double lumen proximal PA, which may be difficult to enter at future transcatheter interventions.⁹ This may also account for high rates of in-stent stenosis (32%) and can increase the need for re-intervention (68%). Possible explanations include increased turbulent flow at areas of bifurcation and more exposed stent surface at the double layer of stent material.⁸ In our series, re-intervention was inevitable owing to patient size and initial stent size and type. However, surgical stent removal and further transcatheter interventions occurred successfully without major issues with accessing bifurcation stents.

Our initial catheterization data show that simultaneous bifurcation stenting provides effective relief of pressure gradients, increases vessel lumen diameter, and reduces right ventricle systolic pressure while improving the echocardiographic assessment of right ventricle function. This is consistent with prior reports of this technique.^8,18 Our follow-up data suggest that the use of PA bifurcation stents was able to successfully delay time to surgery from 8 to 19 months, which may alleviate operative risks related to patient age and size. There was no significant difference in time to re-intervention based on age at initial stent placement; however, patients who were younger at stent placement returned to the cath lab or operating room earlier than older patients.

We found a high and low severity complication rate of 23.5% and 17.7%, respectively, with no procedural deaths. Our complication rates are higher than previously published literature on PA stent placement in children, ranging from 12% to 17%.^2,3,19 The prior series on bifurcation stents reported 6.2% major and 16.3% minor complications.⁸ Age and size differences in these studies may account for this variation, as none of the prior studies focused on infants under 1 year of age, and younger age and weight are known factors associated with higher rates of adverse events.²⁰ 

Simultaneous bifurcation stent implantation typically requires multiple venous access sites and arterial access for hemodynamic monitoring. This may lead to increased vascular complications in infants and small children.^21-24 In our series, 2 patients had loss of arterial pulses, which was not directly related to the bifurcation stent insertion. None of our patients were diagnosed with venous thrombosis. Infants with congenital heart disease who undergo multiple catheterizations are at risk for vascular compromise. Utilizing multiple access sites may increase the cumulative odds of complications; however, this risk should be weighed against potential morbidity related to operative intervention and repeated cardiac surgeries.²⁵

As anticipated, all patients required PA re-intervention. Only pre-mounted stents with maximal diameters that do not reach adult size were placed in our patients. Transcatheter re-interventions on bifurcation stents were performed successfully with balloon angioplasty of existing stents or placement of new stents within previous pairs with only 1 HSAE. Seven patients were able to be further palliated by transcatheter re-intervention before eventually returning to the operating room, effectively delaying time to surgery and potentially reducing operative risks. Notably, all surgeries performed after stent placement were for primary indications other than to address bifurcation stenosis. Most frequently, RV-PA conduit replacement was performed in addition to stent removal and PA plasty.

Limitations. This study is limited by its retrospective, single-center design with a limited number of patients due to the infrequent nature of PA bifurcation stenosis in infants. The use of lung perfusion scans and cross-sectional imaging was not uniform within our cohort, although future studies may utilize this data to assess regional lung perfusion, quantitative flow metrics, and right ventricle volume and function. Lastly, clinical decision-making and choice of stents were dependent on the operator. Future studies should include multiple centers to increase the study population and should focus on procedure-specific outcomes such as angiographic relief of stenoses and methods to reduce adverse events.

Simultaneous PA bifurcation stent placement is an effective treatment for relief of bifurcation stenosis in an infant population. Bifurcation stents may delay the need for surgical intervention in this high-risk population, and all patients require further PA re-intervention owing to patient size and growth. Complication rates at initial stent placement are high, but future interventions can be performed successfully with repeat catheterization or surgery.

From the Division of Pediatric Cardiology, Department of Pediatrics, Columbia University Irving Medical Center, Morgan Stanley Children's Hospital, New York, NY, USA.

Disclosures: The authors report no financial relationships or conflicts of interest regarding the content herein.

Address for correspondence: Mariel E. Turner, MD, Division of Pediatric Cardiology, Columbia University Irving Medical Center, 3959 Broadway- 2N, New York, NY 10032, USA. Email: met2148@cumc.columbia.edu