Comparison of conventional and cutting balloon angioplasty for congenital and postoperative pulmonary vein stenosis in infants and young children

Interventions for Pulmonary Vein Stenosis

Pulmonary vein stenosis (PVS) is a rare and unique disease of infants and young children. PVS is attended by high morbidity and mortality, and for many decades, effective therapy eluded the practitioner. However, in the most recent era, interventional techniques when employed in combination with systemic (primary) therapy have had a remarkable impact on outcomes in these at-risk children. Despite apparent complete relief of PVS in a discrete region of a pulmonary vein, stenosis reliably recurs and progresses. In this review, we discuss the current state-of-the-art interventional techniques, through the lens of our collective experiences and practices.

Targeted Rapamycin Delivery via Magnetic Nanoparticles to Address Stenosis in a 3D Bioprinted in Vitro Model of Pulmonary Veins

Vascular cell overgrowth and lumen size reduction in pulmonary vein stenosis (PVS) can result in elevated PV pressure, pulmonary hypertension, cardiac failure, and death. Administration of chemotherapies such as rapamycin have shown promise by inhibiting the vascular cell proliferation; yet clinical success is limited due to complications such as restenosis and off-target effects. The lack of in vitro models to recapitulate the complex pathophysiology of PVS has hindered the identification of disease mechanisms and therapies. This study integrated 3D bioprinting, functional nanoparticles, and perfusion bioreactors to develop a novel in vitro model of PVS. Bioprinted bifurcated PV constructs are seeded with endothelial cells (ECs) and perfused, demonstrating the formation of a uniform and viable endothelium. Computational modeling identified the bifurcation point at high risk of EC overgrowth. Application of an external magnetic field enabled targeting of the rapamycin-loaded superparamagnetic iron oxide nanoparticles at the bifurcation site, leading to a significant reduction in EC proliferation with no adverse side effects. These results establish a 3D bioprinted in vitro model to study PV homeostasis and diseases, offering the potential for increased throughput, tunability, and patient specificity, to test new or more effective therapies for PVS and other vascular diseases.

Pulmonary Vein Stenosis in Children: A Programmatic Approach Employing Primary and Anatomic Therapy

Pulmonary vein stenosis (PVS) is a difficult condition to treat due to recurrence and progression. In 2017, we developed a comprehensive PVS Program at our center to address the multidisciplinary needs of these patients. We discuss the components of our program and our approach to these patients, using a combination of primary (medical) therapy in addition to anatomic therapy to preserve vessel patency. A multidisciplinary approach to treating these challenging patients is critical.

Outcomes in Establishing Individual Vessel Patency for Pediatric Pulmonary Vein Stenosis

The purpose of this study was to determine what patient and pulmonary vein characteristics at the diagnosis of intraluminal pulmonary vein stenosis (PVS) are predictive of individual vein outcomes. A retrospective, single-center, cohort sub-analysis of individual pulmonary veins of patients enrolled in the clinical trial NCT00891527 using imatinib mesylate +/− bevacizumab as adjunct therapy for the treatment of multi-vessel pediatric PVS between March 2009 and December 2014 was performed. The 72-week outcomes of the individual veins are reported. Among the 48 enrolled patients, 46 patients and 182 pulmonary veins were included in the study. Multivariable analysis demonstrated that patients with veins without distal disease at baseline (odds ratio, OR 3.69, 95% confidence interval, CI [1.52, 8.94], p = 0.004), location other than left upper vein (OR 2.58, 95% CI [1.07, 6.19], p = 0.034), or veins in patients ≥ 1 y/o (OR 5.59, 95% CI [1.81, 17.3], p = 0.003) were at higher odds of having minimal disease at the end of the study. Veins in patients who received a higher percentage of eligible drug doses required fewer reinterventions (IRR 0.76, 95% CI [0.68, 0.85], p < 0.001). The success of a multi-modal treatment approach to aggressive PVS depends on the vein location, disease severity, and drug dose intensity.

Correlation of Intravascular Ultrasound with Histology in Pediatric Pulmonary Vein Stenosis

Preliminary intravascular ultrasound (IVUS) images of suspected pediatric intraluminal pulmonary vein stenosis (PVS) demonstrate wall thickening. It is unclear how the IVUS-delineated constituents of wall thickening correlate with the histology. We analyzed six postmortem formalin-fixed heart/lung specimens and four live patients with PVS as well as control pulmonary veins using IVUS and light microscopic examination. In PVS veins, IVUS demonstrated wall thickening with up to two layers of variable echogenicity, often with indistinct borders. Histologically, the veins showed fibroblastic proliferation with areas rich in myxoid matrix as well as areas with abundant collagen and elastic fibers. Discrete vein layers were obscured by scarring and elastic degeneration. A lower reflective periluminal layer by IVUS corresponded with hyperplasia of myofibroblast-like cells in abundant myxoid matrix. The hyper-reflective layer by IVUS extended to the outer edge of the vessel and corresponded to a less myxoid area with more collagen, smooth muscle and elastic fibers. The outer less reflective edge of the IVUS image correlated with a gradual transition into adventitia. Normal veins had a thin wall, correlating with histologically normal cellular and extracellular components, without intimal proliferation. IVUS may provide further understanding of the anatomy and mechanisms of pediatric pulmonary vein obstruction.

The many faces and outcomes of pulmonary vein stenosis in early childhood

Pulmonary vein stenosis is a rare and poorly understood condition causing obstruction of the large pulmonary veins and of blood flow from the lungs to the left atrium. This results in elevated pulmonary venous pressure and pulmonary edema, pulmonary hypertension, potentially cardiac failure, and death. Clinical signs of the disease include failure to thrive, increasingly severe dyspnea, hemoptysis, respiratory difficulty, recurrent respiratory tract infections/pneumonia, cyanosis, and subcostal retractions. On chest radiograph, the most frequent finding is increased interstitial, ground-glass and/or reticular opacity. Transthoracic echocardiography with pulsed Doppler delineates the stenosis, magnetic resonance imaging and multislice computerized tomography are used for further evaluation. Interventional cardiac catherization, surgical techniques, and medical therapies have been used with varying success as treatment options.

Preliminary findings on the use of intravascular ultrasound in the assessment of pediatric pulmonary vein stenosis

OBJECTIVE

Determine the feasibility of performing intravascular ultrasound (IVUS) in pediatric pulmonary vein stenosis (PVS) and investigate whether IVUS can delineate the mechanism of PVS.

BACKGROUND

The use of IVUS in pediatric patients with PVS has not been reported.

METHODS

Retrospective, single center, cohort analysis of all patients who underwent IVUS of pulmonary veins from August 2016 to December 2019.

RESULTS

IVUS was performed on 81 pulmonary veins in 50 pediatric patients (median age = 1.7 years [0.9, 3.1], median weight = 8.6 kg [7.3, 11.8]). All veins accepted the IVUS catheter (.014 or .018), with adequate visualization in 88% (71/81) of imaged veins, and improvement in visualization in the more recent period (23/24; 96%). Veins were categorized as having presumed intimal thickening (PIT) with luminal narrowing (n = 36), ostial narrowing without PIT (n = 14), distortion/compression (n = 6), normal (n = 2), and stent with (n = 9) or without in-stent stenosis (n = 4). In veins with at least 6 months of follow up, (re)intervention occurred more commonly in veins with PIT (14/19; 74%) versus veins without PIT (3/13; 23%; p = 0.01). There were no IVUS related adverse events.

CONCLUSION

IVUS can be used safely in pediatric patients and can reliably demonstrate vein lumen and wall architecture. With further refinement, IVUS has the potential to differentiate intimal neo-proliferation from other mechanisms of obstruction. The exact role of IVUS in the assessment of pediatric PVS is yet to be determined.

Systemic Sirolimus to Prevent In-Stent Stenosis in Pediatric Pulmonary Vein Stenosis

Evaluate the efficacy of systemic sirolimus (rapamycin) in preventing in-stent stenosis (ISS) in pediatric intraluminal pulmonary vein stenosis (PVS). Report the adverse events related to sirolimus therapy. There is a high incidence of ISS following stent implantation in PVS. The use of sirolimus in preventing ISS has not been reported. Retrospective review of all patients who received sirolimus (8 week course) for treatment of ISS for PVS between January 2013 and June 2018. Forty stents (37 bare metal, 3 drug-eluting) in 20 patients were treated with sirolimus; 20 at the time of implantation (primary prevention [1P]) and 20 following documented ISS requiring transcatheter reintervention (secondary prevention [2P]). Treated patients were young (median 2 y/o [0.7-5.7]) and most had PVS associated with congenital heart disease (75%, 15/20; 4/15 with TAPVC). In the 1P group, 85% (17/20) of stents were without significant (< 50%) ISS at median of 102 days (range 56-527); the growth rate of ISS in this group was 7.5 ± 7.1%/month. In the 2P group, most stents had a slower growth rate of ISS after sirolimus therapy compared to pre-treatment (median 3.7 [- 0.2 to 13.1] vs. 10.4 [1.3 to 19.5] %/month; p < 0.001). One patient developed pneumonia on drug while concurrently taking another immunosuppressive agent. No other serious adverse events were related to sirolimus therapy. Systemic sirolimus slows the growth rate of ISS following stent implantation in PVS compared to pre-treatment rates and was administered safely in a small number of pediatric patients with complex heart disease.

Pulmonary vein stenosis in patients with Smith-Lemli-Opitz syndrome

OBJECTIVE

To describe a group of children with co-incident pulmonary vein stenosis and Smith-Lemli-Opitz syndrome and to generate hypotheses as to the shared pathogenesis of these disorders.

DESIGN

Retrospective case series.

PATIENTS

Five subjects in a pulmonary vein stenosis cohort of 170 subjects were diagnosed with Smith-Lemli-Opitz syndrome soon after birth.

RESULTS

All five cases were diagnosed with Smith-Lemli-Opitz syndrome within 6 weeks of life, with no family history of either disorder. All cases had pathologically elevated 7-dehydrocholesterol levels and two of the five cases had previously reported pathogenic 7-dehydrocholesterol reductase mutations. Smith-Lemli-Opitz syndrome severity scores ranged from mild to classical (2-7). Gestational age at birth ranged from 35 to 39 weeks. Four of the cases were male by karyotype. Pulmonary vein stenosis was diagnosed in all cases within 2 months of life, earlier than most published cohorts. All cases progressed to bilateral disease and three cases developed atresia of at least one vein. Despite catheter and surgical interventions, all subjects' pulmonary vein stenosis rapidly recurred and progressed. Three of the subjects died, at 2 months, 3 months, and 11 months. Survival at 16 months after diagnosis was 43%.

CONCLUSIONS

Patients with pulmonary vein stenosis who have a suggestive syndromic presentation should be screened for Smith-Lemli-Opitz syndrome with easily obtainable serum sterol tests. Echocardiograms should be obtained in all newly diagnosed patients with Smith-Lemli-Opitz syndrome, with a low threshold for repeating the study if new respiratory symptoms of uncertain etiology arise. Further studies into the pathophysiology of pulmonary vein stenosis should consider the role of cholesterol-based signaling pathways in the promotion of intimal proliferation.