EXPLANATION


Pulmonary flow restriction via a transcatheter placed modified microvascular plug (MVP) [Medtronic, Minneapolis, MN] is a novel, percutaneous approach to control pulmonary blood flow (PBF) compared with pulmonary artery banding (PAB) via sternotomy. A swine model, published in 2018, demonstrated the feasibility of modified MVPs as retrievable pulmonary flow restrictors (PFR).¹ Previous attempts at percutaneous PFR with other devices were plagued with concerns regarding large delivery systems, unpredictable PBF, and uncertainty regarding removal. The current MVP device is only FDA-approved for peripheral vascular embolization but has been used “off label” for PDA closure. It is available in four sizes, delivered through a microcatheter, is re-sheathable, and has reliability in predicting PBF.


Retrospective, single center studies have shown the feasibility of utilizing modified MVPs as PFRs to stabilize high-risk neonates with pulmonary overcirculation and defer surgery for weeks to months.^2,3 The most common complication seen in these initial studies is device embolization. Other complications include device thrombosis, device rupture, persistent overcirculation, and access site complications.


A 2023 article describes Boston Children’s Hospital’s experience with MVP PFRs.² A total of 17 high-risk neonates, predominantly with hypoplastic left heart syndrome (HLHS), underwent placement of modified MVPs instead of hybrid stage 1 with sternotomy and PAB placement. Throughout the reported 2-year experience, many modifications were made in device fenestration technique and location of device placement. Over 40% required concomitant procedures including PDA stenting or enlargement of atrial communication. One third of the patients experienced device embolization/migration with many embolization events occurring after procedure completion and without acute symptoms. Two patients (5%) developed device thrombosis. Compared with a historic cohort of high-risk neonates undergoing hybrid procedure, the 6-month all-cause mortality risk was significantly lower in the PFR group.²


A 2024 article describes the experience at Children’s Memorial Hermann Hospital with MVP PFRs.³ A total of seven neonates with HLHS or Shone’s complex with contraindications to immediate surgical stage 1 palliation, most commonly prematurity or low birth weight, underwent placement of PFRs in the bilateral branch pulmonary arteries. None of the procedures had acute complications, with no device embolization events in this cohort. One patient, with larger pulmonary arteries ultimately required sternotomy with PAB placement 5 days after PFR placement for persistent overcirculation. All devices were removed at the time of surgery with no need for pulmonary artery augmentation. One patient with MVPs in for 67 days had a challenging and protracted device removal.³


To conclude, pulmonary flow restriction with modified MVP devices exists as one potential option for controlling PBF in congenital heart disease. The patient numbers in the published series remain small, but it remains a potential avenue forward for some of the most high-risk patients.


Device embolization/migration is currently the most common complication described in the literature compared to device thrombosis or pulmonary artery stenosis.


REFERENCES


1. Khan AH, Hoskoppal D, Kumar TKS, et al. Utility of the Medtronic microvascular plug as a transcatheter implantable and explantable pulmonary artery flow restrictor in a swine model. Catheter Cardiovasc Interv. 2019 Jun 1;93(7):1320-8.


2. Sperotto F, Lang N, Nathan M, et al. Transcatheter Palliation with pulmonary flow restrictors in neonates with congenital heart disease: feasibility, outcomes, and comparison with a historical hybrid stage 1 cohort. Circ Cardiovasc Interv. 2023 Dec;16(12):e013383.


3. Warren M, Choy AV, Khan M, et al. Percutaneous pulmonary flow restriction in infants with congenital heart disease. JACC Adv. 2024 Jun 7;3(7):101031.