A flow restrictor implanted percutaneously across a loose pulmonary artery band

Transcatheter Pulmonary Flow Restrictors: Current Trends and Future Perspectives

BACKGROUND

Transcatheter Pulmonary Flow Restrictors (TPFRs) represent a significant advancement in managing pulmonary blood flow for congenital heart disease patients. However, there is a paucity of comprehensive studies addressing the diversity of these devices and identifying their critical features.

AIMS

This review aims to consolidate the existing knowledge on TPFRs, pinpoint crucial design and development aspects, identify gaps in current practices, and spotlight directions for future research and advancement.

METHODS

An exhaustive search was conducted across multiple databases, using specific search terms related to transcatheter and percutaneous pulmonary artery banding.

RESULTS

Between 2005 and 2024, 82 patients were reported to have received TPFR implants, including fenestrated atrial septal defect occluders, diabolo-shaped stents, and MVP™ Micro Vascular Plug with polytetrafluoroethylene (PTFE) membranes partially removed. Microvascular plugs were the most commonly used and the most successful devices. However, the primary complications and challenges associated with MVPs included pulmonary overflow, unprotected flow to the right upper lobe, difficulty in creating an appropriately sized fenestration, the need for device replacement due to incorrect sizing, distal migration into the right pulmonary artery, left pulmonary artery stenosis, partial device collapse, thrombosis, jailing of the right upper lobe, potential injury to the pulmonary arterial wall, as well as device fracture and infection. TPFRs can be categorized based on the duration they are designed to remain within the pulmonary artery. Strategies should be devised to enable the device's easy removal without harming the pulmonary arterial wall while also preventing embolization. The ideal device should minimize migration, embolization, thrombosis, inflammation, and endothelialization risks. It should also prevent peri-device flow and adapt to the growth of the pulmonary artery, ensuring long-term efficacy and safety.

CONCLUSION

The long-term outcomes and the potential for employing biodegradable and smart biomaterials remain areas for further investigation. Successful development of these devices requires a collaborative effort among biomaterial engineers, device developers, and interventional cardiologists.

Use of Flow Restrictors in Congenital Heart Disease

The surgical pulmonary artery band was first introduced in 1952 and, to this day, can produce challenges in regard to the ideal amount of restriction and the need for reoperations. A transcatheter option may be the ideal solution as it allows for a less-invasive approach for a better hemodynamic assessment and easier re-intervention. To date, multiple approaches have been developed with device modifications to create restrictions to flow, each with advantages and limitations. Continued experience is still necessary to determine the ideal device to use to create an adequate and modifiable level of restriction.

Outcomes of manually modified microvascular plugs to pulmonary flow restrictors in various congenital heart lesions

Background

The development of microvascular plugs (MVPs) has enabled novel transcatheter deliverable endoluminal pulmonary flow restrictors (PFRs) with the potential to treat newborns and infants with life-threatening congenital heart diseases (CHDs) in a minimally invasive manner. We present our experience to evaluate the efficacy of this concept in controlling pulmonary blood flow in various CHDs.

Methods

Retrospective clinical data review of patients with CHD and pulmonary over-circulation who received bilateral PFRs percutaneously.

Results

Twenty-eight PFRs (7 MVP-5Q, 12 MVP-7Q, and 9 MVP-9Q) were finally implanted in 14 patients with a median age of 1.6 months (IQR, 0.9-2.3) and a median weight of 3.1 Kg (IQR, 2.7-3.6). Nine patients had large intra-cardiac left-to-right shunts (including 3 with fatal trisomy and palliative programs), 2 had borderline left ventricles, 2 had Taussig-Bing anomaly, and one had a hypoplastic left heart. Four patients had concomitant ductal stenting. Two MVP-5Qs were snare-removed and upsized to MVP-7Q. Patients experienced a significant drop in oxygen saturation and Qp/Qs. All patients were discharged from the ICU after a median of 3.5 days (IQR, 2-5.8) postoperative. Five patients had routine inter-stage catheterization and no device embolization or pulmonary branch distortion was seen. Fourteen (50%) PFRs were surgically explanted uneventfully on a median of 4.3 months (IQR, 1.2-6) post-implantation during biventricular repair in 6 patients and stage-2 palliation in one patient. The latter died 1 month post-operative from severe sepsis. Four patients are scheduled for surgical PFR removal and biventricular repair. Two patients with trisomy 18 died at 1 and 6.8 months post-procedure from non-cardiac causes. One patient with trisomy 13 is alive at 2.7 months post-procedure.

Conclusion

It is feasible to bespoke MVPs and implant them as effective PFRs in various CHDs. This approach enables staged left ventricular recruitment, comprehensive stage-2 or biventricular repair with lower risk by postponing surgeries to later infancy. Device explantation is uneventful, and the outcomes afterward are promising.

Congenital heart disease: addressing the need for novel lower-risk percutaneous interventional strategies

INTRODUCTION

With the advent of improved neonatal care, increasingly vulnerable higher-risk patients with complex congenital heart anomalies are presenting for intervention. This group of patients will always have a higher risk of an adverse event during a procedure but by recognising this risk and with the introduction risk scoring systems and thus the development of novel lower risk procedures, the rate of adverse events can be reduced.

AREA COVERED

This article reviews risk scoring systems for congenital catheterization and demonstrates how they can be used to reduce the rate of adverse events. Then novel low risk strategies are discussed for low weight infants e.g. patent ductus arteriosus (PDA) stent insertion; premature infants e.g. PDA device closure; and transcatheter pulmonary valve replacement. Finally, how risk is assessed and managed within the inherent bias of an institution is discussed.

EXPERT OPINION

There has been a remarkable improvement in the rate of adverse events in congenital cardiac interventions but now, as the benchmark of mortality rate is switched to morbidity and quality of life, continued innovation into lower risk strategies and understanding inherent bias when assessing risk will be key to continuing this improvement.

Utility of the Medtronic microvascular plug™ as a transcatheter implantable and explantable pulmonary artery flow restrictor in a swine model

BACKGROUND

A surgical pulmonary artery band (PAB) is used to control excessive pulmonary blood flow for certain congenital heart diseases. Previous attempts have been made to develop a transcatheter, implantable pulmonary flow restrictor (PFR) without great success. We modified a microvascular plug (MVP) to be used as a PFR. The objectives of this study were to demonstrate feasibility of transcatheter implantation and retrieval of the modified MVP as a PFR, and compare PA growth while using the PFR versus PAB.

METHODS AND RESULTS

The PFR was implanted in eight newborn piglets in bilateral branch pulmonary arteries (PAs). Immediately post-PFR implantation, the right ventricular systolic pressure increased from a median of 20-51 mmHg. Transcatheter retrieval of PFR was 100% successful at 3, 6, and 9 weeks and 50% at 12-weeks post-implant. A left PAB was placed via thoracotomy in four other newborn piglets. Debanding was performed 6-weeks later via balloon angioplasty. On follow-up, the proximal left PA diameters in the PFR and the PAB groups were similar (median 8 vs. 7.1 mm; p = 0.11); albeit the surgical band sites required repeat balloon angioplasty secondary to recurrent stenosis. By histopathology, there was grade II vessel injury in two pigs immediately post-retrieval of PFR that healed by 12 weeks.

CONCLUSIONS

Transcatheter implantation and retrieval of the MVP as a PFR is feasible. PA growth is comparable to surgical PAB, which is likely to require reinterventions. The use of the MVP as a PFR in humans has to be trialed before recommending its routine use.