Modified Microvascular Plug as a Flow Restrictor in Hypoplastic Left Heart Syndrome with Dysplastic Tricuspid and Pulmonary Valves

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.

Percutaneous Pulmonary Flow Restriction in Infants With Congenital Heart Disease

Background

Restriction of PBF in infants born with CHD is often required to avoid pulmonary over-circulation prior to definitive intervention. The current standard is to surgically place pulmonary artery bands, but these have limitations and are associated with complications.

Objectives

The purpose of this study was to a single-center experience with a relatively novel technique to percutaneously restrict pulmonary blood flow (PBF) in select infants with congenital heart disease (CHD).

Methods

Patients were selected to undergo this procedure either due to low birth weight or prematurity. All of them had CHD that would result in over-circulation without control of PBF. By a percutaneous method, modified vascular plug devices were placed in the bilateral branch pulmonary arteries.

Results

Seven neonates with CHD resulting in left-sided obstruction underwent this procedure. All patients demonstrated evidence of restricted PBF with a decrease in mean oxygen saturation from 95% to 84%. One patient required pulmonary artery band placement due to over-circulation 5 days after the procedure. All patients proceeded to full surgical intervention without device embolization or need for pulmonary arterioplasty. Hemodynamics demonstrated adequate limitation of PBF in 5 patients who underwent presurgical cardiac catheterization with a mean pulmonary vascular resistance of 1.52 WU × m2 and a mean transpulmonary gradient of 5.9 mm Hg.

Conclusions

Percutaneous PBF restriction appears to be safe and a less invasive option to delay surgical intervention in a select population to allow for somatic growth and gestational maturation. It results in a decrease in the total number of sternotomies.

Use of a modified microvascular plug to modify fenestration flow in a rapidly failing Fontan

We report a case of an alternative transcatheter use of the modified Medtronic microvascular plug to modify fenestration stent flow in a patient with a rapidly deteriorating clinical condition. This four-year-old boy developed severe cyanosis following fenestration stent insertion, initially placed due to prolonged drainage post-Fontan with extra-cardiac conduit. In April 2023, he underwent urgent cardiac catheterisation and had partial occlusion of fenestration stent with a modified 9Q microvascular plug. His oxygen saturations improved from 50 to 89% in room air with no re-emergence of raised cavopulmonary pressures.

Transcatheter Palliation With Pulmonary Artery Flow Restrictors in Neonates With Congenital Heart Disease: Feasibility, Outcomes, and Comparison With a Historical Hybrid Stage 1 Cohort

BACKGROUND

Neonates with complex congenital heart disease and pulmonary overcirculation have been historically treated surgically. However, subcohorts may benefit from less invasive procedures. Data on transcatheter palliation are limited.

METHODS

We present our experience with pulmonary flow restrictors (PFRs) for palliation of neonates with congenital heart disease, including procedural feasibility, technical details, and outcomes. We then compared our subcohort of high-risk single ventricle neonates palliated with PFRs with a similar historical cohort who underwent a hybrid Stage 1. Cox regression was used to evaluate the association between palliation strategy and 6-month mortality.

RESULTS

From 2021 to 2023, 17 patients (median age, 4 days; interquartile range [IQR], 2-8; median weight, 2.5 kilograms [IQR, 2.1-3.3]) underwent a PFR procedure; 15 (88%) had single ventricle physiology; 15 (88%) were high-risk surgical candidates. All procedures were technically successful. At a median follow-up of 6.2 months (IQR, 4.0-10.8), 13 patients (76%) were successfully bridged to surgery (median time since PFR procedure, 2.6 months [IQR, 1.1-4.4]; median weight, 4.9 kilograms [IQR, 3.4-5.8]). Pulmonary arteries grew adequately for age, and devices were easily removed without complications. The all-cause mortality rate before target surgery was 24% (n=4). Compared with the historical hybrid stage 1 cohort (n=23), after adjustment for main confounding (age, weight, intact/severely restrictive atrial septum or left ventricle to coronary fistulae), the PFR procedure was associated with a significantly lower all-cause 6-month mortality risk (adjusted hazard ratio, 0.26 [95% CI, 0.08-0.82]).

CONCLUSIONS

Transcatheter palliation with PFR is feasible, safe, and represents an effective strategy for bridging high-risk neonates with congenital heart disease to surgical palliation, complete repair, or transplant while allowing for clinical stabilization and somatic growth.

Transcatheter Pulmonary Artery Banding in High-Risk Neonates: In-Vitro Study Provoked by Initial Clinical Experience

PURPOSE

Very high-risk, ductal-dependent or complex two-ventricle patients with associated comorbidities often require pulmonary blood flow restriction as bridge to a more definitive procedure, but current surgical options may not be well-tolerated. An evolving alternative utilizes a fenestrated Micro Vascular Plug (MVP) as a transcatheter, internal pulmonary artery band. In this study, we report a case series and an in-vitro evaluation of the MVP to elicit understanding of the challenges faced with device implantation.

METHODS

Following single-center, retrospective review of eight patients who underwent device placement, an in-vitro flow study was conducted on MVP devices to assess impact of device and fenestration sizing on pulmonary blood flow. A mathematical model was developed to relate migration risk to vessel size. Results of the engineering analysis were compared to the clinical series for validation.

RESULTS

At median follow-up of 8 months (range 1-15), survival was 63% (5/8), and 6 (75%) patients underwent subsequent target surgical intervention with relatively low mortality (1/6). Occluder-related challenges included migration (63%) and peri-device flow, which were evaluated in-vitro. The device demonstrated durability over normal and supraphysiologic conditions with minimal change in fenestration size. Smaller vessel size significantly increased pressure gradient due to reduced peri-device flow and smaller effective fenestration size.

CONCLUSION

Device oversizing, with appropriate adjustment to fenestration size, may reduce migration risk and provide a clinically appropriate balance between resulting pressure gradient and Qp:Qs. Our results can guide the interventionalist in appropriately selecting the device and fenestrations based on patient-specific anatomy and desired post-implantation flow characteristics.

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.