2.1 hPAB Procedural Technique

The bilateral PAB technique has been previously described, with an excellent technical description by Zampi et al. [10-12]. All but one case (40% O₂) was performed in room air. To summarize, GoreTex bands were placed around each branch PA off CPB at a starting circumference of 7 mm regardless of size. After initial application of the bilateral PAB, a sheath was placed directly into the main PA, secured via a purse string suture and snared to allow fixation of the sheath. The interventional team then proceeded with branch PAB assessment, first with a main PA angiogram. A PAB was adjusted if clinical parameters (e.g., systemic saturation/BP and/or angiography) were out-of-range; repeat clinical and angiographic assessment was performed in those cases. Once angiography and clinical parameters were in-range, pressure-wire assessment of each branch PA was then performed in all patients. Given the narrow diameter of the branch PAB, we favor pressure-wire assessment over the use of larger microcatheters, which may obstruct flow and affect pressure readings. Specifically, a Glidecath catheter with Bentson-Hanafee-Wilson 1 distal curvature (Terumo Corp, Tokyo, Japan) was advanced to the main PA and utilized to direct a Pressure Wire X (Abbott, Lake County, IL USA) wire into each branch PA, with the sensor approximately 1−2 cm distal to the band and in the main branch PA lumen (Figure 1). The pressure wire was calibrated per manufacturer instructions. Goal branch PA mean pressures were < 20 mmHg with PA pulse pressure of 4−6 mmHg [12]. The PABs were secured to the PA adventitia in two locations, using 7−0 Prolene, to prevent distal migration.

Indications to adjust a branch PAB were based on a non-algorithmic assessment of absolute and change from baseline in systemic arterial saturations and PO₂, qualitative angiographic appearance of the banded branch PAs, and absolute and relative bilateral PA mean and pulse pressure. Regarding angiography, bands were considered appropriately restrictive if there was a visible and narrow (~2−3 mm diameter) waist at the site of application with relatively equal distribution of contrast and subsequent clearance through both PAs. An aforementioned vascular clip was removed for an overly restrictive band or an additional clip was applied if inadequate flow restriction. If adjustment of one or both bands was performed, both branch PAs were reassessed with angiography and pressure-wire measurement (Figure 2).

2.2 Concomitant and Subsequent Operative Procedures

Additional procedures performed at the time of hPAB were abstracted. These procedures included balloon atrial septostomy (BAS) and patent ductus arteriosus (PDA) stenting. Pulmonary arterioplasty was typically performed as part of the hPAB debanding procedure. For patients following a single ventricle pathway, a modified Stage 1 Norwood procedure was subsequently performed, which included PA debanding and augmentation with placement of either an RV-PA conduit (aka “Sano”) or Blalock-Taussig-Thomas (BTT) shunt. These patients typically underwent bidirectional Glenn (BDG) procedure at the traditional age following the modified Stage 1 Norwood operation. For patients with biventricular circulation, PA debanding and augmentation was performed contemporaneously with definitive biventricular repair.

2.3 Hemodynamics and Measurement of Pulmonary Arterial Growth

All catheterizations after the hPAB procedure were reviewed for all patients and hemodynamic data were recorded. With bilateral PAB in place, branch PA size was measured by angiography immediately distal to the band. As the PA band was typically immediately adjacent to a lobar branching point (e.g., right upper and intermediate PA), each segmental RPA diameter was measured, and values summated to calculate a composite branch PA measure. After branch PA debanding, branch PA diameter was measured immediately proximal to hilar branching by angiography, when obtained, and echocardiography. Branch PA measures are reported as both raw data and indexed to body surface area (BSA). In addition, post-hPAB procedure echocardiographic data were obtained, including spectral Doppler gradients and branch PA measures after debanding.

The Nakata index was calculated at hPAB procedure, after debanding, and most recent follow-up using the previously described formula [1, 2]. We measured branch PA Z-score and PA symmetry, defined as the ratio of the smaller to larger branch PA areas, expressed as a percentage.

2.4 Subsequent PA Interventions

All transcatheter and operative PA interventions performed on all hPAB patients were abstracted. Operative PA intervention was defined as any surgical procedure that involved pulmonary arterioplasty. As above, pulmonary arterioplasty is typically performed at the time of debanding and was not counted as a reintervention. Catheter-based interventions included PA balloon angioplasty with or without stent implantation.

2.5 Statistical Analysis

Statistical analysis was conducted using JMP (JMP Statistical Discovery LLC, Cary, NC). Standard descriptive statistics were performed. The paired t test was used to compare continuous variables. A two-sample proportion test was used to compare proportional variables. Time-to-event outcomes (freedom from PA intervention) were assessed with Kaplan−Meier survival estimates (log-rank test for difference between strata, p < 0.05).

3.1 Hemodynamics

Table 2 includes procedural hemodynamics at the hPAB procedure. Median final PA pressures in all patients were 18 mmHg [range 14−21] in the RPA and 17 mmHg [range 14−19] in the LPA with similar median RPA and LPA pulse pressures of 4 mmHg (range 4−6 mmHg). Among the adjustments for an overly restrictive band, median pre-revision RPA pressure was 12 mmHg [range 12−13] with pulse pressure of 2 mmHg [range 1−2] and median LPA pressure was 11.5 mmHg [range 6−14] with pulse pressure of 1 mmHg [range 0−2]. Among the nine patients who underwent PAB revision for hypoxemia or angiographic appearance, arterial oxygen saturation increased from a nadir of 66% ± 9% after initial application of the bilateral PAB to 86% ± 8% (p < 0.004) after adjustment. Regarding the six who underwent revision based on out-of-range pressures, saturations did not significantly change (pre-revision 82% ± 3% and vs. post-revision 81% ± 2%).

3.2 Pulmonary Arterial Reinterventions

Five patients—1 single-ventricle and 4 two-ventricle—underwent a total of 13 procedures to intervene on the branch PAs after hPAB (Table 3). One underwent reintervention only in the interstage, three underwent reintervention only after the subsequent operation, and one underwent reinterventions both during the interstage and after repair. The five patients had a median of two reinterventions [range 1−4] each, at a median interval of 111 days [IQR 82−242] after hPAB procedure. Four patients had only transcatheter reinterventions while one had both transcatheter and surgical revisions.

Of the 13 procedures, 12 were transcatheter and 1 was surgical. As above, 2 of the 12 transcatheter reinterventions were performed during the interstage, both involving angioplasty of a bPA band in the setting of hypoxemia related to somatic growth; neither had undergone PAB revision at the time of the hybrid procedure. One of those was in a single-ventricle patient, at 47 days post-hPAB, with RPA band angioplasty alone. The other was a biventricular patient, 142 days after hPAB, involving bilateral PAB angioplasty. The remaining 10 catheterizations were performed after debanding, all on patients with two-ventricle circulation. The single operative PA revision was performed on a patient with Taussig-Bing type DORV who had undergone DORV repair involving a LeCompte maneuver. He underwent repeat operation for LPA arterioplasty and transannular patch related to combined RV outflow and LPA obstructions; this patient went on to have 3 transcatheter bPA angioplasties of the LPA.

Of the total 46 bPAs banded in the cohort, 2 RPAs underwent reintervention after debanding, comprising 17% of the 12 survivors' RPAs. One intervention involved RPA angioplasty alone and the other an RPA stent implant. As for the LPA, 10 underwent reintervention, 90% of survivors' LPAs, with eight angioplasty-only and two LPA stent implants.

Freedom from PA reintervention is shown in Figure 4. Though sample sizes are limited, freedom from reintervention was similar among patients who underwent intraoperative revision and those who did not.

3.3 Pulmonary Arterial Size, Growth, and Symmetry

Table 4 outlines longitudinal PA measures for the cohort. Branch PA sizes were in the normal range at the time of the hPAB procedure with no significant difference between patients who underwent branch PAB revision and those who did not (Nakata 245 ± 65 vs. 237 ± 59 respectively, p = 0.02). PA parameters remained in the low-normal range at most recent follow-up, again with no significant differences between the revision and no revision patients (239 ± 26 vs. 259 ± 42 respectively, p = 0.03). Patients with single ventricle physiology had final PA measures that were slightly smaller than the biventricular patients, consistent with other published findings in single ventricle patients (225 ± 14 in single ventricle vs. 286 ± 26 in biventricular patients, p = 0.01) [13].

From a PA symmetry standpoint, symmetry was 91% ± 5% at completion of the hPAB procedure. Symmetry for the entire cohort was 91% ± 7% at most recent follow-up, with no significant differences based on circulation type (92% ± 5% single ventricle vs. 90% ± 11% two ventricles, p = 0.2) or performance of intra-operative band revision (91% ± 6% revised vs. 91% ± 9% no revised, p = 0.4). Central illustration 1

3.4 Final Status of Hpab Patients

Fifteen patients (65%) survived to repair/Stage 2, which was performed at a median age 127 days [range 31−242]. Eight proceeded to a univentricular palliation and underwent BDG, six underwent biventricular repair, and one received an OHT shortly after hPAB. All patients with univentricular circulation remained hospitalized after the hPAB procedure until the Stage 1 Norwood. Conversely, 2 of the patients with biventricular circulation were discharged after the hPAB while four remained hospitalized until repair. After the index operation, 14 patients were ultimately discharged (8 uni- and 6 biventricular), at a median age of 45 days [range 24–89].

Overall mortality was 48% (N = 11). Of the eight who died before the next planned operation, seven had univentricular circulation. The median age of interstage death was 11 days [range 4−60] in those with univentricular lesions (Table 5). Of the three who died after debanding, one had undergone biventricular repair, was discharged at 79 DOL, subsequently hospitalized on at 9 months of age for respiratory decompensation, and ultimately died at 11 months of age (352 days after the hPAB procedure) with in-home hospice. The second patient underwent BDG and was discharged at 49 days of age, developed significant ventricular dysfunction, and received an OHT (727 days after hPAB) after prolonged hospitalization; this patient died 161 days post-transplant. The final patient underwent BDG and was discharged on DOL 106; the patient later died at 3 years of age (3.9 years after hPAB procedure) after in-hospital cardiac arrest during an admission for pneumonia.

4.1 Limitations

Ours is a retrospective review of one a single cohort, without a direct comparison, at a single center. Duration of follow-up (mean 25 months) is relatively short. Further, the heterogeneity of the cohort may independently influence short- and long-term outcomes independent of the effects of hPAB. And since hPAB is not widely performed, threshold pressures were developed a priori, and further study may suggest finer calibration of goal pressures. And though we evaluated PA reinterventions and growth, long-term quantitative branch PA flow data were limited in our cohort. Future studies comparing this technique with traditional branch PA band placement can help better understand the effect on subsequent pulmonary arterial interventions, measured branch PA flow symmetry, Fontan candidacy, and other clinical outcomes.

4.2 Conclusions

The pressure-wire assisted hPAB procedure is a useful technique that helps identify patients with overly restrictive bands that may not be identified by traditional clinical markers—BP and saturations—or angiography. These real-time data provide an opportunity for intraoperative adjustment with the goal of achieving symmetric PA flow.