Bidirectional cavopulmonary anastomosis with additional pulmonary blood flow: good or bad pre-Fontan strategy

Utility of Balloon Occlusion Testing in Determining Fontan Suitability Among Patients with Elevated Pulmonary Artery Pressure and Additional Antegrade Pulmonary Blood Flow

In individuals with a single ventricle undergoing evaluation before Fontan surgery, the presence of excessive pulmonary blood flow can contribute to increased pulmonary artery pressure, notably in those who had a Glenn procedure with antegrade pulmonary flow. 28 patients who had previously undergone Glenn anastomosis with antegrade pulmonary blood flow (APBF) and with elevated mean pulmonary artery (mPAP) pressure > 15 mmHg in diagnostic catheter angiography were included in the study. After addressing other anatomical factors that could affect pulmonary artery pressure, APBF was occluded with semi-compliant, Wedge or sizing balloons to measure pulmonary artery pressure accurately. 23 patients (82% of the cohort) advanced to Fontan completion. In this group, median mPAP dropped from 20.5 (IQR 19-22) mmHg to 13 (IQR 12-14) mmHg post-test (p < 0.001). Median PVR post-test was 1.8 (IQR 1.5-2.1) WU m2. SpO2 levels decreased from a median of 88% (IQR 86%-93%) pre-test to 80% (IQR 75%-84%) post-test (p < 0.001). In five patients, elevated mPAP post-test occlusion on diagnostic catheter angiography led to non-completion of Fontan circulation. In this group, median pre- and post-test mPAP were 23 mmHg (IQR 21.5-23.5) and 19 mmHg (IQR 18.5-20), respectively (p = 0.038). Median post-test PVR was 3.8 (IQR 3.6-4.5) WU m2. SpO2 levels decreased from a median of 79% (IQR 76%-81%) pre-test to 77% (IQR 73.5%-80%) post-test (p = 0.039). Our study presents a specialized approach for patients initially deemed unsuitable for Fontan due to elevated pulmonary artery pressures. We were able to successfully complete the Fontan procedure in the majority of these high-risk cases after temporary balloon occlusion test.

Does leaving native antegrade pulmonary blood flow at the time of the superior cavopulmonary connection impact long-term outcomes after the Fontan?

Objectives

Antegrade pulmonary blood flow (APBF) may be left or eliminated at the time of the superior cavopulmonary connection (SCPC). Our aim was to assess the impact of leaving native APBF at the SCPC on long-term Fontan outcomes.

Methods

In the Australia and New Zealand Fontan Registry (1985-2021), 587 patients had pre-existing native APBF at the SCPC. At the SCPC, 302 patients had APBF eliminated (APBF-) and 285 patients had APBF maintained (APBF+). The incidence of Fontan failure (composite end point of Fontan takedown, transplant, plastic bronchitis, protein losing enteropathy and death) and atrioventricular (AV) valve repair/replacement post SCPC was compared between the 2 groups.

Results

Sex, predominant-ventricle morphology, isomerism, primary diagnosis, and age/type of Fontan were similar between groups. APBF- versus APBF+ had a higher incidence of arch obstruction/coarctation (17% vs 7%) and previous pulmonary artery band (54% vs 45%) and a lower rate of Fontan fenestration (27% vs 41%). The risk of Fontan failure was similar between the 2 groups (hazard ratio [HR], 1.01; 95% confidence interval [CI], 0.58-1.78; P = .96). The risk of AV-valve repair/replacement was greater in APBF+ versus APBF- (HR, 2.32; CI, 1.13-4.75; P = .022). The risk of AV-valve repair/replacement remained after adjustment for arch obstruction/coarctation, previous pulmonary artery band and Fontan fenestration (HR, 2.27; CI, 1.07-4.81; P = .033).

Conclusions

Maintaining APBF at the time of the SCPC does not impact the risk of Fontan failure but may increase the incidence of AV-valve repair and/or replacement post-SCPC.

Long-term results of additional pulmonary blood flow with bidirectional cavopulmonary shunt

Objective

We evaluated additional pulmonary blood flow at the time of bidirectional cavopulmonary shunt and its effects on the Fontan procedure and long-term outcome of Fontan circulation and liver function.

Methods

We included 22 patients (16 boys, 6 girls) having undergone bidirectional cavopulmonary shunt with additional pulmonary blood flow between April 2002 and January 2016. Mean age and body weight were 20 ± 13 months and 7.5 ± 6.5 kg, respectively. We retrospectively evaluated the patients’ clinical data, including cardiac catheterization data, liver function, and liver fibrosis markers.

Results

All patients were alive with a New York Heart Association status of I at the long-term follow-up. Changes between pre-bidirectional cavopulmonary shunt and 101 months after the Fontan procedure included the following: the cardiothoracic ratio of chest X-ray decreased from 52.2 ± 3.9% to 41.8 ± 5.9% (p < 0.001); systemic ventricle end-diastolic pressure decreased from 11.4 ± 3.2 mmHg to 6.9 ± 3.6 mmHg (p < 0.001); and the pulmonary artery index decreased from 485.1 ± 272.3 to 269.5 ± 100.5 (p = 0.02). Type IV collagen, hyaluronic acid, and procollagen levels increased over the normal range 116 months after the Fontan procedure.

Conclusions

The additional pulmonary blood flow at the time of bidirectional cavopulmonary shunt may contribute to pulmonary arterial growth at the Fontan procedure with low pulmonary arterial resistance and without ventricle volume overload. The Fontan circulation was well-maintained at the long-term follow-up, while liver fibrosis markers were above their normal values.

Hemodynamic Effects of Additional Pulmonary Blood Flow on Glenn and Fontan Circulation

PURPOSE

Additional pulmonary blood flow (APBF) can provide better pulsating blood flow and systemic arterial oxygen saturation, while low blood pulsation and low oxygen saturation are defects of the Fontan and Glenn procedure. Studying the hemodynamic effect of APBF is beneficial for clinical decisions. This study aimed to explore the effect on particle washout, as well as the differences among the sensitivities of both different hemodynamic parameters and different procedures to APBF.

METHODS

The patient-specific clinical datasets of a patient who underwent bilateral bidirectional Glenn (BBDG) with APBF were enrolled in this study, and using these datasets, Glenn- and Fontan-type artery models were reconstructed. A series of parameters, including the total caval flow pulsatility index (TCPI), indexed energy loss (iPL), wall shear stress (WSS), systemic arterial oxygen saturation (Sat_art), particle washout time (WOT), pressure in the right superior vena cava (P_RSVC), pulmonary flow distribution (PFD) and hepatic flow distribution (HFD), were computed from computational fluid dynamic (CFD) simulation to evaluate the hemodynamic effect of APBF.

RESULTS

The result showed that APBF led to better iPL and Sat_art but worse P_RSVC and heart load accompanied by a great impact on HFD, making hepatic flow easier to perfuse the side without MPA and APBF. The increase in the APBF rate also effectively results in larger flow pulsation, region velocity, and wall shear stress and lower WOT, and this effect may be more effective for patients with persistent left superior vena cava (PLSVC). However, APBF might have little effect on PFD. Furthermore, APBF might affect WOT, iPL and HFD more significantly than P_RSVC and has a greater improvement effect in patients with poorer iPL and WOT.

CONCLUSIONS

Moderate APBF is not only a measure to promote pulmonary artery growth and systemic arterial oxygen saturation but also an effective method against endothelial dysfunction and thrombosis. However, moderate APBF is patient-specific and should be determined based on hemodynamic preference that leads to desired patient outcomes, and care should be taken to prevent P_RSVC and heart load from being too high as well as an imbalance in HFD.

3D Simulation Analysis of Central Shunt in Patient-Specific Hemodynamics: Effects of Varying Degree of Pulmonary Artery Stenosis and Shunt Diameters

The objective of this study was to compare the effects of different shunt diameters and pulmonary artery (PA) stenosis grades on the hemodynamics of central shunts to determine an optimal surgical plan and improve the long-term outcomes of the operation. A 3D anatomical model was reconstructed based on the patient's clinical CT data. 3D computational fluid dynamics models were built with varying degrees of stenosis (the stenosis ratio α was represented by the ratio of blood flow through the main pulmonary artery to cardiac output, ranging from 0 to 30%; the smaller the value of α, the more severe the pulmonary artery stenosis) and varying shunt diameters (3, 3.5, 4, 4.5, and 5 mm). Our results show that the asymmetry of pulmonary artery flow increased with increasing shunt diameter and α, which will be more conducive to the development of the left pulmonary artery. Additionally, the pulmonary-to-systemic flow ratio (Q_P/Q_S) increases with the shunt diameter and α, and all the values exceed 1. When the shunt diameter is 3 mm and α = 0%, Q_P/Q_S reaches the minimum value of 1.01, and the oxygen delivery reaches the maximum value of 205.19 ml/min. However, increasing shunt diameter and α is beneficial to reduced power loss and smoother PA flow. In short, for patients with severe PA stenosis (α is small), a larger-diameter shunt may be preferred. Conversely, when the degree of PA stenosis is moderate, a smaller shunt diameter can be considered.