Outcomes of systemic to pulmonary artery shunts in patients weighing less than 3 kg: analysis of shunt type, size, and surgical approach

Surgical outcomes of the systemic-to-pulmonary artery shunt: risk factors of post-operative acute events and effectiveness of regulation of pulmonary blood flow with metal clips

OBJECTIVES

The aim of this study was to analyze the risk factors for acute events after systemic-to-pulmonary shunt (SPS) and to investigate the effectiveness of pulmonary blood flow regulation with a metal clip.

METHODS

The case histories of 116 patients (78 biventricular [BV] and 38 single ventricle [SV] physiology) who underwent SPS between 2010 and 2021 were retrospectively reviewed. Our strategy was to delay SPS until 1 month of age; pulmonary blood flow (PBF) regulation by partial clipping of the graft, if needed. Cases of aortic cross-clamping were excluded from this study.

RESULTS

CPB was used in 49 (42%) patients: the median age at SPS was 1 month (2 days to 16 years), and the sternotomy approach in 65. Discharge survival was 98.3% (114/116); hospital death occurred in 1.7% due to coronary ischemia. Inter-stage mortality occurred in 1.7% (shunt thrombosis, 1; pneumonia, 1). Pre-discharge acute events occurred in 7 patients (6.0%): thrombosis 3, pulmonary over-circulation 2, and coronary ischemia 2. Multiple logistic regression analysis revealed that pulmonary atresia with intact ventricular septum (PA/IVS) (p = 0.0253) was an independent risk factor for acute events. Partial clipping of the graft was performed in 24 patients (pulmonary atresia 15) and clip removal was performed by catheter intervention in 9 patients; no coronary ischemic events and graft injury occurred in these patients.

CONCLUSION

Surgical outcomes after SPS were acceptable and metal clip regulation of pulmonary blood flow appears to be safe and effective. PA/IVS was still a significant risk factor for acute events.

Congenital Non-Confluent Pulmonary Artery Sourced from Bilateral Arterial Ducts: A Rare Anomaly

This study aimed to identify the influence of the non-confluent pulmonary artery originating from the bilateral arterial ducts (AD) on the outcomes of the Fontan circulation. We retrospectively reviewed the records of nine patients with bilateral AD and a non-confluent pulmonary artery in a single ventricle at our institution between 1993 and 2023. Three patients showed maintained AD or underwent a systemic-pulmonary shunt for stenotic AD, followed by the Glenn procedure. Four patients underwent systemic-pulmonary shunt with angioplasty as the first palliation, followed by the Glenn procedure. Two patients underwent systemic-pulmonary shunt or AD stenting as the first palliation and systemic-pulmonary shunt with angioplasty as the second palliation. There were no cases of interstage mortality. Pulmonary arteries grew and achieved a good balance (pre-Fontan pulmonary artery index [PAI], 164 ± 27 mm2/m2; right/left PAI ratio, 1.06 ± 0.23). All patients underwent the Fontan procedure (median, 3.5 years; range, 2.3-6.4 years) and were followed up for 7.8 years (range, 0.1-16.4 years) after the procedure. One patient required hospitalization for heart failure at 1.8 years, and three patients required catheter intervention for pulmonary stenosis within 2 months after the Fontan procedure. Non-confluent pulmonary arteries originating from the bilateral AD do not preclude Fontan completion and good Fontan outcomes by restoring balance to pulmonary blood flow. Due to the limited sample size in this study, additional research is imperative to delve deeper into our findings and enhance understanding of the most effective surgical approach for this disease.

New approach in stage 1 surgery for hypoplastic left heart syndrome: preliminary outcomes

OBJECTIVES

We present the short-term results of an alternative method in stage 1 surgery for hypoplastic left heart syndrome.

METHODS

Data of 16 consecutive patients who were treated with the novel method in our clinic between February 2019 and March 2021 were analysed retrospectively. Preoperative data and postoperative follow-up were recorded.

RESULTS

Of the 16 operated patients, 12 were diagnosed with hypoplastic left heart syndrome, while four were diagnosed with hypoplastic left heart syndrome variants. Seven patients died during early postoperative period. One patient died at home waiting stage 2 surgery. Three patient underwent stage 2 surgery. Pulmonary artery reconstruction was performed in one patient due to left pulmonary artery distortion.

CONCLUSIONS

We believe that our method can be an effective alternative in the surgery of hypoplastic left heart syndrome and its variants. It is hoped that with increasing number of studies and more experience better outcome will be achieved.

Revisiting the central aortopulmonary shunt procedure

Background

In this study, we present our experience with the central aortopulmonary shunt technique with interposing a polytetrafluoroethylene graft between main pulmonary artery (end-to-end) and the ascending aorta (side-to-side) in a variety of cyanotic congenital heart defects.

Methods

Between January 2019 and June 2022, a total of 10 patients (6 males, 4 females; mean age: 4.3±2.8 months; range, 5 days to 10 months) with hypoplastic central pulmonary arteries who underwent central aortopulmonary shunt procedure were retrospectively analyzed. Demographic characteristics, preoperative, operative, and postoperative data of the patients were recorded. The Nakata indices of the patients were also noted before the procedure, as well as before the second stage of palliation or definitive repair.

Results

Four (40%) patients were operated as the first-step palliation for univentricular circulation. Six (60%) patients had well-developed ventricles and were palliated to be treated with total correction. The median follow-up after the procedure was 12 (range, 8 to 16) months. The mean systemic arterial saturation level at room air was 89.3±2.9% during follow-up. No mortality was observed in any patient.

Conclusion

A central aortopulmonary shunt procedure provides a reliable antegrade blood flow with a relatively non-challenging surgical technique that offers sufficient growth for the hypoplastic and confluent central pulmonary arteries with a very low risk of shunt thrombosis and overflow.

Stents as Bridge to Arterial Switch Operation for D-Transposition of Great Arteries Late Presenter

We report a 5-month-old infant with dextro-transposition of great arteries (D-TGA) with intact ventricular septum (IVS) who had low left ventricular mass index, small patent ductus arteriosus (PDA), and stretched patent foramen ovale. The patient had respiratory failure due to pneumonia. The surgical intervention was considered very high risk. Thus, the patient underwent PDA stenting with balloon predilation technique followed by atrial septal stenting with false impression of dislodgement-"pseudo-dislodgement" because of inadvertent retraction of patent foramen ovale that was confirmed by transthoracic echocardiography guidance. After the procedure, the left ventricular mass index improved and patient was planned for arterial switch operation. The combined approach of PDA and atrial septal stenting may provide potential nonsurgical method of ventricular preparation for D-TGA/IVS late presenter, acting as a bridge to arterial switch operation especially those living in remote areas.

Hemodynamic Response to Device Titration in the Shunted Single Ventricle Circulation: A Patient Cohort Modeling Study

Clinical outcomes of ventricular assist device (VAD) support for shunted single ventricle patients trail the larger population due in part to the challenges in optimizing VAD support and balancing systemic and pulmonary circulations. We sought to understand the response to VAD titration in the shunted circulation using a lumped-parameter network modeling six patient-specific clinical cases. Hemodynamic data from six patients (mean body surface area = 0.30 m2) with a systemic-to-pulmonary shunt was used to construct simulated cases of heart failure and hemodynamic response to increasing VAD flow from 5 to 10 L/min/m2. With increasing VAD flow, the pulmonary arterial pressure stayed relatively constant in five patient cases and increased in one patient case. The mean VAD flow needed to attain an arterial-venous O2 saturation difference of 30% was 6.5 ± 1.2 L/min/m2, which is higher than that in the equivalent nonshunted scenario due to the partial diversion of flow to the pulmonary circulation. The hemodynamic responses to VAD support can vary significantly between specific patient cases; therefore hemodynamic modeling may help guide an individualized approach to perioperative VAD management in the shunted single-ventricle circulation and to understand the patients who may benefit the most from VAD support.

Primary pulmonary artery reconstruction for functional single ventricle with absent central pulmonary artery and bilateral patent ductus arteriosus

OBJECTIVE

This study aimed to evaluate and discuss the outcomes of creating a single systemic-pulmonary shunt and reconstruction of the pulmonary artery continuity in patients with a single functional ventricle, absent central pulmonary artery, and bilateral patent ductus arteriosus.

METHODS

Six infants diagnosed with a functional single ventricle, absent central pulmonary artery, and bilateral patent ductus arteriosus were treated by creating a single systemic-pulmonary shunt and reconstructing the pulmonary artery continuity (primary operation) between January 2010 and September 2020. Pulmonary artery continuity was ensured using the remnant pulmonary artery and an autologous pericardial patch in five patients and a rolled autologous pericardium in one patient.

RESULTS

All patients eventually underwent total cavopulmonary connection. Two patients underwent intrapulmonary artery septation before Glenn or total cavopulmonary connection procedure. The median follow-up period was 9.02 years (interquartile range, 3.90-9.53). No late deaths were observed.

CONCLUSIONS

Our strategy of establishing a single systemic-pulmonary shunt with reconstruction of the pulmonary artery continuity was useful for treating patients with a functional single ventricle with absent central pulmonary artery and bilateral patent ductus arteriosus. This procedure helped accomplish pulmonary artery growth and ensured an appropriate volume load after total cavopulmonary connection.

Outcomes of duct stenting and modified Blalock-Taussig shunt in cyanotic congenital heart disease with duct-dependent pulmonary circulation

BACKGROUND

Transcatheter ductus arteriosus stenting (DS) is emerging as an alternative method to modified Blalock-Taussig shunt (MBTS) in providing pulmonary blood flow in cyanotic congenital heart disease (CCHD) with duct-dependent pulmonary circulation.

OBJECTIVE

To evaluate post-procedural outcomes and survival between patients undergoing DS and MBTS.

METHODS

All infants ≤ 60 days of age having CCHD with diminished pulmonary blood flow who underwent palliative procedure either with MBTS or DS at King Chulalongkorn Memorial Hospital during January 1st, 2013 and December 31th, 2017 were retrospectively reviewed.

RESULTS

98 patients were included; 34 patients underwent a transcatheter DS and 64 patients underwent MBTS. There was no significant difference in post-procedural outcomes and overall mortality rate between two groups (17.6% in MBTS group and 6.1% in DS group, p = 0.09). Single ventricle morphology was the major risk factor associated with increased mortality compared with biventricular morphology (aHR 3.9, 95% CI 1.49-10.2, p = 0.01). There was similar number of early and pre-repair additional interventions focusing on MBTS/DS patency between two groups. The MBTS group had a greater number of early interventions on PA branch stenosis related to baseline diagnosis. Risk factors associated with additional intervention were pre-existing pulmonary branch stenosis (aHR 2.54, 95% CI 1.3-4.97, p = 0.006) and body weight less than 2.5 kg (aHR 3.33, 95% CI 1.57-7.08, p = 0.003). Having pulmonic valve perforation or balloon pulmonary valvuloplasty to promote antegrade pulmonary blood flow could result in a lower number of additional interventions required before definitive repair.

CONCLUSION

Duct stenting is a feasible and safe alternative to MBTS in cyanotic infants with duct-dependent pulmonary circulation. However, mortality rate was significantly higher in patients with single ventricle that required careful follow-up after procedure.

Risk analysis for patients with a functionally univentricular heart after systemic-to-pulmonary shunt placement

OBJECTIVES

To investigate risk factors for mortality after systemic-to-pulmonary (SP) shunt procedures in patients with a functionally univentricular heart using the Japan Cardiovascular Surgery Database registry.

METHODS

Clinical data from 75 domestic institutions were collected. Overall, 812 patients with a functionally univentricular heart who underwent initial SP shunt palliation were eligible for analysis. Patients with pulmonary atresia with an intact ventricular septum and patients with a SP shunt as part of the Norwood procedure were excluded. Risk factors for 30- and 90-day mortalities were analysed using a logistic regression model.

RESULTS

Median age and body weight at SP shunt placement were 41 days and 3.6 kg, respectively. Modified Blalock-Taussig shunt, central shunt and other types of SP shunts were applied in 689 (84.9%), 94 (11.8%) and 30 (3.7%) patients, respectively. Cardiopulmonary bypass was utilized in 410 patients (51%) for 128 min (median, 19-561). There were 411 isolated SP shunt procedures. Median hospital stay was 27 days, and 742 (91.4%) patients were discharged. The 30- and 90-day mortality rates were 3.4% and 6.0%, respectively. Placement of a central shunt was identified as a risk factor for 30-day mortality, while lower body weight, preoperative ventilator support, right atrial isomerism and coexistence of major aortopulmonary collateral arteries and an unbalanced atrioventricular septal defect were identified as risk factors for 90-day mortality.

CONCLUSIONS

SP shunt carries a high mortality rate in patients with a functionally univentricular heart when it is performed in smaller patients with complex cardiac anomalies.

Transition to Ductal Stenting for Single Ventricle Patients Led to Improved Survival: An Institutional Case Series

BACKGROUND

The use of systemic-to-pulmonary shunts (SPS) in neonates with single ventricle heart defects and ductal-dependent pulmonary blood flow (ddPBF) was historically associated with high morbidity and mortality at our center. As a result, we transitioned to the preferential use of ductus arteriosus stents (DS) when feasible. This report describes our initial results with this strategy.

METHODS

A single-center study of single ventricle patients that received DS or SPS from 2015 to 2019 was performed to assess whether DS was associated with decreased in-hospital morbidity and increased survival to stage II palliation.

RESULTS

A total of 34 patients were included (DS = 11; SPS = 23). Underlying cardiac anomalies were similar between groups and included pulmonary atresia, unbalanced atrioventricular septal defect, and tricuspid atresia. Procedure success was similar between groups (82% vs 83%). Two DS patients were converted to SPS, due to ductal vasospasm or pulmonary artery obstruction, and four SPS patients required surgical shunt revision. In DS patients, postprocedure mechanical ventilation duration was shorter (one vs three days, P = .009) and fewer required postprocedure extracorporeal membrane oxygenation (9% vs 39%, P = .11). A higher proportion of DS patients survived to stage II palliation (100% vs 64%, P = .035), and the probability of one-year survival was higher in DS patients (100% vs 61%, P = .02).

CONCLUSIONS

At our center, patients with single ventricle heart defects and ddPBF that received DS experienced reduced in-hospital morbidity and increased survival to stage II palliation compared to SPS.

Growth of the Branch Pulmonary Arteries After Employing 'Shunt-Only' Strategy for Neonates With Pulmonary Atresia or Stenosis

We sought to determine the impact of juxtaductal stenosis (JDS) on branch pulmonary artery (PA) growth after systemic-to-pulmonary shunt (SPS) placement without pulmonary arterioplasty (ie the 'shunt-only' strategy). This was a retrospective review of 91 patients, 54 (59.3%) with pulmonary atresia and 27 (29.7%) with a functionally single ventricle, who underwent neonatal SPS placement without pulmonary arterioplasty between 2008 and 2017. The median age and body weight at SPS procedure were 16 day's (interquartile range [IQR], 11-22) and 3.10 kg (IQR: 2.85-3.40), respectively. All patients had pre-SPS computed tomography (CT) followed by post-SPS CT at a median interval of 5.8 months' (IQR: 4.5-7.2). The ratio of the diameters of the juxtaductal PA over the non-SPS-side hilar PA (JD and/or PA) on preoperative CT-a surrogate for JDS severity-was 0.93 (IQR: 0.67-1.09). The median diameter (Z) of the SPS-side and non-SPS-side PA on postoperative CT were 1.0 (IQR: -0.07-1.73) and 0.99 (IQR: -0.45-1.70), respectively. The pulmonary artery index (Nakata index) increased significantly from 124.0 ± 50.2 mm²/m² to 240.8 ± 88.7 mm²/m² (P < .001). Unplanned surgical interventions on the non-SPS-side PA were performed on 7 patients. Logistic regression identified lower preoperative JD and/or PA as a risk factor for unplanned intervention on the non-SPS-side PA (odds ratio, 1.27 per 0.1 decrease; 95% confidence interval, 1.10-2.16, P = 0.025). PA growth on the non-SPS side is generally adequate without pulmonary arterioplasty among patients with JDS. However, unplanned interventions for the non-SPS-side PA are caveats for 'shunt-only' strategy in neonates with significant JDS.

The Hemodynamics of Patent Ductus Arteriosus in Patients after Central Shunt Operation

A central shunt (CS) was an important surgery of systemic-to-pulmonary shunt (SPS) for the treatment of complex congenital heart diseases with decreased pulmonary blood flow (CCHDs-DPBF). There was no clear conclusion on how to deal with unclosed patent ductus arteriosus (PDA) during CS surgery. This study expanded the knowledge base on PDA by exploring the influence of the closing process of the PDA on the hemodynamic parameters for the CS model. The initial three-dimensional (3D) geometry was reconstructed based on the patient's computed tomography (CT) data. Then, a CS configuration with three typical pulmonary artery (PA) dysplasia structures and different sizes of PDA was established. The three-element windkessel (3WK) multiscale coupling model was used to define boundary conditions for transient simulation through computational fluid dynamics (CFD). The results showed that the larger size of PDA led to a greater systemic-to-pulmonary shunt ratio (Q _S/A), and the flow ratio of the left pulmonary artery (LPA) to right pulmonary artery (RPA) (Q _L/R) was more close to 1, while both the proportion of high wall shear stress (WSS) areas and power loss decreased. The case of PDA nonclosure demonstrates that the aortic oxygen saturation (Sao₂) increased, while the systemic oxygen delivery (Do₂) decreased. In general, for the CS model with three typical PA dysplasia, the changing trends of hemodynamic parameters during the spontaneous closing process of PDA were roughly identical, and nonclosure of PDA had a series of hemodynamic advantages, but a larger PDA may cause excessive PA perfusion and was not conducive to reducing cyanosis symptoms.

What are the non-cardiac prognostic factors affecting mortality in neonates with aortopulmonary shunt

Background/aim: Systemic to pulmonary shunts (SPS) have proven to be highly effective for the palliation of neonates with cyanotic congenital heart disease. Mortality after SPS surgery in neonates has multifactorial basis. We aimed to investigate the clinical results of the SPS in relation to the underlying cardiac disease and to identify the risk factors contributing to an adverse outcome.Material and method: All neonates who underwent first shunt insertion for cyanotic congenital heart disease during the study period from 1 January 2014 to 31 December 2017 were included. A retrospective review of patient records was done. Patients were grouped into two different categories: survived with or without any reintervention and death before or after any reintervention till discharge.Result: During the study period, 47 patients underwent SPS shunt placement. Patients who survived with or without any reintervention were in Group 1 and patients who died before or after any reintervention till discharge were in Group 2. Preoperative epinephrine requirement and mechanical ventilation and postoperative erythrocyte transfusion need were statistically significant.Conclusion: Although primary cardiac pathology is the most important prognostic factor, some other preoperative and postoperative factors like preoperative epinephrine requirement, and postoperative erythrocyte transfusion might also affect the prognosis. As there are very few centers in the region that specialize in pediatric cardiac surgery, a multicenter approach will be helpful in reaching reliable conclusions.

The efficiency of systemic-to-pulmonary shunts in older children with hypoplastic pulmonary arteries

BACKGROUND

To investigate the effects of systemic-to-pulmonary shunts (SPSs) in older children with hypoplastic pulmonary arteries and the factors affecting the development of the pulmonary arteries.

METHODS

Eighty-six children (older than 3 years) who received SPSs were retrospectively analyzed. The perioperative parameters, the postoperative diameter of the pulmonary artery were collected, and the factors influencing the growth of the pulmonary arteries after an initial palliative shunt operation were analyzed.

RESULTS

Two patients died postoperatively (2.33%), and the pulse oxygen saturation (SpO₂ ) increased from 71.70 ± 6.75% preoperatively to 85.20 ± 11.07% at discharge. During the follow-up period of 56 (10-99) months, 37 patients (43.02%) underwent subsequent procedures, and in the remaining patients, the McGoon ratio was increased from 0.96 ± 0.48 at the surgery to 1.30 ± 0.31 at the final assessment (P < 0.05). Univariate analysis indicated that age younger than 5 years old (P < 0.05), pulmonary artery forward flow (P < 0.05) and a diagnosis of tetralogy of Fallot (P < 0.05) played positive roles in the growth of the pulmonary artery after surgery, while children with a McGoon ratio less than 0.6 showed poor development of the pulmonary arteries (P < 0.05). Multivariate analysis showed that age younger than 5 years old (P < 0.05) and pulmonary artery forward flow (P < 0.05) were positive effectors on the growth of the pulmonary artery.

CONCLUSIONS

Older children with cyanotic congenital heart disease benefited from a systemic-pulmonary shunt and showed increased postoperative oxygen saturation and development of the pulmonary arteries. Age younger than 5 years and pulmonary artery antegrade flow were the positive factors influencing the growth of the pulmonary arteries postoperatively.

Blalock-Taussig Shunt Size: Should it be Based on Body Weight or Target Branch Pulmonary Artery Size?

The study aimed to revisit the in-hospital predictors of shunt thrombosis (ST) in the foreground of the pulmonary artery size in patients who received modified Blalock-Taussig shunt (mBTS) as the first-stage palliation. Data from 80 patients who received mBTS as their initial palliative procedure between February 2012 and January 2017 was retrospectively collected. The median age and weight of the patients at the time of their mBTS procedure was 4 days (IQR 2-22 days) and 3.2 kg (IQR 2.8-3.7 kg), respectively. Of the 80 patients in the study, 11 (13.8%) developed ST. The diameter and corresponding z scores of the pulmonary arteries were significantly lower in patients with ST. The median shunt size/shunted pulmonary artery size (S/PA) ratio was considerably higher in patients with ST. In logistic regression analysis, pulmonary artery hypoplasia (PAH) [odds ratio (OR) = 13.7 (0.06-0.21), p < 0.001], S/PA ratio ≥ 0.9 [OR = 8.1 (0.03-0.53), p = 0.03], prematurity [OR = 9.5 (0.05-0.33), p = 0.003], and shunt size/weight (S/W) ratio ≥ 1.3 [OR = 6.4 (0.04-0.67), p = 0.012] were found to have a significant impact on ST. The best combination of sensitivity and specificity of the S/W (0.73 and 0.75) and the S/PA ratio (0.73 and 0.80) were achieved at the cut-off value of 1.3 and 0.9, respectively. The Youden index of S/PA was 0.52. While the area under the curve (AUC) of the S/W ratio was 0.686 ± 0.12 (p = 0.049), the AUC of the S/PA ratio was 0.791 ± 0.08 (p = 0.002). In conclusion, instead of weight, considering the size of the target pulmonary artery and thereby, the S/PA ratio would be more instructive in determining shunt size. There were a high number of patients in our study who showed PAH having received a shunt size based on their body weight. By contrast, our results showed that the S/PA ratio of ≥ 0.9 would be a good predictor of in-hospital ST.

Major Adverse Events Following Over-Shunting Are Associated With Worse Outcomes Than Major Adverse Events After a Blocked Systemic-to-Pulmonary Artery Shunt Procedure

OBJECTIVES

Causes of major adverse event after systemic-to-pulmonary shunt procedure are usually shunt occlusion or over-shunting. Outcomes categorized on the basis of these causes will be helpful both for quality improvement and prognostication.

DESIGN

Retrospective cohort analysis of children who underwent a systemic-to-pulmonary shunt after excluding those who had it for Norwood or Damus-Kaye-Stansel procedure.

SETTING

The Royal Children's Hospital, Melbourne, VIC, Australia.

PATIENTS

From 2008 to 2015, 201 children who had a systemic-to-pulmonary shunt were included.

INTERVENTIONS

Major adverse event is defined as one or more of cardiac arrest, chest reopening, or requirement for extracorporeal membrane oxygenation. Study outcome is a "composite poor outcome," defined as one or more of acute kidney injury, necrotizing enterocolitis, brain injury, or in-hospital mortality.

MEASUREMENTS AND MAIN RESULTS

Median (interquartile range) age was 12 days (6-38 d) and median (interquartile range) time to major adverse event was 5.5 hours (2-17 hr) after admission. Overall, 36 (18%) experienced a major adverse event, and reasons were over-shunting (n = 17), blocked shunt (n = 13), or other (n = 6). Fifteen (88%) in over-shunting group suffered a cardiac arrest compared with two (15%) in the blocked shunt group (p < 0.001). The composite poor outcome was seen in 15 (88%) in over-shunting group, four (31%) in the blocked shunt group, and 56 (34%) in those who did not experience a major adverse event (p < 0.001). By multivariable analysis, predictors for composite poor outcome were major adverse event due to over-shunting (no major adverse event-reference; over-shunting odds ratio, 18.60; 95% CI, 3.87-89.4 and shunt-block odds ratio, 1.57; 95% CI, 0.46-5.35), single ventricle physiology (odds ratio, 4.70; 95% CI, 2.34-9.45), and gestation (odds ratio, 0.84/wk increase; 95% CI, 0.74-0.96).

CONCLUSIONS

Infants who suffer major adverse event due to over-shunting experience considerably poorer outcomes than those who experience events due to shunt block. A mainly hypoxic event with maintenance of systemic perfusion (as often seen in a blocked shunt) is less likely to result in poorer outcomes than those after a hypoxic-ischemic event (commonly seen in over-shunting).

Effect of modified Blalock-Taussig shunt anastomosis angle and pulmonary artery diameter on pulmonary flow

OBJECTIVE

This study aimed to identify the best graft-to-pulmonary artery (PA) anastomosis angle measuring pulmonary blood flow, wall shear stress (WSS), and shunt flow.

METHODS

A tetralogy of Fallot with pulmonary atresia computer model was used to study three different modified Blalock-Taussig shunt (mBTS) anastomosis angle configurations with three different PA diameter configurations. Velocity and WSS were analyzed, and the flow rates at the right PA (RPA) and left PA (LPA) were calculated.

RESULTS

A 4-mm and 8-mm diameter of RPA and LPA, respectively with vertical shunt angle produces the highest total flow. In the RPA larger diameter than the LPA configutations, the left-leaning shunt produces the lowest total PA flow whereas in the LPA larger diameter than the RPA configuratios, the right-leaning shunt produces the lowest total PA flow. Therefore, the shunt anastomosis should not be leaned through the narrow side of PA to reach best flow. As the flow inside the shunt increased, WSS also increased due to enhanced velocity gradients.

CONCLUSION

The anastomosis angle between the conduit and PA affects the flow to PA. Vertical anastomosis configurations increase the total PA flow; thus, these configurations are preferable than the leaned configurations.

Influence of weight at the time of first palliation on survival in patients with a single ventricle

BACKGROUND

Numerous advances in surgical techniques and understanding of single-ventricle physiology have resulted in improved survival. We sought to determine the influence of various demographic, perioperative, and patient-specific factors on the survival of single-ventricle patients following stage 1 palliation at our institution.

METHODS

We conducted a retrospective study of all single-ventricle patients who had undergone staged palliation at our institution over an 8-year period. Data were collected from the Society of Thoracic Surgeons Congenital Heart Surgery database and from patient charts. Information on age, weight at stage 1 palliation, prematurity, genetic abnormalities, non-cardiac anomalies, ventricular dominance, and type of palliation was collected. Information on mortality and unplanned reinterventions was also collected.

RESULTS

A total of 72 patients underwent stage 1 palliation over an 8-year period. There were 12 deaths before and one death after stage 2 palliation. There was no hospital mortality following Glenn or Fontan procedures. On univariate analysis, low weight at the time of stage 1 palliation and prematurity were found to be risk factors for mortality following stage 1 palliation. However, multivariable Cox regression analysis revealed weight at stage 1 palliation to be a strong predictor of mortality. The type of stage 1 palliation did not have any influence on the outcome. No difference in survival was noted following the Glenn procedure.

CONCLUSION

Low weight has a deleterious impact on survival following stage 1 palliation. This is mitigated by stage 2 palliation. The type of stage 1 palliation itself has no bearing on the outcome.

Experimental Study of Anisotropic Stress/Strain Relationships of Aortic and Pulmonary Artery Homografts and Synthetic Vascular Grafts

Homografts and synthetic grafts are used in surgery for congenital heart disease (CHD). Determining these materials' mechanical properties will aid in understanding tissue behavior when subjected to abnormal CHD hemodynamics. Homograft tissue samples from anterior/posterior aspects, of ascending/descending aorta (AA, DA), innominate artery (IA), left subclavian artery (LScA), left common carotid artery (LCCA), main/left/right pulmonary artery (MPA, LPA, RPA), and synthetic vascular grafts, were obtained in three orientations: circumferential, diagonal (45 deg relative to circumferential direction), and longitudinal. Samples were subjected to uniaxial tensile testing (UTT). True strain-Cauchy stress curves were individually fitted for each orientation to calibrate Fung model. Then, they were used to calibrate anisotropic Holzapfel–Gasser model (R2 > 0.95). Most samples demonstrated a nonlinear hyperelastic strain–stress response to UTT. Stiffness (measured by tangent modulus at different strains) in all orientations were compared and shown as contour plots. For each vessel segment at all strain levels, stiffness was not significantly different among aspects and orientations. For synthetic grafts, stiffness was significantly different among orientations (p < 0.042). Aorta is significantly stiffer than pulmonary artery at 10% strain, comparing all orientations, aspects, and regions (p = 0.0001). Synthetic grafts are significantly stiffer than aortic and pulmonary homografts at all strain levels (p < 0.046). Aortic, pulmonary artery, and synthetic grafts exhibit hyperelastic biomechanical behavior with anisotropic effect. Differences in mechanical properties among vascular grafts may affect native tissue behavior and ventricular/arterial mechanical coupling, and increase the risk of deformation due to abnormal CHD hemodynamics.

Outcomes of Blalock-Taussig shunts in current era: A single center experience

OBJECTIVES

Mortality associated with the modified Blalock-Taussig shunt (MBTS) remains high despite advanced perioperative management. This study was formulated to provide data on (1) current indications, (2) outcomes, and (3) factors affecting mortality and morbidity.

DESIGN

A retrospective single center chart review identified 95 children (excluding hypoplastic left heart lesions) requiring a MBTS. Mortality and major morbidity were analyzed using the Kaplan Meier method and risk factor analysis using Cox's proportional hazard regression.

RESULTS

Median age was 8 (0-126) days, weight 3.1(1.7-5.4) kg. Seventy-three percent were neonates, 58% duct dependent and 73% had single ventricle physiology. Ninety-seven percent had a sternotomy approach for shunt placement with 70% receiving a 3.5 mm graft. Mean graft index (shunt cross sectional area [mm² ]/BSA [m² ]) was 44.39 ± 8.04 and shunt size (mm) to body weight (kg) ratio 1.1 ± 0.2. Hospital mortality was 12%, with an interval mortality of 6%. Shunt thrombosis/stenosis occurred in 23% and pulmonary over circulation in 30%, while shunt reoperation was required in 12% and catheter intervention in 8% of the cohort. At 1-year, survival was 82.0% (95% CI [72.7%, 88.4%]), and survival free of major morbidity 61.4% (95% CI [50.7%, 70.5%]). Duct dependency predisposed to mortality (P = .01, HR 6.74 [1.54, 29.53]) and composite outcome (mortality and major morbidity) (P = .04, HR 2.15, CI [1.036, 4.466]) and higher graft index to mortality (P = .005, HR 1.07 [1.02, 1.12]).

CONCLUSIONS

The commonest indication for a MBTS in the current era was single ventricle palliation. Morbidity and mortality was considerable, partly explained by the higher at risk population. Alternative methods to maintain pulmonary blood flow in place of a MBTS requires further investigation.

Percutaneous intervention for central shunts: new routes, new strategies

Introduction In traditional locations, the standard Blalock-Taussig shunt presents numerous technical difficulties for percutaneous intervention. We changed our strategy to a central type shunt (Laks-type) with end-to-side pulmonary and side-to-side aortic anastomosis. The aim of this study was to determine whether this modified strategy would allow easier percutaneous manipulation in patients with small pulmonary arteries. Methods All children with a stretchable central vascular graft who required any form of percutaneous intervention were prospectively enrolled in the study. Results Eleven infants were evaluated a median time of 3 months (range 0.9-4.4) following initial shunt placement; the median weight at intervention was 5.7 kg (range: 4.0 - 10.0). All shunts (100%) were easily and swiftly entered without the need for special catheters or co-axial systems. In four patients other interventions in distal pulmonary arteries were first performed: cutting balloon treatment in three and balloon angioplasty of peripheral pulmonary artery stenosis in one. The shunts were then augmented with a stent with a diameter increasing from 3.5 ± 0.4 mm to 4.7 ± 0.8 mm and saturation increasing from 76% (range: 69-88) to 84% (range: 77-88) (P < 0.05). Several months later, two children required further interventions that could easily be performed via the stented shunts. No complications were observed. Conclusions The Laks-type shunt provides easy access for percutaneous procedures of the distal pulmonary arteries including cutting balloons; this shunt can predictably be expanded to augment pulmonary flow. This study highlights how co-operation between the interventionalist and the surgeon can improve strategies to manage these difficult patients.

Mathematical Analysis and Physical Profile of Blalock-Taussig Shunt and Sano Modification Procedure in Hypoplastic Left Heart Syndrome: Review of the Literature and Implications for the Anesthesiologist

The first stage of surgical treatment for hypoplastic left heart syndrome (HLHS) includes the creation of artificial systemic-to-pulmonary connections to provide pulmonary blood flow. The modified Blalock-Taussig (mBT) shunt has been the technique of choice for this procedure; however, a right ventricle-pulmonary artery (RV-PA) shunt has been introduced into clinical practice with encouraging but still conflicting outcomes when compared with the mBT shunt. The aim of this study is to explore mathematical modeling as a tool for describing physical profiles that could assist the surgical team in predicting complications related to stenosis and malfunction of grafts in an attempt to find correlations with clinical outcomes from clinical studies that compared both surgical techniques and to assist the anesthesiologist in making decisions to manage patients with this complex cardiac anatomy. Mathematical modeling to display the physical characteristics of the chosen surgical shunt is a valuable tool to predict flow patterns, shear stress, and rate distribution as well as energetic performance at the graft level and relative to ventricular efficiency. Such predictions will enable the surgical team to refine the technique so that hemodynamic complications be anticipated and prevented, and are also important for perioperative management by the anesthesia team.

Balancing pulmonary blood flow: Theory, in vitro measurements, and clinical correlation of systemic-to-pulmonary shunt banding

BACKGROUND

Size mismatch between body and a systemic-to-pulmonary shunt can result in excessive pulmonary blood flow, compromising systemic oxygen delivery. Previously reported techniques to mechanically restrict shunt flow lack precision and reproducibility. We developed a formula for shunt banding and assessed its efficacy and reproducibility by in vitro and clinical measurements.

METHODS

Formulas to determine diameter reduction, length of banding, and effect on the ratio of pulmonary blood flow (Q_p) to systemic blood flow (Q_s) were established. In vitro measurements of different shunt grafts were performed. Results were compared with calculations and clinical data. Clinical outcome was retrospectively assessed in all patients (n = 8) who underwent a shunt banding procedure at our institution between 2008 and 2012.

RESULTS

Our formulas can adequately predict the length of the band based on the desired diameter and shunt type or on the Q_p:Q_s mismatch. In vitro measurements correlated with the manufacturer's specifications in small shunts (≤5 mm diameter; 0.45 mm mean wall thickness). The calculated diameters of these shunts were closely correlated with in vitro measurements (r = 0.953; P = .001). Arterial saturation, pH, and calculated Q_p:Q_s decreased significantly with banding (P = .026, .002, and .004, respectively). Clinical effects varied among patients, with hemodynamically stable patients achieving the most benefit. Adjustment of the band was required in 1 patient. No shunt thrombosis or shunt banding-related complications were noted.

CONCLUSIONS

Our formulas and surgical strategy offer a new approach to controlling excessive pulmonary blood flow in shunt-dependent circulations in an effective and predictable way. The best reproducibility was achieved in small, thin-walled shunts. This strategy was most effective in patients with pulmonary overcirculation without hemodynamic decompensation.

Extracorporeal membrane oxygenator support in infants with systemic-pulmonary shunts

BACKGROUND

Management of a patent systemic-pulmonary (SP) shunt and the resulting runoff during extracorporeal membrane oxygenation (ECMO) varies among institutions. We have used a strategy of increased flow without surgical reduction of the shunt diameter, and here report our results with this strategy.

METHODS

In this database review of 169 successive veno-arterial ECMO runs performed between 2002 and 2013 in infants and neonates, ECMO flow, time to achieve lactate clearance, normal pH, and negative fluid balance were compared in patients with shunts and those without shunts.

RESULTS

Fifty-one of 169 infants (30.2%) had a shunt in situ when ECMO was initiated. Significantly higher ECMO flows were maintained in the shunt group compared with the nonshunt group (161 ± 43 mL/kg/minute vs 134 ± 41 mL/kg/minute; P < .001). Infants with shunts had significantly higher pre-ECMO and peak lactate levels (12.4 ± 5.6 mmol/L vs 10.0 ± 6.3 mmol/L; P < .05 and 13.7 ± 4.9 mmol/L vs 11.6 ± 5.5 mmol/L; P < .02, respectively) and required a longer period of support for clearance (median, 28.8 hours [16.1-63.3 hours] vs 17.5 hours [10.8-34.5 hours]; P < .001). Although the absolute rate of lactate clearance was not significantly different between the 2 groups (median, 0.46 mmol/L/hour [0.12-0.72 mmol/L/hour] vs 0.48 mmol/L/hour [0.22-0.86 mmol/L/hour]; P = .139) the presence of a shunt, neonatal age, peak lactate, extracorporeal cardiopulmonary resuscitation, and the use of hemofiltration on ECMO significantly predicted the rate of clearance. Survival to hospital discharge was similar in the shunt and nonshunt groups (49.0% vs 48.3%; P = .932).

CONCLUSIONS

A strategy of increased ECMO flow without surgically restricting shunt diameter appears to be successful in providing circulatory support in the majority of patients with an SP shunt. Equivalent survival suggests that routine surgical reduction of shunt diameter is not indicated.

Clinical assessment of diastolic retrograde flow in the descending aorta for high-flow systemic-to-pulmonary artery shunting

OBJECTIVE

To investigate whether echocardiographic characteristics in the descending aorta of patients with cyanotic congenital heart disease who have received a systemic-to-pulmonary artery (SP) shunt can indicate shunt flow volume and predict postoperative adverse events related to high-flow shunting.

METHODS

Among the 73 consecutive patients who received an SP shunt between 2010 and 2014, data for 53 patients who underwent postoperative Doppler echocardiographic assessment of diastolic retrograde flow in the descending aorta (dAo-RF) were reviewed retrospectively.

RESULTS

The mean dAo-RF ratio was 0.50 ± 0.15 at intensive care unit admission and reached its peak level (0.56 ± 0.12) at 24 hours after surgery. All of the patients with a maximal dAo-RF ratio of ≥0.80 had experienced acute heart failure or cardiogenic shock due to postoperative high-flow shunting and required emergent surgical interventions to reduce pulmonary blood flow. Pulse oximetry-measured oxygen saturation and serum lactate level were significantly correlated with dAo-RF ratio, but they had some clinical dispersion to match the postoperative adverse events.

CONCLUSIONS

The dAo-RF ratio is a simple, repeatable, and noninvasive index for postoperative assessment of SP shunt flow volume. A high dAo-RF ratio is a significant predictor of postoperative adverse events of high-flow shunting.

Management of the Preterm Infant with Congenital Heart Disease

The premature neonate with congenital heart disease (CHD) represents a challenging population for clinicians and researchers. The interaction between prematurity and CHD is poorly understood; epidemiologic study suggests that premature newborns are more likely to have CHD and that fetuses with CHD are more likely to be born premature. Understanding the key physiologic features of this special patient population is paramount. Clinicians have debated optimal timing for referral for cardiac surgery, and management in the postoperative period has rapidly advanced. This article summarizes the key concepts and literature in the care of the premature neonate with CHD.

Decision-Making for Surgery in the Management of Patients with Univentricular Heart

A series of technical refinements over the past 30 years, in combination with advances in perioperative management, have resulted in dramatic improvements in the survival of patients with univentricular heart. While the goal of single-ventricle palliation remains unchanged - normalization of the pressure and volume loads on the systemic ventricle, the strategies to achieve that goal have become more diverse. Optimal palliation relies on a thorough understanding of the changing physiology over the first years of life and the risks and consequences of each palliative strategy. This review describes how to optimize surgical decision-making in univentricular patients based on a current understanding of anatomy, physiology, and surgical palliation.

External counterpulsation of a systemic-to-pulmonary artery shunt increases coronary blood flow in neonatal piglets

BACKGROUND

Systemic-to-pulmonary artery shunt (SPS) palliation reduces coronary blood flow (CBF), which may precipitate myocardial ischemia postoperatively.

HYPOTHESIS

Counterpulsation (CP) of SPS augments CBF.

METHODS

Seven neonatal piglets (4.3 ± 0.23 kg) underwent sternotomy and ductus ligation. With a 5-mm polytetrafluoroethylene graft, SPS was created from innominate to pulmonary artery. A rigid shell holding a 9.5-mm diameter balloon was placed around the graft for CP. Using electrocardiographic signal, CP was initiated to trigger balloon inflation/deflation during the diastolic/systolic intervals, respectively. Instantaneous proximal and distal pulmonary artery and mid-anterior descending coronary artery flow rates were measured using transit time flow probes. Blood pressure and flow rates were recorded during three states: shunt closed, shunt open, and shunt open with CP.

STATISTICAL COMPARISON

Friedman's test and repeated measures analysis of variance.

RESULTS

Diastolic pressure decreased significantly with the shunt open (39 ± 8.4 to 28 ± 4.5 mm Hg, P = .05), then increased with CP (33 ± 2.3 mm Hg, P = .03). Median ratio of pulmonary to systemic flow (Qp/Qs) was 1.19, 1.9, and 1.53 with shunt closed, open, and open with CP, respectively. With CP, both diastolic coronary flow per minute (P = .018) and average diastolic flow rate per diastolic interval (P = .03) increased as well as total coronary flow per minute (P = .066; 19.6% ± 11.7%, 25.2% ± 17.0%, and 15.4% ± 13.9% change from shunt open, respectively). The percentage increase in average diastolic flow rate per diastolic interval correlated strongly with Qp/Qs (R (2) = .838).

CONCLUSIONS

In this model of SPS, CP increased diastolic blood pressure and CBF while maintaining significant augmentation of pulmonary blood flow (Qp/Qs). Shunt CP may aid in early postoperative management of palliative congenital heart disease.