Univentricular Anatomy Research Articles

Sutureless Repair of Extracardiac Univentricular Total Anomalous Pulmonary Venous Connection

BackgroundThis study aimed to evaluate the results of sutureless repair of extracardiac total anomalous pulmonary venous connection (TAPVC) with a functional single ventricle at a single institution, including changes in the anastomotic site over time. MethodsThe database contained 98 patients with single-ventricle anatomy who underwent extracardiac TAPVC repair from 1996 to 2022. The median age and body weight at surgery were 59 days and 3.8 kg, respectively. Eighty-seven patients had heterotaxy syndrome, and 42 had preoperatively obstructed TAPVC. Primary sutureless repair was performed in 18 patients, 13 of whom were neonates. The cross-sectional area of the anastomotic site of the atrium and pericardium was divided by the body surface area, and the changes in this value over time were assessed. The median follow-up was 5.2 years (range, 0-19.4 years). ResultsOperative mortality and late mortality occurred in 2 (2.0%) and 38 (38.8%) patients, respectively. The actuarial survival rate at 5 years postoperatively was 56.2%. Multivariate analysis identified preoperatively obstructed TAPVC as a risk factor for mortality. Recurrent pulmonary venous stenosis (PVS) developed in 25 patients, thus giving a 5-year rate of freedom from PVS of 64.9%. Multivariate analysis revealed that sutureless repair significantly decreased the incidence of recurrent PVS. The cross-sectional anastomotic area tended to grow in accordance with the patients’ growth. ConclusionsSutureless repair of extracardiac TAPVC with univentricular anatomy achieved acceptable results. The anastomotic site tended to grow over time and contributed to a decline in the rate of recurrent PVS.

Outcomes in very low birthweight infants with severe congenital heart defect following cardiac surgery within the first year of life.

Very low birthweight (<1500 g, VLBW) infants with severe congenital heart defect (CHD) are at increased risk for perinatal and operative mortality. This study aims to describe morbidity, long-term mortality and neuro-developmental outcome in early childhood in VLBW infants who received cardiac surgery for severe CHD within 1 year after birth. Monocentric observational study on VLBW infants with severe CHD born between 2008 and 2017. Neurodevelopmental impairment at 2 years corrected age was defined as cognitive deficit, cerebral palsy or major neurosensory deficit. A total of 24 patients were included. Twenty-one (87.5%) infants underwent cardiac surgery with hypothermia during cardiopulmonary bypass (median temperature 30.3°C, interquartile range 27.0-32.0°C) at a median age of 96 (40-188) days. Seven (29.2%, 95% confidence interval 14.9-49.2%) patients died within the first year after cardiac surgery. Survival rates decreased with increasing STAT mortality category of the surgical procedure. Neurodevelopmental impairment at 2 years of corrected age was found in 9 out of 17 (52.9%) surviving infants, with 8 infants (47.1%) presenting with a cognitive deficit or delay and 4 infants (23.5%) being diagnosed with cerebral palsy. Survival without neuro-developmental impairment was 29.2% (n = 7, 95% confidence interval 14.9-49.2%) in the entire study cohort. Eighty percent of the newborns with dextro-transposition of the great arteries, but no patient with univentricular anatomy, survived without neuro-developmental impairment. Individual VLBW infants with severe CHD may develop well despite the high combined risk for adverse outcomes. The type of cardiac malformation may affect early- and long-term outcomes.

Effects of levosimendan on ventriculo-arterial coupling and cardiac efficiency in paediatric patients with single-ventricle physiology after surgical palliation: retrospective study.

The use of levosimendan for paediatric patients with low cardiac output after congenital heart surgery has been recently described. We sought to evaluate ventriculo-arterial coupling (VAC) and other ventricular energetic parameters before and after 72 h from levosimendan start in infants with single-ventricle physiology and cardiac failure after palliation with Norwood or hybrid procedures. In this single-centre retrospective study, 9 consecutive patients affected by hypoplastic left heart syndrome-like anatomy were retrospectively analysed. Systolic elastance, diastolic elastance, arterial elastance, VAC and cardiac mechanical efficiency were calculated by measuring, through 2-dimensional echocardiography, end-systolic volume and end-diastolic volume and by recording mean arterial pressure and central venous pressure. The median (range) weight and age were 2.8 (2.3-6) kg and 16.5 (6-116) days, respectively. After 72 h from levosimendan start, end-systolic volume significantly decreased (-1 ml, -3.2 to -0.1, P = 0.007), whereas mean arterial pressure and end-diastolic volume remained stable. Heart rate showed a significant decrease (-28 beats/min, -41 to 22, P = 0.008). Systolic elastance (2.9 mmHg/ml, 0.4-5.4, P = 0.008), arterial elastance (-5.9, -24 to -0.5, P = 0.038), VAC (-0.86, -1.5 to -0.16, P = 0.009) and cardiac mechanical efficiency (0.18, 0.03-0.22, P = 0.008) differences also showed significant modifications. In a small case series of patients with single-ventricle physiology, levosimendan showed to improve contractility and optimize VAC, with a reduction of heart rate. Monitoring of VAC and ventricular energetics can be an interesting aspect to improve the management of heart failure in infants with univentricular anatomy.

219-01: The subcutaneous ICD in congenital heart disease – challenges and chances

Purpose of the study: Transvenous ICD therapy faces relevant limitations and contraindications in patients with congenital heart disease (CHD). The recently introduced entirely subcutaneous implantable cardioverter-defibrillator (S-ICD) offers a relevant alternative, as it does not need vascular access or thoracotomy. Methods used: S-ICD system was implanted in a heterogeneous group of 10 patients with structural CHD (age 8.9–62.0 y, height 73.0–208.0 cm, weight 34.0–130.0 kg). The majority presented with challenging hemodynamic and anatomical features such as univentricular anatomy, cavo-pulmonary anastomosis, dextrocardia, severe scoliosis, mechanical circulatory support (VAD due to failing systemic right ventricle in cc-TGA) and tricuspid valve dysplasia (Ebstein's anomaly); one patient suffered from Tetralogy of Fallot (TOF) with multiple previous surgery and another from juvenile HOCM. In 9 of 10 patients ICD was implanted due to secondary prophylaxis. Primary indication to opt for S-ICD as the first choice were: missing transvenous access (2), right-to-left shunt as contraindication for transvenous leads (4), avoidance of tricuspid valve passage (2) and young age without pacing indication (1). In one patient (with VAD) a pre-existing transvenous ICD had been removed due to chronic lead-associated infection and replaced by a right-sided S-ICD, combined with epicardial pacing. All patients were eligible by surface ECG template screening. Lead and device positioning was anatomically adapted and modified by pre-implant fluoroscopy to achieve an optimized intrathoracic electric field. Two systems were implanted in mirrored position in patients with dextrocardia, one lead was placed right parasternal and 9 of 10 devices implanted submuscular. Summary of results: After uneventful implantation successful DFT testing applying a 15 J safety margin confirmed correct function in all. Follow-up was performed up to 5 years. Cosmetic results were good with no pocket-related issues even in the smallest subjects. 3 patients – all with RBBB - suffered from inappropriate shocks due to altered T wave morphology under higher heart rate resulting in t-wave-oversensing (TWOS). This could be overcome by acquiring a new template under maximum exercise. The patient with TOF had multiple appropriate shocks from monomorphic VTs but also developed slow VTs below the shock zone (<170/min) and severe chronotropic incompetence. Therefore he was switched to a transvenous system with improved clinics due to the availability of pain free overdrive stimulation (ATP) and antibradycardiac pacing. The VAD patient died during follow-up of unknown reason. Conclusion: S-ICD therapy is feasible even in complex CHD patients, for whom conventional transvenous ICD concepts are not applicable. As this may avoid risks and burden associated with surgical lead placement, it represents an attractive new therapeutic modality. Due to the vast heterogeneity in size and anatomy, together with frequent alterations in excitation propagation and repolarization in this group, an advanced and thorough pre-implantation screening is mandatory. Modifications in lead and device arrangement supported by preoperative fluoroscopy are necessary, to ensure correct arrhythmia detection and therapy delivery even in distorted anatomy. The presumably higher incidence of TWOS has to be considered, although modified programming may resolve the issue. With submuscular placement, cosmetic and functional results are excellent; nevertheless the bulky size of the device currently precludes its use below a weight of approx. 30 kg. Despite successful application with combined (epicardial) pacing, the lack of antibrady- and -tachycardiac pacing currently represents the major limitation towards widespread use in the field of CHD.

Neurodevelopmental Outcomes After Open Heart Operations Before 3 Months of Age

The purpose of this study was to monitor developmental progress and identify predictors of developmental outcomes at 2 years after operation in infants who underwent a surgical procedure with cardiopulmonary bypass (CPB) at less than 3 months of age. Patients (N=131 enrolled; N=106 assessed) less than 3 months of age at the time of cardiac operation were prospectively enrolled (years 1999-2003) and assessed at 8, 12, and 24 months after operation. Patients with preexisting conditions independently associated with poor neurodevelopmental outcomes were excluded. Fine and gross motor development was formally assessed at all 3 visits, and parent ratings of development across several domains were obtained. Neurodevelopment was formally assessed at 24 months of age using the Bayley Scales of Infant Development, 2nd edition (BSID-II) Mental Development Index score (MDI). Significant gross motor difficulties were identified at 8 months of age (p<0.001) and, although improved by the 24-month assessment, remained lower than average. Fine motor skills showed a significant decrease from 8 to 24 months of age (p=0.001). Factors associated with poorer neurodevelopmental outcome (BSID-II MDI) at 24 months after operation included a diagnosis of univentricular anatomy or complex coarctation of the aorta, higher complexity of the surgical procedure, longer duration of hospital stay, and presence of complications in the postoperative period. Children undergoing repair of congenital heart disease (CHD) still have impaired development 2 years after the operation. Observed patterns of development were specific to the skill being assessed and related to both anatomic complexity and increased complexity of care received.

Upper cavo‐pulmonary anastomosis by transcatheter technique

The aim of this animal study was to establish a shunt connection between superior vena cava (SVC) and right pulmonary artery (RPA) by transvascular intervention solely. After initial shunt creation, the establishment of the upper cavo-pulmonary anastomosis (UCPA) is the second out of three open chest operations young infants with univentricular anatomy are subjected to. To avoid the risks of reoperation with cardiovascular bypass, we sought to replace this surgical step by an interventional technique. After cannulation of jugular and femoral veins in four piglets (mean body weight of 12.5 kg) an UCPA was created by radiofrequency perforation from the SVC across the right atrium into the RPA and subsequent implantation of covered stents. The perforation was guided by biplane fluoroscopy and the perforation wire premounted with a coaxial catheter was advanced into the distal pulmonary artery and exchanged for a stiffer wire. A long sheath was brought into the RPA and an 80 mm long expanded poly-tetra-fluoro-ethylene (ePTFE)-covered Cheatham Platinum stent was then implanted connecting the SVC with the RPA. Immediate angiography showed antegrade flow from SVC to RPA. Angiographic re-evaluation after a median period of 4 weeks showed partial in-stent stenosis but patent lumina. Additionally, veno-venous collaterals from the SVC to the right atrium had developed. Histology of the explanted stents revealed parietal thrombi and mild to moderate pseudo intima proliferation inside the lumina. The transvascular creation of an upper unidirectional cavo-pulmonary anastomosis in piglets is technically feasible using standard catheterization equipment.

Early Outcomes of Primary Sutureless Repair of the Pulmonary Veins

The "sutureless" repair technique has improved outcomes for post-repair pulmonary vein (PV) stenosis. The purpose of this study is to determine the early outcomes of primary sutureless repair of pulmonary venoocclusive disease in infants with congenital PV stenosis-hypoplasia or PVs at high risk for progressive stenosis. This is a retrospective review of infants who had primary sutureless repair of the PVs from October 2002 to April 2010. Twenty-five infants had primary sutureless repair of the PVs. Eighteen infants had total anomalous pulmonary venous return; 14 with obstruction, 10 with heterotaxy syndrome, and 9 with univentricular anatomy. Seven infants had congenital PV stenosis. There were 24 perioperative survivors (96%; 95% confidence interval [CI], 75% to 99%) and 2 late deaths from extracardiac causes. Follow-up was available on 21 out of 22 survivors at a median duration of 34 months (range, 9 to 100 months). Persistence-recurrence of PV stenosis occurred in 3 veins (3%) of 2 infants (8%). On follow-up echocardiography, right ventricular systolic pressure was normal in 13 out of 14 infants with a biventricular heart and 60% of systemic blood pressure in 1 infant. Kaplan-Meier 1-year cumulative survival was 88% (95% CI, 66% to 96%). Kaplan-Meier cumulative disease-free survival was 96% (95% CI, 75% to 99%) at 30 days and 84% (95% CI, 58% to 95%) at 1 year. By Cox proportional hazards, age, univentricular anatomy, and atrial isomerism-heterotaxy syndrome were not associated with an increased risk of death or persistence-recurrence. One-year disease-free survival was lower in infants with prematurity (p=0.0055) and low birth weight (p=0.0011). Primary sutureless repair is a feasible, safe, and relatively effective method of addressing congenital PV stenosis and (or) high-risk PVs, particularly in infants with single ventricle anatomy and (or) heterotaxy syndrome.

Generalised muscle weakness in young adults with congenital heart disease

BackgroundIn patients with heart failure from acquired cardiomyopathy, respiratory and skeletal muscle weakness is common and is an independent predictor for adverse events. Despite a different underlying pathology, many young...

Initial Single-Center Experience With Levosimendan Infusion for Perioperative Management of Univentricular Heart With Ductal-Dependent Systemic Circulation

The aim of this study was to evaluate the safety and the efficacy of levosimendan, a novel calcium sensitizer agent, on postoperative hemodynamic and metabolic parameters of neonates affected by single ventricle anatomy. Twenty consecutive neonates scheduled for the Norwood procedure with Blalock Taussig shunt were prospectively enrolled. All patients received an infusion of levosimendan at 0.1 μg/kg/min commencing 24 hours before surgery, and the infusion was continued for 48 hours after surgery. No side effects (intolerance to the drug, hypotension, arrhythmias) were shown. A median inotropic score (IS) of 37 was necessary to maintain a mean arterial pressure between 45 and 50 mm Hg at intensive care unit (ICU) admission: IS was significantly reduced after 72 hours (P < .05). Brain natriuretic peptide values decreased significantly from 1210 to 459 pg/mL in 72 hours (P < .05). Median SvO2 increased significantly from 38% to 59% during the evaluated period (P < .05). Cerebral near-infrared spectroscopy values were close to 40% at ICU admission with a significant stable increase to 50% after 12 hours (P < .05). Median lactate level was 13 mmol/L at ICU admission but showed a trend to a rapid and significant decrease after 12 hours (P < .05). Median urine output was surprisingly elevated, always remaining between 5.2 and 6.2 mL/kg/h throughout the postoperative period. Survival rate was 85% at 30 days (17/20 patients) and 75% (15/20) at hospital discharge. Levosimendan infusion in a cohort of neonates with univentricular anatomy was safe and potentially beneficial on postoperative hemodynamic and metabolic parameters.

Safety of intravenous use of ketorolac in infants following cardiothoracic surgery

To evaluate the impact of intravenous ketorolac on renal function and haematologic values in patients less than six months old following cardiothoracic surgery. Ketorolac is a potent nonsteroidal anti-inflammatory drug indicated for short term management of moderate to severe post-operative pain. Little data is available related to its safety in infants less than six months of age. This was a retrospective, case-control chart review of 19 patients aged less than six months of age with biventricular circulations who received intravenous ketorolac following cardiothoracic surgery. They were compared with 19 age-matched control patients. Those with functionally univentricular anatomy were excluded due to their higher risk for renal impairment following surgery. Student's t-test was used to compare the incidence of renal impairment and haematologic complications between the groups, as well as the number of analgesic doses administered. Charts were reviewed for number of blood transfusions. Patients receiving intravenous ketorolac had no statistically significant changes in pre-operative versus post-treatment renal function or haematologic effects compared to the control group. No statistically significant differences were detected for number of post-operative blood transfusions or additional analgesic administration between groups. Intravenous ketorolac appears to be safe when used in infants less than six months of age with biventricular circulations following cardiothoracic surgery. Ketorolac as used in these patients does not decrease the use of standard analgesic therapy.

Clinical outcome of patients 20 years after Fontan operation — effect of fenestration on late morbidity

The Fontan operation has been proposed as definitive palliation for an increasing variety of hearts with complex univentricular anatomy, but late morbidity after Fontan operation is still a matter of concern. This retrospective study evaluates the late outcome in patients with Fontan circulation. We included 121 consecutive patients that underwent Fontan operation between 1984 and 2004. Modifications of the Fontan operation included atriopulmonary anastomosis (APA; n = 28), total cavopulmonary connection (TCPC; n = 63), and fenestrated TCPC (f-TCPC; n = 30). Mean age was 5.8+/-5.5 years. Post operative mortality, morbidity, hemodynamics, and somatic development were analyzed. Actuarial survival was 87% at 20 years after Fontan operation. There were 10 early deaths, 5 late deaths, and 2 takedowns followed by successful conversion and heart transplantation. Among 108 early-survivors with Fontan circulation, 19 underwent reoperation, including 3 conversions of APA to TCPC. Freedom from reoperation was 76% at 20 years. Freedom from intervention was 34% at 20 years. Freedom from tachyarrhythmia or pacemaker implantation was 23% and 77%, respectively at 20 years. Heterotaxy and atrioventricular valve anomaly were risk factors for late failure and tachyarrhythmias. Patients with fenestrated TCPC had reduced incidence of late tachyarrhythmias, and patients with APA who developed collaterals showed low incidence of late tachyarrythmia. Postoperative sinus node dysfunction or tachyarrhythmias was associated with significantly lower cardiac index. Somatic development was gradually compensated after Fontan operation. Weight normalized completely 15 years postoperatively. Long-term survival after Fontan procedure is encouraging, but late morbidity remains suboptimal. During follow-up, emerging complications should be managed by surgical and interventional procedures. Fenestration in Fontan circulation provided better cardiac output and lower incidence of late tachyarrhythmias, suggesting a benefit of fenestration for late outcome.

Cardiac anomalies in patients with congenital diaphragmatic hernia and their prognosis: a report from the Congenital Diaphragmatic Hernia Study Group

Background/Purpose Patients with congenital diaphragmatic hernia (CDH) are known to have associated cardiac anomalies. Data from the Congenital Diaphragmatic Hernia Study Group has allowed better definition of the types of heart defects (HDs) and survival for these patients. Methods Since 1995, 2636 patients were enrolled in the Congenital Diaphragmatic Hernia Study Group from 82 centers. Patients with hemodynamically significant HD, excluding patent ductus arteriosus (PDA); patent foramen ovale (PFO); and atrial septal defect (ASD), were selected. Cardiac anatomy and survival data for all patients were reviewed. Results Two hundred eighty (10.6%) patients had significant HDs: ventricular septal defect (VSD); (42.2%), aortic arch obstruction (15%), univentricular anatomy (13.9%), tetralogy of Fallot variants (11.1%), total anomalous pulmonary venous return (3.9%), double outlet right ventricle (RV) (3.2%), pulmonary stenosis (2.5%), transposition of the great arteries (2.5%), and various other defects in 5.7%. Survival for the entire group was 67.1%; survival for patients without HD was 70.2% and for patients with HD was 41.1% ( P < .001). Patients with biventricular cardiac anatomy had a 47% survival, whereas those with univentricular anatomy had a 5% survival ( P < .001). Conclusion Significant HD is associated with 10.6% of CDH. Survival for patients with HD is significantly lower than for patients with normal cardiac anatomy. Patients with CDH and univentricular cardiac anatomy have a poor prognosis.

Optimal surgical approach for repair of aortopulmonary window

This is a review of the experience over 26 year in a single institution with surgical repair of aortopulmonary window. Between July 1973 and March 1999, 38 patients underwent surgery for aortopulmonary window at a median age of 5 weeks, and with a median weight of 3.9 kg. Median follow-up was 6.6 years, with a range from 0.8 to 26 years. Additional defects were present in 25 (65%) patients, including interruption of the aortic arch in 7, tetralogy of Fallot in 7, ventricular septal defect in 5, functionally univentricular anatomy in 3, aortic coarctation in 2, and anomalous origin of a coronary artery in 1. We approached via an aortotomy in 45%, an incision through the defect in 31%, and using a pulmonary arteriotomy in 24% of patients. Closure was achieved using a single patch in 30 patients (79%). There were 3 (7.9%) in-hospital deaths. Actuarial patient survival was 88% at 10 years. Three patients required reinterventions for stenoses of the great arteries. Freedom from any reintervention was 70% at 10 years. By multivariate analysis, the approach through a pulmonary arteriotomy was shown to result in a higher need for reintervention (p = 0.01). Repair of aortopulmonary window can be done with excellent results. A pulmonary arteriotomy should be avoided.

Commentary

Commentary

Centrifugal ventricular assist in children under 6 kg.

The clinical application of centrifugal ventricular assist devices (VAD) has generally been limited to adults and large paediatric patients. In our experience neonates and small paediatric patients requiring ventricular support post-cardiopulmonary bypass are well supported by VAD. In this study we analyse our experience. We have examined the records of our VAD patients who weighed less than 6 kg. Thirty-four patients, ranging in age from 2 to 258 days (median 60 days) and weight from 1.9 to 5.98 kg (median 3.7 kg), underwent 35 VAD procedures. One patient was supported on VAD twice. All patients had congenital heart lesions and were placed on VAD either because they could not be weaned from cardiopulmonary bypass after repair or palliation of the lesion (71.5%), or for support in the post-operative period due to refractory low cardiac output (28.5%). Twenty-two of the 35 VAD procedures (0.63, 95% CI: 0.45-0.78) resulted in successful weaning and decannulation, this was similar to the weaning probability for patients greater than 6 kg (P = 0.07). There were 10 late deaths in this group, with a 1-year KM survival of 0.31 (95% CI: 0.17-0.47). Most late deaths were related to irreversible cardiac disease processes as were the elective discontinuance of VAD outcomes. Neither weight, age, VAD duration, CPB duration, X clamp duration, univentricular anatomy or TGA anatomy predicted successful discharge from hospital (P > 0.05)--Weight P = 0.576; Age P = 0.532; VAD duration P = 0.181; CBP duration P = 0.549; X clamp duration P = 0.984; Univentricular anatomy P = 0.481; TGA anatomy P = 0.099. We believe centrifugal ventricular assist is a realistic option in very small patients who require post-cardiopulmonary bypass support. It is relatively easy to establish and manage, the results, although showing no factors predictive of successful discharge, are encouraging.

Modified fontan operation in functionally univentricular hearts: Preoperative risk factors and intermediate results

Background: The modified Fontan operation has been proposed as definitive palliation for an increasing variety of hearts with complex univentricular anatomy. To eliminate the influence of different surgical strategies, only patients undergoing total cavopulmonary anastomosis were included in this retrospective study. Methods: Seventy-two patients had been operated on at ages ranging from 7 to 219 months, with 29 patients younger than 4 years. Twenty-three patients had mean pulmonary artery pressures higher than 15 mm Hg, elevated pulmonary arteriolar resistances (>3 U · m 2), or elevated end-diastolic ventricular pressure (>12 mm Hg). Associated systemic or pulmonary venous anomalies were present in 22 patients (30%), and atrioventricular valve incompetence was present in 21 patients (29%). Results: The overall mortality rate was 9.7% (7/72). Variables with significant effects on postoperative mortality were associated systemic or pulmonary venous anomalies, atrioventricular valve incompetence, mean pulmonary artery pressure greater than 15 mm Hg, and prolonged cardiopulmonary bypass time. Postoperative morbidity resulted mainly from atrial arrhythmia (20%). Clinical signs of protein-losing enteropathy or atrial thrombi were rare (3% and 6%, respectively). Postoperative hemodynamic data from 48 surviving patients (74%) revealed a mean transpulmonary gradient of 6.3 mm Hg, systemic venous pressure greater than 12 mm Hg in only 10 patients, and cardiac index less than 3 L · min -1 · m -2 in 18 patients. Conclusion: In a high proportion of hearts with complex univentricular anatomy, associated anomalies, and borderline hemodynamics, the Fontan operation can be performed as a total cavopulmonary anastomosis with acceptable intermediate postoperative morbidity and hemodynamic results. (J T HORAC C ARDIOVASC S URG 1996;112:658-64)

Central pulmonary artery growth patterns after the bidirectional Glenn procedure

The changes in pulmonary artery size and hemodynamics in 30 patients with univentricular cardiac anatomy were examined before and after bidirectional Glenn procedures done between October 1989 and February 1992. Serial angiographic and hemodynamic examinations before and 17.6 +/- 1.6 months after bidirectional Glenn procedures were compared. At the follow-up study there was no significant change in diameter of the pulmonary artery ipsilateral to the bidirectional Glenn shunt, however, a significant decrease was noted in the diameter of the pulmonary artery contralateral to the bidirectional Glenn shunt (p = 0.04). There was also a 32% decrease in the Nakata index of total cross-sectional pulmonary artery area after the bidirectional Glenn procedure (p = 0.004). Total pulmonary blood flow and mean pulmonary artery pressure had decreased, and arterial oxygen saturation had increased at follow-up. These changes, however, did not correlate with the observed changes in pulmonary artery size. By linear regression analysis, a significant relationship was identified between the Nakata index before the bidirectional Glenn procedure and the absolute change in Nakata index (r = 0.83). A significant decrease in Nakata index occurred only in patients with a bidirectional Glenn shunt in place more than 15 months. Sixteen of the 30 patients subsequently underwent total cavo-pulmonary anastomosis with 7 requiring concurrent surgical pulmonary artery reconstruction. Changes in pulmonary artery size observed more than 15 months after the bidirectional Glenn procedure may have implications for subsequent Fontan repair in children with univentricular anatomy.