Risk factors for development of endocarditis and reintervention in patients undergoing right ventricle to pulmonary artery valved conduit placement

Diepoxy- Versus Glutaraldehyde-Treated Xenografts: Outcomes of Right Ventricular Outflow Tract Reconstruction in Children

BACKGROUND

Xenografts used for right ventricular outflow tract (RVOT) reconstruction are typically treated with glutaraldehyde. However, potential benefit of epoxy treatment was demonstrated in experimental studies. We aimed to compare diepoxy-treated bovine pericardial valved conduits (DE-PVCs) and glutaraldehyde-treated bovine pericardial valved conduits (GA-PVCs) for RVOT reconstruction in pediatric patients.

METHODS

Between 2002 and 2017, 117 patients underwent RVOT reconstruction with PVC in single center: DE-PVC group, n = 39; and GA-PVC group, n = 78. After performing propensity score analysis (1:1) for the entire sample, 29 patients from the DE-PVC group were matched with 29 patients from the GA-PVC group.

RESULTS

There were no conduit-related deaths. In the DE-PVC group, the freedom from conduit failure was 90.9% at four years and 54.3% at eight years postoperatively. In the GA-PVC group, it was 46.3% and 33.1%, respectively. The difference was significant (P = .037). Conduit failure was typically caused by stenosis in both groups. In the DE-PVC group, the main cause of stenosis was xenograft calcification (27.6%); while in the GA-PVC group, it was mostly due to neointimal proliferation (25.0%) and, less often, calcification (14.3%). Conduit thrombosis was the cause of replacement in 6.9% of patients from the GA-PVC group.

CONCLUSIONS

Diepoxy-treated bovine pericardial valved conduit is a suitable alternative to GA-PVC for RVOT reconstruction in pediatric patients. Diepoxy-treated bovine pericardial valved conduits may be less prone to conduit failure and more resistant to neointimal proliferation and conduit thrombosis than GA-PVCs.

Endocarditis After Transcatheter Pulmonary Valve Replacement

BACKGROUND

Endocarditis has emerged as one of the most concerning adverse outcomes in patients with congenital anomalies involving the right ventricular outflow tract (RVOT) and prosthetic valves.

OBJECTIVES

The aim of this study was to evaluate rates and potential risk factors for endocarditis after transcatheter pulmonary valve replacement in the prospective Melody valve trials.

METHODS

All patients in whom a transcatheter pulmonary valve (TPV) was implanted in the RVOT as part of 3 prospective multicenter studies comprised the analytic cohort. The diagnosis of endocarditis and involvement of the TPV were determined by the implanting investigator.

RESULTS

A total of 309 patients underwent transcatheter pulmonary valve replacement (TPVR) and were discharged with a valve in place. The median follow-up duration was 5.1 years, and total observation until study exit was 1,660.3 patient-years. Endocarditis was diagnosed in 46 patients (median 3.1 years after TPVR), and a total of 35 patients were reported to have TPV-related endocarditis (34 at the initial diagnosis, 1 with a second episode). The annualized incidence rate of endocarditis was 3.1% per patient-year and of TPV-related endocarditis was 2.4% per patient-year. At 5 years post-TPVR, freedom from a diagnosis of endocarditis was 89% and freedom from TPV-related endocarditis was 92%. By multivariable analysis, age ≤12 years at implant (hazard ratio: 2.3; 95% confidence interval: 1.2 to 4.4; p = 0.011) and immediate post-implant peak gradient ≥15 mm Hg (2.7; 95% confidence interval: 1.4 to 4.9; p = 0.002) were associated with development of endocarditis and with development of TPV-related endocarditis (age ≤12 years: 2.8; 95% confidence interval: 1.3 to 5.7; p = 0.006; gradient ≥15 mm Hg: 2.6; 95% confidence interval: 1.3 to 5.2; p = 0.008).

CONCLUSIONS

Endocarditis is an important adverse outcome following TVPR in children and adults with post-operative congenital heart disease involving the RVOT. Ongoing efforts to understand, prevent, and optimize management of this complication are paramount in making the best use of TPV therapy. (Melody Transcatheter Pulmonary Valve [TPV] Study: Post Approval Study of the Original Investigational Device Exemption [IDE] Cohort; NCT00740870; Melody Transcatheter Pulmonary Valve Post-Approval Study; NCT01186692; and Melody Transcatheter Pulmonary Valve [TPV] Post-Market Surveillance Study; NCT00688571).

0.1 mm ePTFE versus autologous pericardium for hand-sewn trileaflet valved conduit: a comparative study

A hand-sewn trileaflet valved conduit is reportedly better than a bovine jugular graft. However, the comparative efficacy and safety between 0.1 mm ePTFE and autologous pericardium in this surgical procedure remained undetermined. This single-center cohort study included 46 patients aged 3–146 months who received implanted simplified hand-sewn trileaflet valved conduits: 31 patients (Group A) received 0.1 mm ePTFE valved conduits and 15 patients (Group B) received autologous pericardium valved conduits. Perioperative and follow-up outcomes up to 3 years after the surgeries were evaluated. No perioperative complications or early mortality were observed in either group, while one Group A patient aged 46 months died 6 months after surgery due to residual ventricular septal defect. No patients in Group A developed severe regurgitation or stenosis in valves of the conduits, but two moderate stenosis by echocardiography, and seven patients in group B were deemed to be conduit dysfunction (two stenosis, three stenosis plus regurgitation, and the remaining two regurgitation). No conduits failure was detected in group A, while two patients in group B (one for severe stenosis and the other one for severe regurgitation). After 6, 12, and 36 months, 95.2%, 88.9%, and 88.9% of Group A patients and 92.3%, 68.4%, and 42.7% of Group B patients were free from valved conduit dysfunction. After the same follow-up periods, all Group A patients had no conduit failure and 92.3%, 80.8%, and 80.8% of Group B patients were free from valved conduit failure. Within the 3-year follow-up period, 0.1 mm ePTFE novel simplified hand-sewn trileaflet valved conduits appear to be associated with a lower incidence of graft failure than autologous pericardium valved conduits.

Clinical Characteristics of Infective Endocarditis in Children

BACKGROUND

Infective endocarditis (IE) remains a diagnostic and therapeutic challenge associated with high morbidity and mortality. We evaluated the microbial profile and clinical manifestation of IE in children.

METHODS

A retrospective study examining pediatric IE cases treated between 2000 and 2017 at the Department of Pediatric Cardiology, KU Leuven, was conducted. Clinical presentation, treatment, complications, outcome of IE, underlying microorganisms and congenital heart defects were reviewed.

RESULTS

Fifty-three patients were diagnosed with IE. Overall, 19 patients (36%) required cardiac surgery. Seven patients (13%) died. Eighty-seven percent of patients had an underlying congenital cardiac defect. Eighteen (34%) children presented with prosthetic graft IE. A causative organism was found in 49 (92%) cases: viridans group streptococci were identified in 17 (32%), Staphylococcus aureus in 13 (25%) and coagulase-negative staphylococci in 11 (20%) children. Community-acquired (CA) IE increased significantly from 8 (33%) cases in 2000-2007 to 20 (74%) cases in 2008-2017 (P < 0.01). Even with viridans streptococci being significantly more prevalent in the CA group (P < 0.01), we did not observe an increase of streptococcal IE from 2008 to 2017. Seventeen (32%) patients presented with hospital-acquired IE during the first year of life with 14 (82%) children after surgery and a prevalence of coagulase-negative staphylococci (53%).

CONCLUSIONS

The incidence of pediatric IE was similar over the investigated time period with a shift toward CA IE. Streptococci and staphylococci accounted for the majority of cases in both periods. Awareness of IE and its prevention is crucial in patients after implantation of prosthetic grafts.

Outcomes of Prosthetic Valved Conduits for Right Ventricular Outflow Tract Reconstruction

There are limited data regarding the implantation of prosthetic valved conduits for right outflow tract reconstruction in pediatric patients in China. A retrospective review of 128 patients undergoing conduits implantation with a median follow-up of 33.3 months (range, 3.3 months to 10.1 years) was performed between 2009 and 2018. Multivariate Cox regression model was used to analyze the risk factors for mortality, reintervention and endocarditis. Freedom from reintervention and endocarditis were plotted using the Kaplan-Meier curve. Hospital mortality was 7.8%, and the late mortality was 3.1%. Patient survival at 1, 5 and 10 years was 92.2%, 87.1% and 84.3%, respectively. Freedom from reintervention at 1 and 5 years was 94.1% and 60.9%. Small size conduit (p = 0.019) and previous palliation (p < 0.001) were predictive of reintervention. Ten conduits developed endocarditis at a median of 4.8 years after implantation. Freedom from endocarditis at 1, 5 and 10 years was 99.1%, 93.0% and 58.0%, respectively. Diffuse stenosis of the conduit (p = 0.003) was an independent risk factor for late endocarditis. Both bovine jugular venous conduits and bovine pericardial prosthetic conduits are associated with acceptable outcomes. Reintervention remains high in patients who have smaller size conduit and undergo previous palliation. It is plausible that the suboptimal flow may be one of major mechanisms involved in the development of late endocarditis.

Contegra versus pulmonary homograft for right ventricular outflow tract reconstruction in newborns

OBJECTIVES

Pulmonary homografts are standard alternatives to right ventricular outflow tract reconstruction in congenital heart surgery. Unfortunately, shortage and conduit failure by early calcifications and shrinking are observed for small-sized homografts in younger patients. In neonates, Contegra® 12 mm (Medtronic Inc., Minneapolis, Minnesota, United States of America) could be a valuable alternative, but conflicting evidence exists. There is no published study considering only newborns with heterogeneous pathologies. We retrospectively compared the outcomes of these two conduits in this challenging population.

METHODS

Patients who underwent a right ventricular outflow tract reconstruction between January 1992 and December 2014 at the Hôpital Universitaire des Enfants Reine Fabiola were included. We retrospectively collected and analysed demographic, echocardiographic, surgical, and follow-up data.

RESULTS

Of the 53 newborns who benefited from a right ventricular outflow tract reconstruction during the considered period, 30 received a Contegra 12 mm (mean age 15 ± 8 days), and 23 a small (9-14 mm) pulmonary homograft (mean age 10 ± 7 days). Overall mortality was 16.6% with Contegra versus 17.4% in the pulmonary homograft group (p = 0.98 log-rank). Operative morbidity and early re-operation for conduit failure were not significantly different between the two groups. Mean follow-up in this study is 121 ± 74 months. Survival free from re-operation was not different between the two groups (p = 0.15). Multivariable analysis showed that weight and significant early gradient were factors associated with anticipated conduit failure.

CONCLUSIONS

Contegra 12 mm is a valid alternative to small pulmonary homografts in a newborn patient population.

TRIAL REGISTRATION

NCT03348397.

Leaflet morphology classification of the Melody Transcatheter Pulmonary Valve

OBJECTIVE

We sought to describe the leaflet morphology variation in the Melody Transcatheter Pulmonary Valve (TPV) and evaluate associated outcomes. The Melody TPV is constructed from harvested bovine jugular venous valves which have been rigorously tested. Natural anatomic leaflet variations are seen in the Melody TPV but have not been evaluated.

DESIGN

A Melody TPV leaflet morphology classification system was devised after reviewing a subset of photographed and implanted TPVs. All images were blindly reviewed by implanters and classified. Midterm hemodynamic outcomes and complications of the Melody TPVs were compared by leaflet morphology.

RESULTS

Photographed Melody TPVs implanted between 2011 and 2016 (n = 62) were categorized into the following leaflet morphology types: A-symmetric trileaflet (47%); B-asymmetric trileaflet with a single small leaflet (32%); C-asymmetric trileaflet with a single large leaflet (16%); D-rudimentary leaflet with near bicuspid appearance (5%). Acceptable hemodynamic function at 6 months postimplantation was seen in 97.5% of valves. Over a median follow-up of 1.5 years (range 0-4.4 years), two TPVs (Type A) had > mild regurgitation. Nine TPVs developed complications (endocarditis, 3; stent fracture, 2; refractory arrhythmia, 1; conduit replacement, 2; death, 1), of which 6 required reintervention. There was no significant difference in outcomes based on Melody TPV leaflet morphology type.

CONCLUSIONS

The Melody TPV can be classified into one of four categories based on leaflet morphology. Study outcomes were not associated with leaflet morphology. Further documentation and evaluation of Melody TPV morphology may lead to better understanding of this technology.

Bioprosthetic pulmonary valve endocarditis: Incidence, risk factors, and clinical outcomes

BACKGROUND

Pulmonary valve replacement (PVR) is a common operation in patients with congenital heart disease (CHD). As survival with CHD improves, infective endocarditis (IE) is a growing complication after PVR. The aim of this study was to assess the incidence, risk factors, and clinical outcomes of IE after surgical PVR in patients with CHD at our institution.

METHODS

Retrospective analysis of all cases of surgical PVR performed at Children's Hospital of Wisconsin between 1975 and 2016 was performed. All cases of IE after PVR were identified and clinical and imaging data were obtained by review of medical records.

RESULTS

Out of 924 surgical PVRs, there were 19 (2%) cases of IE. The incidence of IE after surgical PVR was 333 cases per 100,000 person-years. The median age at diagnosis of IE was 21 years (range = 1.2-34 years) and the median time from PVR to diagnosis of IE was 9.4 years. The overall freedom from IE after PVR was 99.1%, 96.9%, and 93.4%, at 5, 10, and 15 years, respectively. There was no significant difference in freedom from IE based on valve type, including bovine jugular vein grafts. Patients with IE were more likely to have had a history of multiple PVRs, while length of follow-up after PVR, age at time of PVR, and gender were not significant risk factors. Eleven (58%) cases of IE required surgical intervention, while 8 (42%) were successfully treated with intravenous antibiotics alone. There were no deaths and no recurrences of IE after treatment.

CONCLUSION

The overall risk for IE after PVR is low. There was no association between age or type of pulmonary valve and risk of IE. The majority of cases require surgical intervention, but in general the outcomes of IE after PVR are good with low mortality and risk of recurrence.

Bovine Jugular Vein Conduit: A Mid- to Long-Term Institutional Review

Background:

Since 1999, we have used the bovine jugular vein conduit for right ventricular outflow tract reconstruction in infants and children. Herein, we review their mid- to long-term outcomes.

Methods:

Between 1999 and 2016, 315 bovine jugular vein conduits were implanted in 276 patients. Patients were grouped by age at bovine jugular vein conduit implant: group 1: 0 to 1 years (N = 65), group 2: one to ten years (N = 132), and group 3: older than ten years (N = 118). For survival and hemodynamic analysis, additional group stratification was done based on conduit size. Group small: 12 and 14 mm (N = 75), group medium: 16 and 18 mm (N = 84), and group large: 20 and 22 mm (N = 156).

Results:

Mean follow-up for groups 1, 2, and 3 was 4.0, 4.9, and 5.9 years, respectively. Early mortality was 9%, 0%, and 1% for groups 1, 2, and 3, respectively ( P < .001). Late mortality was 5%, 2%, and 2% for groups 1, 2, and 3, respectively ( P = .337). Group 1 had the lowest ten-year freedom from conduit failure at 13%, versus 53% and 69% for groups 2 and 3, respectively ( P < .001). A total of 21 (6.6%) patients developed endocarditis, 11 (3.5%) patients required reoperation, and 10 (3.2%) patients required antibiotic therapy alone.

Conclusions:

The bovine jugular vein conduit is a useful option for right ventricular outflow tract reconstruction given its easy implantability and acceptable midterm durability.

Infective Endocarditis After Melody Valve Implantation in the Pulmonary Position: A Systematic Review

Background

Infective endocarditis (IE) after transcatheter pulmonary valve implantation (TPVI) in dysfunctioning right ventricular outflow tract conduits has evoked growing concerns. We aimed to investigate the incidence and the natural history of IE after TPVI with the Melody valve through a systematic review of published data.

Methods and Results

PubMed, EMBASE, and Web of Science databases were systematically searched for articles published until March 2017, reporting on IE after TPVI with the Melody valve. Nine studies (including 851 patients and 2060 patient‐years of follow‐up) were included in the analysis of the incidence of IE. The cumulative incidence of IE ranged from 3.2% to 25.0%, whereas the annualized incidence rate ranged from 1.3% to 9.1% per patient‐year. The median (interquartile range) time from TPVI to the onset of IE was 18.0 (9.0–30.4) months (range, 1.0–72.0 months). The most common findings were positive blood culture (93%), fever (89%), and new, significant, and/or progressive right ventricular outflow tract obstruction (79%); vegetations were detectable on echocardiography in only 34% of cases. Of 69 patients with IE after TPVI, 6 (8.7%) died and 35 (52%) underwent surgical and/or transcatheter reintervention. Death or reintervention was more common in patients with new/significant right ventricular outflow tract obstruction (69% versus 33%; P=0.042) and in patients with non‐streptococcal IE (73% versus 30%; P=0.001).

Conclusions

The incidence of IE after implantation of a Melody valve is significant, at least over the first 3 years after TPVI, and varies considerably between the studies. Although surgical/percutaneous reintervention is a common consequence, some patients can be managed medically, especially those with streptococcal infection and no right ventricular outflow tract obstruction.

Application of a Simplified Hand-Sewn Trileaflet Valved Conduit in Right Ventricular Outflow Tract Reconstruction as an Alternative for Bovine Jugular Vein Graft: Single-Center Experience

The Bovine jugular vein (BJV) graft for right ventricular outflow tract reconstruction (RVOT) is limited applied due to possible graft failure. In this study, we reported the clinical application of simplified hand-sewn trileaflet valved conduit as an alternative for BJV graft. We retrospectively included 68 patients underwent 76 conduits implantation including 22 new simplified hand-sewn trileaflet valved conduits (Group A) and 54 BJV grafts (Group B). For patients in Group A, a hand-sewn trileaflet valved conduit with valves made of autologous pericardium or expanded polytetrafluoroethylene was applied. Baseline, perioperative, and outcomes were analyzed. No early mortality or perioperative complication occurred in Group A, while 2 patients died and 16 patients suffered from conduits failure due to conduits stenosis (n = 11), stenosis plus regurgitation (n = 3), and regurgitation alone (n = 2) in Group B. Freedom from BJV grafts failure within 1, 3, 5, and 7 years was 98.0%, 88.2%, 83.6% and 83.6% in Group A, and 98.0%, 85.8%, 76.8% and 62.1% in Group B. Endocarditis occurred in 9 patients in Group B, but not in Group A. Subsequent analysis showed that endocarditis is the only significant predictor of BJV grafts failure (odds ratio: 6.202, 95% confidence intervals 1.237∼31.108). The novel simplified hand-sewn trileaflet valved conduits seems to be associated with lower incidences of perioperative complication, graft failure, and early-phase mortality, as compared with conventional BJV grafts.

Decellularized Allografts for Right Ventricular Outflow Tract Reconstruction in Children

Objective:

Determine the midterm outcomes of decellularized allografts for right ventricular outflow tract (RVOT) reconstruction in children less than 12 years of age.

Methods:

The study included all consecutive patients submitted to RVOT reconstruction with decellularized allografts between June 2006 and June 2016. Besides clinical and echocardiographic control, 20 patients with more than five years of follow-up were evaluated with computed tomography (CT) scans to determine allograft diameters and calcium scores. Structural valve deterioration was defined as any peak gradient above 40 mm Hg and/or insufficiency of moderate or severe degree. Conduit failure was defined as the need for allograft reintervention.

Results:

There were 59 patients with a median age of six years (range = 0.01-12 years). The most common operation was the Ross procedure (34%). Mean clinical follow-up was 5.4 (2.8) years and was 94% complete. At eight years, only two patients needed a reintervention, with a 90.9% freedom from this event. Structural valve deterioration occurred in 13 patients, 5 due to stenosis and 8 due to insufficiency, with a freedom from structural valve deterioration due to any cause of 64.9% at eight years. Late CT scans demonstrated the absence or minimal calcification of the conduits.

Conclusions:

Decellularized allografts for RVOT reconstruction in children were associated with a low incidence of structural valve deterioration and conduit failure. Although these results still need to be confirmed in larger series and with longer follow-up, our data suggest favorable outcomes, at least in the first decade after the operation.

Transcatheter pulmonary valve implantation: valve technology and procedural outcome

PURPOSE OF REVIEW

Procedural technique and short-term outcomes of transcatheter pulmonary valve implantation (TPVI) have been widely described. The purpose of this article is to provide an update on current valve technology, and to focus on recent data surrounding TPVI in the dilated right ventricular outflow tract (RVOT), hybrid interventions, significant outcomes, and procedural costs.

RECENT FINDINGS

Transcatheter valve technology has expanded with current trials evaluating self-expandable valves that can be implanted in dilated RVOTs. Until those valves are widely available, hybrid techniques have been shown to offer a potential alternative in these patients, as well as in patients of small size. Although medium-term results of TPVI have shown 5-year freedom from reintervention or replacement of 76%, new data have underlined some concerns relating to bacterial endocarditis after the procedure. Procedural costs remain a concern, but vary greatly between institutions and healthcare systems.

SUMMARY

TPVI has emerged as one of the most innovative procedures in the treatment of patients with dysfunctional RVOT and pulmonary valves. Further device development is likely to expand the procedure to patients of smaller size and with complex, dilated RVOTs.

Mid- to long-term outcomes of bovine jugular vein conduit implantation in Chinese children

BACKGROUND

Bovine jugular vein (BJV) conduits are widely applied for surgical reconstruction of the right ventricular outflow tract (RVOT). However, relevant studies of valve failure rates and the related risk factors are limited in China. The aim of this study was to assess the BJV prognosis after medium- to long-term follow-up.

METHODS

Fifty-three hospital patients implanted with BJV conduits from January 2002 to December 2013 were recruited. Patient information and follow-up prognosis were reviewed retrospectively. Conduit stenosis and failure as well as endocarditis were diagnosed.

RESULTS

The total person years was 345.5, and the median follow-up time was 6.3 years. Early mortality occurred in two patients, and there was no late mortality. BJV conduit failure occurred in 15 patients (29.4%) due to severe stenosis (n=10), stenosis plus regurgitation (n=3), and regurgitation alone (n=2). The proportion of patients who were free of BJV conduit failure at 1, 3, 5, and 7 years was 98.0%, 85.8%, 76.8%, and 62.1%, respectively. There were nine cases of endocarditis (17.0%). Multivariate logistic regression analysis showed that endocarditis was a significant risk factor associated with BJV conduit failure (OR: 6.735; 95% CI: 1.348-33.647).

CONCLUSIONS

The durability of BJV conduits was suboptimal after a mid-term follow-up period. Endocarditis was found to be a significant risk factor that accelerates BJV conduit deterioration.

Mid-Term Outcomes in Patients with Congenitally Corrected Transposition of the Great Arteries: A Single Center Experience

BACKGROUND

Optimal management of patients with congenitally corrected transposition of the great arteries (ccTGA) is unclear. The goal of this study was to compare the outcomes in patients with ccTGA undergoing different management strategies.

STUDY DESIGN

Patients with ccTGA believed suitable for biventricular circulation, treated between 1995 and 2016, were included. The cohort was divided into 4 groups: systemic right ventricle (RV) (patients without surgical intervention or with a classic repair), anatomic repair, Fontan palliation, and patients receiving only a pulmonary artery band (PAB) or a shunt. Transplant-free survival from presentation was calculated for each group.

RESULTS

The cohort included 97 patients: 45 (46%) systemic RV, 26 (27%) anatomic repair, 9 (9%) Fontan, and 17 (18%) PAB/shunt. Median age at presentation was 2 months (range 0 days to 69 years) and median follow-up was 10 years (1 month to 28 years). At initial presentation, 10 (11%) patients had any RV dysfunction (8 mild, 2 severe), and 16 (18%) patients had moderate or severe tricuspid regurgitation (TR). During the study, 10 (10%) patients died, and 3 (3%) patients underwent transplantation. At last follow-up, 11 (11%) patients were in New York Heart Association class III/IV, 5 (5%) had moderate or severe systemic ventricle dysfunction, and 16 (16%) had moderate or severe systemic atrioventricular valve regurgitation. Transplant-free survivals at 10 years were 93%, 86%, 100%, and 79% for systemic RV, anatomic repair, Fontan palliation, and PAB/shunt, respectively (p = 0.33). On multivariate analysis, only systemic RV dysfunction was associated with a higher risk for death or transplant (p = 0.001).

CONCLUSIONS

Transplant-free survival in ccTGA appears to be similar between patients with a systemic RV, anatomic repair, and Fontan procedure. Systemic RV dysfunction is a risk factor for death and transplant.

Contegra 12 mm: How Long Can It Last?

Since the year 2000, we have used Contegra conduits for right ventricular outflow tract reconstruction in infants and newborns. Published reports of early and late results from multiple centers have included variable and inconsistent findings. Concerns about the durability of small conduits placed in younger infants have been expressed. We report an interesting experience with a 12-mm Contegra conduit that we explanted 16 years after implantation in the course of repair of truncus arteriosus (common arterial trunk) in an infant.