Aspirin Responsiveness in a Cohort of Pediatric Patients with Right Ventricle to Pulmonary Artery Conduits and Transcatheter Valve Replacement Systems

The aim of this study was to determine the rate of aspirin responsiveness in a cohort of pediatric patients with in situ xenograft valved right ventricle to pulmonary artery (RV-PA) conduits and/or transcatheter valve replacements (TVR). Aspirin is routinely prescribed to these patients. Optimizing anti-platelet therapy could promote valve longevity and reduce the risk of infective endocarditis in this at-risk group. This was a prospective, observational study. Patients were recruited from both ward and outpatient settings. Patients were eligible if under 18 years and taking aspirin. Non-response to aspirin was defined as > 20% platelet aggregation using light transmission platelet aggregometry (LTA) and < 50% platelet inhibition by thromboelastography with platelet mapping (TEGPM). Participants were invited to provide a confirmatory sample in cases of aspirin resistance and dose adjustments were made. Thirty patients participated. Median age was 9 years (2 months to 18 years). The majority (93%) had complex right ventricular outflow tract pathology. 13 (43%) had an RV-PA conduit and 24 (80%) had a TVR, with valve situated in conduit in 7 (23%) cases. Rate of aspirin non-response on initial testing was 23% (n = 7/30) with median LTA 74.55% (60-76%) and TEG 13.25% (0-44%) in non-responders. Non-responders were more likely to be under 1 year. Two patients required dose increases and one patient non-adherence to dose was identified. Four patients on repeat testing were responsive to aspirin by laboratory tests. The rate of aspirin non-response on laboratory testing in this cohort of patients was 23% and resulted in therapeutic intervention in 10%.

Pediatric tri-tube valved conduits made from fibroblast-produced extracellular matrix evaluated over 52 weeks in growing lambs

There is a need for replacement heart valves that can grow with children. We fabricated tubes of fibroblast-derived collagenous matrix that have been shown to regenerate and grow as a pulmonary artery replacement in lambs and implemented a design for a valved conduit consisting of three tubes sewn together. Seven lambs were implanted with tri-tube valved conduits in sequential cohorts and compared to bioprosthetic conduits. Valves implanted into the pulmonary artery of two lambs of the first cohort of four animals functioned with mild regurgitation and systolic pressure drops <10 mmHg up to 52 weeks after implantation, during which the valve diameter increased from 19 mm to a physiologically normal ~25 mm. In a second cohort, the valve design was modified to include an additional tube, creating a sleeve around the tri-tube valve to counteract faster root growth relative to the leaflets. Two valves exhibited trivial-to-mild regurgitation at 52 weeks with similar diameter increases to ~25 mm and systolic pressure drops of <5 mmHg, whereas the third valve showed similar findings until moderate regurgitation was observed at 52 weeks, correlating to hyperincrease in the valve diameter. In all explanted valves, the leaflets contained interstitial cells and an endothelium progressing from the base of the leaflets and remained thin and pliable with sparse, punctate microcalcifications. The tri-tube valves demonstrated reduced calcification and improved hemodynamic function compared to clinically used pediatric bioprosthetic valves tested in the same model. This tri-tube valved conduit has potential for long-term valve growth in children.

Four right ventricle to pulmonary artery conduit types

OBJECTIVE

The most durable valved right ventricle to pulmonary artery conduit for the repair of congenital heart defects in patients of different ages, sizes, and anatomic substrate remains uncertain.

METHODS

We performed a retrospective analysis of 4 common right ventricle to pulmonary artery conduits used in a single institution over 30 years, using univariable and multivariable models of time-to-failure to analyse freedom from conduit dysfunction, reintervention, and replacement.

RESULTS

Between 1988 and 2018, 959 right ventricle to pulmonary artery conduits were implanted: 333 aortic homografts, 227 pulmonary homografts, 227 composite porcine valve conduits, and 172 bovine jugular vein conduits. Patients weighed 1.6 to 98.3 kg (median 15.3 kg), and median duration of follow-up was 11.4 years, with 505 (52.2%) conduits developing dysfunction, 165 (17.2%) requiring catheter intervention, and 415 (43.2%) being replaced. Greater patient weight, conduit z-score, type and position, as well as catheter intervention were predictors of freedom from replacement. Multivariable analysis demonstrated inferior durability for smaller composite porcine valve conduits, with excellent durability for larger diameter conduits of the same type. Bovine jugular vein conduit longevity was inferior to that of homografts in all but the smallest patients. Freedom from dysfunction at 8 years was 60.7% for aortic homografts, 72% for pulmonary homografts, 51.2% for composite porcine valve conduits, and 41.3% for bovine jugular vein conduits. Judicious oversizing of the conduit improved conduit durability in all patients, but to the greatest extent in patients weighing 5 to 20 kg.

CONCLUSIONS

Pulmonary and aortic homografts had greater durability than xenograft conduits, particularly in patients weighing 5 to 20 kg. Judicious oversizing was the most significant surgeon-modifiable factor affecting conduit longevity.

Long-term results after the Ross procedure with the decellularized AutoTissue Matrix P® bioprosthesis used for pulmonary valve replacement

OBJECTIVES

Since 1967, the Ross procedure has been performed to treat aortic valve disease using homografts for pulmonary valve replacement. The decellularized Matrix P® prosthesis was developed to overcome (some) limitations of homografts. Until now, the long-term outcome data have been unavailable.

METHODS

Between 2002 and 2010, the Ross procedures using the Matrix P prosthesis were performed in 492 adult patients (mean age 57.2 ± 10.6 years, range 21-73 years) at our institution. Patient data were prospectively collected and analysed (3617.3 patient-years, mean follow-up 7.7  ±  4.3 years). Completeness of follow-up at 1, 5 and 10 years was 98.4%, 94.5% and 91.0%, respectively.

RESULTS

Hospital mortality was 3.9% (n  = 19). During follow-up, 121 patients died resulting in a survival rate at 5, 10 and 12.5 years of 82.8  ±  1.7%, 70.4  ±  2.3% and 62.4  ±  2.9%, respectively. Echocardiography revealed a high incidence of relevant dysfunction of the Matrix P prosthesis and subsequent right ventricular failure. Primary reoperation/reintervention was necessary for 150 Matrix P and 48 autografts. Freedom from pulmonary valve reoperation at 5, 10 and 12.5 years was 76.2  ±  2.1%, 58.6  ±  2.9% and 53.4  ±  3.4%, respectively. The autograft function and the left ventricular function showed similar results as previously reported with a freedom from autograft reoperation at 5, 10 and 12.5 years of 91.8  ±  1.4%, 86.1  ±  2.0% and 86.1  ±  2.0%, respectively.

CONCLUSIONS

The Matrix P prosthesis used for the right ventricular outflow tract reconstruction in the Ross procedure showed unfavourable long-term echocardiographic results with a high rate of reoperation/reintervention for structural pulmonary valve failure. As a consequence, long-term survival of this patient cohort was impaired. Based on these findings, the use of the Matrix P prosthesis for pulmonary valve replacement for Ross procedures in adults should not be recommended.

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.

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.

Durability of down-sized homografts for the reconstruction of the right ventricular outflow tract

OBJECTIVES

Small-sized homografts are rare but may be required for the reconstruction of the right ventricular outflow tract (RVOT). Down-sizing adult-sized homografts can be an option to overcome the shortage of availability.

METHODS

Since 1994, we have been down-sizing adult-sized homografts by excising one cusp. The aim of the study was to analyse the durability of down-sized homografts and compare it with small-sized homografts in a paediatric population. All patients below a body weight of 14 kg were included in the study. The end-point of the study was homograft failure.

RESULTS

A total of 152 patients met the inclusion criteria of the study, of which 82 patients (54%) received a down-sized homograft. The median age was 17.1 (0.3-64.8) months and the mean weight 8.4 ± 3.4 kg. Fifty-eight patients (38%) were under 1 year and 10 (6.5%) under 1 month of age at the time of homograft implantation. The mean homograft size of the whole study population was 14.7 ± 2.5 mm and the mean z-score was 1.6 ± 0.9. The median follow-up time was 10 (0.03-19.7) years. Early mortality after homograft implantation was 5% (n = 8), 4 of these patients had received a down-sized homograft. The study population comprised early survivors, that is, 144 patients. During follow-up, a total of 46 homografts failed, 23 in each group, after a mean time of 5.7 ± 4.2 years. Freedom from homograft failure was 94.6 ± 2.6, 87.2 ± 4 and 68.6 ± 6.6% for down-sized homografts and 95.2 ± 2.7, 78.7 ± 5.5 and 61 ± 7% for small-sized homografts at 1, 5 and 10 years, respectively (P = 0.3). Risk factors for homograft failure in the multivariable analysis were a homograft z-score of <1 and age below 1 year at the time of implantation (P = 0.02).

CONCLUSION

Down-sized homografts demonstrated a durability similar to that of small-sized homografts. Therefore, down-sizing adult-sized homografts by creating a bicuspid valve to fit into the corresponding RVOT in children with congenital heart defects is an excellent method to overcome the shortage of small-sized homografts.

Mosaic tissue-engineered porcine pulmonary artery valved conduit: long-term follow-up after implantation in an ovine model

OBJECTIVES

To determine the effects of implanting a novel mosaic tissue-engineered porcine pulmonary artery valved conduit into the right ventricular outflow tract of sheep at a long-term follow-up.

METHODS

The designed mosaic tissue-engineered porcine pulmonary artery valved conduits were implanted between the right ventricular outflow tract and distal pulmonary artery in sheep using the off-pump method. The sheep weight, conduit diameter, pulmonary valve annular diameter, left ventricular end-diastolic diameter, calcification and regurgitation of the pulmonary valve were measured preoperatively and at 6 and 12 months postoperatively. Macroscopic observation, ultrastructural analysis, endothelialization and detection of calcium content were performed after sacrificing the sheep at 12 months after surgery.

RESULTS

The average sheep weight at 12 months after surgery was significantly higher than that preoperatively (P <0.05), indicating that the sheep continued to grow well. The transplanted conduit showed unobstructed blood flow, soft walls and a smooth inner wall, but no ectasia or stenosis. The valve of the conduit was partially stiff, able to open and close and mild-to-medium regurgitation was present. The conduit diameter, pulmonary valve annular diameter and the left ventricular end-diastolic diameter were each significantly increased (P <0.05). Haematoxylin-eosin staining and scanning electron microscopy revealed regularly arranged cells with slight inflammatory cell infiltration and a clear, fibrous texture. Immunohistochemical staining indicated that endothelial cell marker CD31-positive cells had formed a continuous film-like structure on the inner wall of the conduit. Scattered smooth muscle actin-positive cells were found in the middle layer of the conduit.

CONCLUSIONS

The mosaic tissue-engineered porcine pulmonary artery valved conduit demonstrated good biocompatibility, did not cause an immune rejection response, contributed to endothelial coverage and has the potential to adapt to the needs of the growth and development of the body.