Tissue engineered vascular grafts transform into autologous neovessels capable of native function and growth.

Background: Tissue-engineered vascular grafts (TEVGs) have the potential to advance the surgical management of infants and children requiring congenital heart surgery by creating functional vascular conduits with growth capacity. Methods: Herein, we used an integrative computational-experimental approach to elucidate the natural history of neovessel formation in a large animal preclinical model; combining an in vitro accelerated degradation study with mechanical testing, large animal implantation studies with in vivo imaging and histology, and data-informed computational growth and remodeling models. Results: Our findings demonstrate that the structural integrity of the polymeric scaffold is lost over the first 26 weeks in vivo, while polymeric fragments persist for up to 52 weeks. Our models predict that early neotissue accumulation is driven primarily by inflammatory processes in response to the implanted polymeric scaffold, but that turnover becomes progressively mechano-mediated as the scaffold degrades. Using a lamb model, we confirm that early neotissue formation results primarily from the foreign body reaction induced by the scaffold, resulting in an early period of dynamic remodeling characterized by transient TEVG narrowing. As the scaffold degrades, mechano-mediated neotissue remodeling becomes dominant around 26 weeks. After the scaffold degrades completely, the resulting neovessel undergoes growth and remodeling that mimicks native vessel behavior, including biological growth capacity, further supported by fluid-structure interaction simulations providing detailed hemodynamic and wall stress information. Conclusions: These findings provide insights into TEVG remodeling, and have important implications for clinical use and future development of TEVGs for children with congenital heart disease.

Evaluation of Ductal Tissue in Coarctation of the Aorta Using X-Ray Phase-Contrast Tomography.

We assessed the histological accuracy of X-ray phase-contrast tomography (XPCT) and investigated three-dimensional (3D) ductal tissue distribution in coarctation of the aorta (CoA) specimens. We used nine CoA samples, including the aortic isthmus, ductus arteriosus (DA), and their confluences. 3D images were obtained using XPCT. After scanning, the samples were histologically evaluated using elastica van Gieson (EVG) staining and transcription factor AP-2 beta (TFAP2B) immunostaining. XPCT sectional images clearly depicted ductal tissue distribution as low-density areas. In comparison with EVG staining, the mass density of the aortic wall positively correlated with elastic fiber formation (R = 0.69, P < 0.001). TFAP2B expression was consistent with low-density area including intimal thickness on XPCT images. On 3D imaging, the distances from the DA insertion to the distal terminal of the ductal media and to the intima on the ductal side were 1.63 ± 0.22 mm and 2.70 ± 0.55 mm, respectively. In the short-axis view, the posterior extension of the ductal tissue into the aortic lumen was 79 ± 18% of the diameter of the descending aorta. In three specimens, the aortic wall was entirely occupied by ductal tissue. The ductal intima spread more distally and laterally than the ductal media. The contrast resolution of XPCT images was comparable to that of histological assessment. Based on the 3D images, we conclude that complete resection of intimal thickness, including the opposite side of the DA insertion, is required to eliminate residual ductal tissue and to prevent postoperative re-coarctation.

Improvement of a Novel Small-diameter Tissue-engineered Arterial Graft With Heparin Conjugation.

BACKGROUND: Small diameter (<6 mm), bioabsorbable, arterial, tissue-engineered vascular grafts (TEVGs) remain limited by thromboembolism. The objective of this study was to test whether heparin-eluting (HE) TEVGs prevent early thrombosis in a large animal model. METHODS: TEVGs were created with an outer poly-ε-caprolactone electrospun nanofiber layer, with a 15-µm average pore size and an inner layer composed of a 50:50 poly(L-lactide-co-ε-caprolactone) copolymer. Adult female sheep (n = 5) underwent bilateral carotid artery interposition grafting, with a control TEVG in 1 carotid artery and an HE TEVG in the contralateral position. Animals were followed for 8 weeks with weekly Duplex ultrasonography to monitor TEVG performance. RESULTS: All sheep survived to the designated endpoint. At 8 weeks all 5 HE TEVGs were patent. Three of 5 control TEVGs had early thrombotic occlusion at <1 week. More than 97% of heparin release occurred within the first 24 hours. Histologic evaluation of the HE TEVG displayed cellularity like a native carotid artery with no evidence of calcification. Significantly fewer platelets adhered to the HE TEVG than to the control TEVG (P < .001). CONCLUSIONS: This study suggests HE TEVGs prevent acute graft thrombosis. We hypothesize that the HE properties of the HE TEVG during vascular endothelialization is useful for maintaining TEVG patency. This technique may aid in the translation of small arterial TEVGs to the clinic.

Effect of Long-term Administration of Prostaglandin E1 on Morphologic Changes in Ductus Arteriosus.

BACKGROUND: To improve survival of patients with hypoplastic left heart syndrome, combination therapy with bilateral pulmonary artery banding and prostaglandin E1 (PGE1)-mediated ductal patency was developed as an alternative for high-risk neonates in Japan. However, the effect of long-term PGE1 administration on ductus arteriosus remains unclear. Synchrotron radiation-based X-ray phase-contrast tomography (XPCT) enables clear visualization of soft tissues at an approximate spatial resolution of 12.5 µm. We aimed to investigate morphologic changes in ductus arteriosus after long-term PGE1 infusion using XPCT. METHODS: Seventeen ductus arteriosus tissue samples from patients with hypoplastic left heart syndrome were obtained during the Norwood procedure. The median duration of lipo-prostaglandin E1 (lipo-PGE1) administration was 48 days (range, 3 to 123). Structural analysis of ductus arteriosus was performed and compared with conventional histologic analysis. RESULTS: The XPCT was successfully applied to quantitative measurements of ductal media. Significant correlation was found between the duration of lipo-PGE1 infusion and mass density of ductal media (R = 0.723, P = .001). The duration of lipo-PGE1 administration was positively correlated with elastic fiber staining (R = 0.799, P < .001) and negatively correlated with smooth muscle formation (R = -0.83, P < .001). No significant increase in intimal cushion formation was found after long-term lipo-PGE1 administration. Expression of ductus arteriosus dominant PGE2-receptor EP4 almost disappeared in specimens when lipo-PGE1 was administered over 3 days. CONCLUSIONS: Disorganized elastogenesis and little intimal cushion formation after long-term lipo-PGE1 administration suggest that ductus arteriosus remodeled to the elastic artery phenotype. Because EP4 was downregulated and ductus arteriosus exhibited elastic characteristics, the dosage of lipo-PGE1 might be decreased after a definite administration period.

Left Atrial Decompression by Minithoracotomy During Extracorporeal Life Support.

Extracorporeal membrane oxygenation through cervical cannulation is an established option for pediatric patients with acute cardiopulmonary failure. However, left-sided heart decompression is sometimes mandatory in patients with severe left ventricular dysfunction. This report describes a fast and less invasive technique for placing a left atrial cannula through a left anterior minithoracotomy approach. In 4 critically ill children, this minimally invasive technique provided satisfactory left-sided heart decompression, and this report describes a representative case.

Three Dimensional Visualization of Human Cardiac Conduction Tissue in Whole Heart Specimens by High-Resolution Phase-Contrast CT Imaging Using Synchrotron Radiation.

BACKGROUND: The feasibility of synchrotron radiation-based phase-contrast computed tomography (PCCT) for visualization of the atrioventricular (AV) conduction axis in human whole heart specimens was tested using four postmortem structurally normal newborn hearts obtained at autopsy. METHODS: A PCCT imaging system at the beamline BL20B2 in a SPring-8 synchrotron radiation facility was used. The PCCT imaging of the conduction system was performed with "virtual" slicing of the three-dimensional reconstructed images. For histological verification, specimens were cut into planes similar to the PCCT images, then cut into 5-µm serial sections and stained with Masson's trichrome. RESULTS: In PCCT images of all four of the whole hearts of newborns, the AV conduction axis was distinguished as a low-density structure, which was serially traceable from the compact node to the penetrating bundle within the central fibrous body, and to the branching bundle into the left and right bundle branches. This was verified by histological serial sectioning. CONCLUSION: This is the first demonstration that visualization of the AV conduction axis within human whole heart specimens is feasible with PCCT.

Left Subclavian Artery Perfusion During the Norwood Operation for Interrupted Aortic Arch With Aortic Atresia.

The combination of aortic atresia and interrupted aortic arch is a rare condition. We describe a case of Norwood operation for this defect, in which a collateral artery from the descending aorta supplied coronary perfusion. The devised cardiopulmonary bypass technique is discussed, in which the left subclavian artery perfusion was utilized in addition to the cannulation to the descending aorta to secure the cerebral perfusion.

Follow-Up of Persistent Tracheal Stenosis After Surgery for a Double Aortic Arch.

Persistent respiratory symptoms often occur after surgical repair of double aortic arch (DAA). Most often, symptoms are relatively mild and tend to be self-limited and improve with growth. Multidetector computed tomography (MDCT) imaging can be used to obtain needed anatomic information regarding the potential for extrinsic airway compression and is minimally invasive, safe, and readily available after surgery. We herein report the cases of two patients with persistent airway symptoms after surgical therapy for a double aortic arch. One of the patients eventually required aortopexy in order to achieve complete relief from recurrent symptoms of airway compression. In the other case, wheezing persisted following surgical division of the vascular ring, but it resolved over time without further intervention. In both cases, serial follow-up imaging with computed tomography scans was informative and helped guide management decisions.

Staged biventricular repair for absent aortic valve in a neonate.

Congenitally absent aortic valve is an extremely rare and fatal cardiac malformation. We report the case of a neonate with absent aortic valve, an interrupted aortic arch, and a normal-sized left ventricle. At age 9 hours, emergency aortic valve closure and a Norwood procedure were performed to maintain coronary circulation. The patient's postoperative course was complicated because of tracheomalacia and a severely dilated aorta that were treated with reduction aortoplasty at age 4 months. Finally, a staged Yasui procedure was performed at 26 months. To our knowledge, this is the first report of a successful biventricular repair for absent aortic valve.

A left anterior extrapleural approach to adjust right ventricle-pulmonary artery shunt flow using hemostatic clips after the Norwood operation.

Adjusting right ventricle-pulmonary artery shunt flow with placement of hemostatic clips in the Norwood operation is a useful technique for precise control of pulmonary blood flow in the acute postoperative period. This report describes our technique for optimizing right ventricle-pulmonary artery shunt flow with metal clips through a left anterior extrapleural approach, which can be performed safely and minimally invasively without sternal reopening. This procedure may decrease morbidity and contribute to long-term clinical improvement in patients undergoing the Norwood operation.

The left anterior extrapleural approach for innominate artery transection in a patient with tracheostomy and a neurological disorder.

Although innominate artery transection for innominate artery compression of the trachea is recently used for prevention of life-threatening complications (e.g. massive bleeding and obstructive apnoea) in patients with neurological disorders, pre-existing tracheostomy poses a risk of mediastinal infection with sternotomy. We successfully performed innominate artery transection on such a patient via the left anterior extrapleural approach without sternotomy after confirming the anatomical configuration on three-dimensional multidetector row computed tomography angiography.

Beating-heart surgery for hypoplastic left heart syndrome with coronary artery fistulas.

The presence of ventriculocoronary connections in patients with hypoplastic left heart syndrome and mitral stenosis-aortic atresia is a suggested risk factor for myocardial ischemia after surgical palliation. We describe a neonate with this anatomic variant of hypoplastic left heart syndrome who underwent a successful beating-heart Norwood operation, with continuous coronary perfusion. The ventricular condition could be visually confirmed during the procedure, and a postoperative echocardiogram showed preserved ventricular function. This technique is considered an effective option for minimizing myocardial damage in this patient subtype.

Pacing therapy in children.

BACKGROUND: The importance of ventricular pacing site in pediatric pacemaker therapy has gradually become recognized. We reviewed our experience with a left ventricular (LV)-prioritized pacing strategy. METHODS AND RESULTS: Between 2000 and 2012, 60 patients underwent 76 permanent pacemaker implantations. Eight of the 29 reoperations involved ventricular lead repositioning for pacing-induced ventricular dysfunction. Freedom from ventricular lead failure was 96.3%, 86.8%, and 81.0% at 1, 3, and 5 years, respectively. The independent predictors of ventricular lead failure were age (P=0.026) and peak minimal energy threshold within 6 months (P=0.035). At the measured points, redo bipolar, steroid-eluting leads had significantly better pacing properties than did redo non-steroid-eluting, screw-in leads (P=0.0009-0.03). Ventricular lead repositioning was effective in the 5 patients with systemic LV pacing, whereas its efficacy was inconsistent in patients with single-ventricle or systemic right ventricular (RV) pacing. At a median follow-up of 59 months, the 28 patients with LV pacing had preserved ventricular function (LV fraction shortening, 0.34±0.09). CONCLUSIONS: The outcome of this LV-prioritized pacing strategy in pediatric patients was excellent, demonstrating preserved ventricular function. Bipolar, steroid-eluting, epicardial pacing leads achieved good pacing properties, even in reoperation patients. In children with systemic LV and RV pacing-induced ventricular dysfunction, a conversion to LV apex pacing was an attractive alternative to cardiac resynchronization therapy.

False aneurysm with an aorto-superior vena cava fistula after replacement of the ascending aorta: report of a case.

A 58-year-old female presenting with congestive heart failure due to a fistula between an aortic false aneurysm and the superior vena cava (SVC) is described. She had a history of Takayasu's arteritis (TA) and she had undergone aortic valve and ascending aorta replacement and coronary artery bypass grafting 6 years before. The false aneurysm had occurred 1 year after the surgery, and she had been conservatively managed. The operation revealed that the cause of the false aneurysm was the detachment of the two proximal saphenous vein anastomoses to the ascending aortic graft. After the surgery, the patient made an uneventful recovery. A false aneurysm of the ascending aorta is one of the most serious complications after replacement of the ascending aorta for patients with TA (Miyata et al. in J Vasc Surg 27:438-445, 1998). We herein present the exceptional case of a fistula between an aortic false aneurysm and the SVC that occurred after ascending aorta graft replacement.

Double-patch repair by a bilateral ventriculotomy for postinfarction ventricular septal defect.

OBJECTIVES: Repair of a postinfarction ventricular septal defect (VSD) is a challenging procedure with a high risk of postoperative residual shunt and subsequent mortality. This retrospective study aimed to assess a modified infarct exclusion technique with a biventricular approach. METHODS: Nineteen consecutive patients who underwent the infarct exclusion procedure for VSD between 2002 and 2011 were reviewed. A biventricular approach (B group: 6 patients) and a left ventricular approach (L group: 13 patients) were studied by univariate analysis. RESULTS: The overall 30-day mortality was 15.8%, and was not different between the two groups (p=0.94). Postoperative residual shunt was not observed in the B group (p=0.21). The overall five-year survival rate was 79%, and there were no late deaths in the B group (p=0.14). CONCLUSION: The repair of postinfarction VSD can be safely performed by the infarct exclusion technique with a biventricular approach. This technique seems to reduce surgical mortality and prevents recurrence of the VSD.

Bilateral popliteal artery entrapment syndrome with asynchronous onset.

Popliteal artery entrapment syndrome is recognized as a cause of lower leg claudication in patients younger than 50 years of age. We report a rare case of a patient with bilateral popliteal artery entrapment who presented with the same symptom 11 years after his first experience of popliteal artery entrapment syndrome. On both occasions, the surgery was performed in a similar manner and the patient was free from symptoms after the surgery. Since the diagnosis of popliteal artery entrapment syndrome is difficult, early detection of popliteal artery entrapment syndrome is important to prevent its progression.