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Objective Upper airway malacia highly complicates the treatment of benign laryngotracheal stenosis, and no ideal option is available to date. We here explore the use of extraluminal biodegradable splints in an animal model of long-segment anterior tracheomalacia (TM). We show the efficacy, as well as the tissue tolerance, of a custom-made biodegradable extraluminal device surgically inserted around the trachea. Study Design Preclinical animal study. Methods Anterior TM was induced in rabbits through an anterior neck approach by removing eight consecutive anterior tracheal rings without damaging the underlying mucosa. Malacia was corrected during the same surgery by pexy sutures, suspending the tracheal mucosa to an experimental biodegradable device. Symptoms, survival, and tissue reaction were compared to healthy and sham surgery controls. Results The model induced death by respiratory failure within minutes. Ten animals received the experimental treatment, and those who survived the perioperative period remained asymptomatic with a maximum follow-up of 221 days. Histological studies at programmed euthanasia showed complete degradation of the prosthesis, with significant remnant fibrosis around the trachea. However, the tracheal stiffness of test segments was comparatively less than that of control segments. Conclusion Extraluminal biodegradable splints rescued animals with a condition otherwise incompatible with life. It was well tolerated, leaving peritracheal fibrosis that was not as stiff as normal trachea. The external tracheal stiffening was sufficient for the test animals to live through the phase of severe acute hypercollapsibility. This represents a valid option to help pediatric patients with laryngotracheal stenosis and associated cartilaginous airway malacia. Level of Evidence NA. Laryngoscope, 2017

OBJECTIVES The aim was to determine 3-dimensional (3D) geometrical deformation of the aortic root (AoR) following the David procedure in order to evaluate local haemodynamical conditions of individual AoR elements. METHODS In the experimental set-up, the David procedure was performed on 10 domestic pigs. Data were compared with the measurements obtained in 10 native AoRs. In each AoR, six high-resolution ultrasonometric crystals (200 Hz) were implanted, being positioned at each commissure and at the AoR base. 3D geometrical deformation of the AoR, torsion and tilt angle was determined. Computed fluid dynamics (CFD) simulation analysis was used to evaluate local pressure, flow and shear stress. RESULTS In David AoRs, the tilt angle was maximal at a peak ejection of 25.9 ± 1.49° and minimal at the end of isovolemic contraction at 23.5 ± 0.80°. David root rotation was maximal at a peak ejection of 27.93 ± 1.54° and minimal at the end of the isovolemic contraction at 25.7 ± 1.32°. In the native AoR, the opposite was observed. Here, the tilt and rotation angle were maximal at the end of isovolemic contraction (17.25 ± 0.68° and 19.71 ± 0.73°) and decreased to its minimal values at peak ejections (14.1 ± 0.62° and 16.33 ± 0.47°). In David AoR, high pressure (>140 mmHg) combined with low-to-moderate shear stress (0-40 Pa) was found at the leaflet body from the beginning of isovolemic contraction till the opening of the aortic valve. Similar high pressure (>140 mmHg) and shear stress (0-40 Pa) were found in the period from aortic valve closure till the beginning of the isovolemic contraction. In native AoRs, high pressure (>95 mmHg) was conjoined with low-to-moderate shear stress (0-30 Pa) at the leaflets and was registered at the end of isovolemic contraction. CONCLUSIONS The David AoR is haemodynamically less favourable when compared with the native AoR. During almost two-thirds of the time period of the cardiac cycle, AoR elements are exposed to high pressure and low shear stress. In contrast, in native AoRs, similar conditions were present only during the short period of isovolemic contraction.

Fibrin glue products and collagen patches are frequently used as a sealing product, preventing surgical side bleedings. This is especially true in the field of cardiovascular surgery, where increasing numbers of patients are being operated with antiplatelet and anticoagulation therapy. The aim of this report was, in an in vitro hemodynamic setting, to examine the sealant properties of the TachoSil (Nycomed Pharma, Linz, Austria) patch. Burst pressure and normal force of 15 TachoSil sealed defects were measured. This was determined in a closed hydraulic system. Mean burst pressure load for a 5-mm defect was 69+/-11.4 mmHg; for a 7-mm defect was 63+/-16 mmHg; and, 62+/-16 mmHg for the defect with a diameter of 10 mm (P>0.05). The mean calculated normal force was as follows: 0.91+/-0.15 N for the 5 mm defect, 6.5+/-1.6 N for the 7 mm, and 8.1+/-0.75 N for the 10 mm defect. The TachoSil patch has the capability to seal small defects. However, at the larger defects the seal character was significantly reduced. These results suggest that the device may be a good alternative for hemostasis for small defects. The capacity to curtail or stop hemorrhage at the larger defects is unlikely.

OBJECTIVES: The reconstruction of the right ventricular outflow tract (RVOT) with valved conduits remains a challenge. The reoperation rate at 5 years can be as high as 25% and depends on age, type of conduit, conduit diameter and principal heart malformation. The aim of this study is to provide a bench model with computer fluid dynamics to analyse the haemodynamics of the RVOT, pulmonary artery, its bifurcation, and left and right pulmonary arteries that in the future may serve as a tool for analysis and prediction of outcome following RVOT reconstruction. METHODS: Pressure, flow and diameter at the RVOT, pulmonary artery, bifurcation of the pulmonary artery, and left and right pulmonary arteries were measured in five normal pigs with a mean weight of 24.6 ± 0.89 kg. Data obtained were used for a 3D computer fluiddynamics simulation of flow conditions, focusing on the pressure, flow and shear stress profile of the pulmonary trunk to the level of the left and right pulmonary arteries. RESULTS: Three inlet steady flow profiles were obtained at 0.2, 0.29 and 0.36 m/s that correspond to the flow rates of 1.5, 2.0 and 2.5 l/min flow at the RVOT. The flow velocity profile was constant at the RVOT down to the bifurcation and decreased at the left and right pulmonary arteries. In all three inlet velocity profiles, low sheer stress and low-velocity areas were detected along the left wall of the pulmonary artery, at the pulmonary artery bifurcation and at the ostia of both pulmonary arteries. CONCLUSIONS: This computed fluid real-time model provides us with a realistic picture of fluid dynamics in the pulmonary tract area. Deep shear stress areas correspond to a turbulent flow profile that is a predictive factor for the development of vessel wall arteriosclerosis. We believe that this bench model may be a useful tool for further evaluation of RVOT pathology following surgical reconstructions.

Une membrane biorésorbable, composée de polysaccharides (hyaluronate de sodium et carboxymethylcellulose), a déjà été employée avec succès dans la prévention des adhérences péritonéales. Son efficacité dans la prévention des adhérences péricardiques est testée. Deux groupes de six porcs chacun (poids moyen 72 +/- 8kg) ont été choisis pour l'expérience. Dans le groupe "membrane", après l'excision d'une partie du péricarde, la région du ventricule gauche exposée est divisée en deux aires: l'aire A où six points de Prolène sont suturés et l'aire B laissée intacte. La membrane est appliquée sur ces deux aires ainsi que sur les régions adjacentes recouvertes de péricarde (aire C). Dans le groupe "contrôle", la même intervention est effectuée, mais sans membrane. Les animaux sont sacrifiés un mois plus tard. Le status adhérentiel des différentes aires ainsi que la visibilité des vaisseaux épicardiques sont évalués au moyen d'échelles de sévérité allant de 0 à 3 pour les adhérences et de 0 à 2 pour la visibilité. La différence entre les 2 groupes est considérée comme significative si p < 0.05. Le score d'adhérence de l'aire A est de 1.7 +/- 0.5 dans le groupe membrane versus 2.5 +/- 0.5 dans le groupe contrôle (p = 0.02) et le score de visibilité est de 1.3 +/- 0.8 versus 2 +/- 0 respectivement (n.s.). Pour l'aire B, le score d'adhérence est de 1 +/- 0 dans le groupe membrane versus 2 +/- 0.6 dans le groupe contrôle (p = 0.03) et le score de visibilité est de 0.7 +/- 0.5 versus 2 +/- 0 respectivement (p = 0.001). Enfin pour l'aire C, le score d'adhérence est de 1 +/- 0 dans les deux groupes et le score de visibilité est de 0.7 +/- 0.4 dans le groupe membrane versus 0.5 +/- 0.5 dans le groupe contrôle (n.s.). Dans ce modèle animal, le rôle de la membrane biorésorbable dans la prévention des adhérences péricardiques se limite aux régions non recouvertes de péricarde et dépourvues de matériel étranger. La présence de corps étranger neutralise son effet.

Despite an overall improvement in cardiopulmonary bypass (CPB) technology and materials, air emboli still occur. The latest generation membrane oxygenator from Bentley Laboratories, the SpiralGold™, was tested ex vivo for its air handling ability. The study was conducted on four calves. Bolus amounts of air of 10, 15 and 20 cm3 were each injected three times, upstream of the oxygenator and a bubble detector located directly downstream. The amount of bubbles was measured semiquantitatively on a 10 unit scale (U = one semiquantitative unit). The animals were killed 10 days after the CPB. When 10 cm3 of air was injected, no bubbles were detected. With 15 and 20 cm3, respectively, 1 ± 1.5 and 5 ± 3.3 U of bubbles were detected. Despite a total of 135 cm3 of air injected as large bolus amounts, all the animals survived without any obvious neurological deficit secondary to air bubble manipulation. In conclusion, the Spiral Gold™ oxygenator per se can reliably trap an air bolus of up to 10 cm3. This feature should be taken into account when choosing an oxygenator, as it offers an additional barrier to air bubbles in the CPB circuit.

Objectives The aim was to evaluate the impact of the aortic valve reimplantation (David) and of the aortic root (AoR) remodelling (Yacoub) on the AoR haemodynamics. Methods In an experimental setup where the clinical scenario of Yacoub, ( n = 5, domestic pig) and of David ( n = 5, domestic pig) procedure was performed in each AoR, six high-fidelity (200 Hz) sonomicrometric crystals were implanted. Crystals were positioned at three commissures with their projection at the root base. In post-measurement processing 3D deformation of both AoR was determined and used for computed fluid dynamic modelling in order to evaluate pressure, velocity and shear stress profiles. Results In David AoR: high pressure (> 150 mmHg) and low to moderate shear stress (0-30 Pa) were found from the period of isovolemic contraction to the closure of the aortic valve. At mid diastole pressure augmentation (> 120 mmHg) a low shear stress (0-10 Pa) was registered at the leaflets, three commissures, and intervalvular triangles. In Yacoub AoR: high pressure (110-130 mmHg) with moderate low shear stress (0-30 Pa) was only registered at isovolemic contraction. Conclusions The results show that haemodynamic conditions following a David procedure have a less favourable pattern as compared to a Yacoub AoR. In David AoR, high pressure and low shear stress are present during 2/3 of the cardiac cycle, whereas in Yacoub root, these conditions are present only for a short period of isovolemic contraction.

The aim of this report is to address the benefits of the minimal invasive venous drainage in a pediatric cardio surgical scenario. Juvenile bovine experiments (67.4+/-11 kg) were performed. The right atrium was cannulated in a trans-jugular way by using the self-expandable (Smart Stat, 12/20F, 430 mm) venous cannula (Smartcannula LLC, Lausanne, Switzerland) vs. a 14F 250 mm (Polystan Lighthouse) standard pediatric venous cannula. Establishing the cardiopulmonary bypass (CPB), the blood flows were assessed for 20 mmHg, 30 mmHg and 40 mmHg of driving pressure. Venous drainage (flow in l/min) at 20 mmHg, 30 mmHg, and 40 mmHg drainage load was 0.26+/-0.1, 0.35+/-0.2 and 0.28+/-0.08 for the 14F standard vs. 1.31+/-0.22, 1.35+/-0.24 and 1.9+/-0.2 for the Smart Stat 12/20F cannula. The 43 cm self-expanding 12/20F Smartcannula outperforms the 14F standard cannula. The results described herein allow us to conclude that usage of the self-expanding Smartcannula also in the pediatric patients improves the flow and the drainage capacity, avoiding the insufficient and excessive drainage. We believe that similar results may be expected in the clinical settings.