Effect of the ex situ physical and in situ chemical modification of bacterial nanocellulose on mechanical properties in the context of its potential applications in heart valve design.

Bacterial nanocellulose (BNC) is a promising material for heart valve prostheses. However, its low strength properties limit its applicability in cardiovascular surgery. To overcome these limitations, the mechanical properties of BNC can be improved through modifications. The aim of the research was to investigate the extent to which the mechanical properties of BNC can be altered by modifying its structure during its production and after synthesis. The study presents the results of various analyses, including tensile tests, nanoindentation tests, X-ray diffraction (XRD) tests, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy, conducted on BNC chemically modified in situ with hyaluronic acid (BNC/HA) and physically modified ex situ through a dehydration/rehydration process (BNC 25DR, BNC105DR, BNC FDR and BNC/HA 25DR, BNC/HA 105DR, BNC/HA FDR). The results demonstrate that both chemical and physical modifications can effectively shape the mechanical properties of BNC. These modifications induce changes in the crystalline structure, pore size and distribution, and residual stresses of BNC. Results show the effect of the crystalline structure of BNC on its mechanical properties. There is correlation between hardness and Young's modulus and Iα/Iß index for BNC/HA and between creep rate of BNC/HA, and Young's modulus for BNC vs Iα/Iß index.

Bacterial cellulose as a promising material for pulmonary valve prostheses: In vivo study in a sheep model.

OBJECTIVES: Currently, no consensus exists regarding the most durable prosthesis for pulmonary valve replacement. Bacterial cellulose is a resistant, nonbiodegradable, nonpyrogenic bioimplant with low hemolysis and clotting properties. We hypothesized that bacterial cellulose heart valve prostheses could be an attractive alternative for pulmonary valve replacement. METHODS: We conducted a large animal model experiment in three adult sheep. The animals underwent open-heart surgery and cardiopulmonary bypass for bacterial cellulose conduit implantation in the pulmonary position. The sheep were followed for seven months, and clinical and laboratory parameters were analyzed. Echocardiographic evaluations were performed at 3 and 7 months. After seven months, the sheep were sacrificed and an autopsy was performed. The explanted conduits were radiologically and histopathologically analyzed. RESULTS: All sheep survived the operation, showing good recovery and normal health status; no adverse events were noted during the 7-month postoperative follow-up. Interval laboratory findings were normal with no signs of hemolysis or infection. Echocardiographic analysis after 7 months revealed a normal mean pressure gradient with excellent cusp motion and coaptation; a trace of regurgitation was found in two sheep. X-ray analysis of the explanted conduits revealed no structural defects in the leaflets with minimal calcification. Histological examination showed slight thickening of the conduit by pannus formation. No material failure, no calcification inside the material, and only minor calcification extrinsic to the matrix were observed. CONCLUSIONS: This pilot study provides evidence that bacterial cellulose may be suitable for pulmonary valve prostheses and surgical pulmonary artery plasty. Further studies on the high pressure side of the left heart are needed.

In Vitro Study of a Stentless Aortic Bioprosthesis Made of Bacterial Cellulose.

PURPOSE: The paper present findings from an in vitro experimental study of a stentless human aortic bioprosthesis (HAB) made of bacterial cellulose (BC). Three variants of the basic model were designed and tested to identify the valve prosthesis with the best performance parameters. The modified models were made of BC, and the basic model of pericardium. METHODS: Each model (named V1, V2 and V3) was implanted into a 90 mm porcine aorta. Effective Orifice Area (EOA), rapid valve opening time (RVOT) and rapid valve closing time (RVCT) were determined. The flow resistance of each bioprosthesis model during the simulated heart systole, i.e. for the mean differential pressure (ΔP) at the time of full valve opening was measured. All experimental specimens were exposed to a mean blood pressure (MBP) of 90.5 ± 2.3 mmHg. RESULTS: The V3 model demonstrated the best performance. The index defining the maximum opening of the bioprosthesis during systole for models V1, V2 and V3 was 2.67 ± 0.59, 2.04 ± 0.23 and 2.85 ± 0.59 cm2, respectively. The mean flow rate through the V3 valve was 5.7 ± 1, 6.9 ± 0.7 and 8.9 ± 1.4 l/min for stroke volume (SV) of 65, 90 and 110 mL, respectively. The phase of immediate opening and closure for models V1, V2 and V3 was 8, 7 and 5% of the cycle duration, respectively. The mean flow resistance of the models was: 4.07 ± 2.1, 4.28 ± 2.51 and 5.6 ± 2.32 mmHg. CONCLUSIONS: The V3 model of the aortic valve prosthesis is the most effective. In vivo tests using BC as a structural material for this model are recommended. The response time of the V3 model to changed work conditions is comparable to that of a healthy human heart. The model functions as an aortic valve prosthesis in in vitro conditions.

Iatrogenic aortic arch injury after unsuccessful percutaneous tracheostomy.

Tracheostomy is a procedure that creates a direct opening to the airway through an incision in the anterior wall of the trachea. These days it is usually performed percutaneously as it is generally regarded as a safe procedure. We present the case of an unusual complication of aortic arch injury after percutaneous tracheostomy (PT) performed at an outside hospital. Major vascular injury was managed with sternotomy and direct aortic repair with a successful outcome. We believe PT should be performed under direct bronchoscopy visualization to limit any possible complications. Intensivists should be aware of this extremely rare complication of PT, which requires emergency cardiac surgery intervention and a team effort for appropriate management.

Liquid biopsy for minimally invasive heart transplant monitoring: a pilot study.

BACKGROUND: Heart transplantation allows for a long-term management of patients with end-stage heart failure. After the surgery, organ rejection is monitored with endomyocardial biopsy, which is an invasive, but not always informative procedure. Therefore, there is a pressing need for a new, safe, yet reliable, diagnostic method. Here, we present a pilot study confronting liquid biopsy based on donor-specific cell-free DNA with the protocol endomyocardial biopsy. METHODS: The study was performed on 21 blood samples matched with endomyocardial biopsy (graded according to acute cellular rejection scale) from nine patients after heart transplantation. Genotyping was performed on genomic DNA from donors and recipients for 10 single-nucleotide polymorphisms (SNPs). Cell-free DNA isolated from plasma was analysed with digital droplet PCR to detect donor-specific alleles. RESULTS: From 21 analysed endomyocardial biopsies, 4 were graded as 0R and 17 as 1R. Liquid biopsy was successfully performed in each sample for all informative SNPs (median of 3 per patient). We observed a high homogeneity of the results between SNPs in each sample (interclass correlation coefficient of >0.9). CONCLUSIONS: There is a undeniable need for an alternative, non-invasive diagnostic procedure of early transplant rejection and investigation of donor-derived cell-free DNA seems to be the promising choice. The very high sensitivity is particularly enticing to consider liquid biopsy as a potential screening tool. Its minimal invasiveness may allow for more frequent examination and, thus, tighter monitoring. The reliable assessment of its clinical utility requires an adequately powered and properly designed multicentre study.

Assessment of the usefulness of bacterial cellulose produced by Gluconacetobacter xylinus E25 as a new biological implant.

Bionanocellulose (BNC) is a clear polymer produced by the bacterium Gluconacetobacter xylinus. In our current study, "Research on the use of bacterial nanocellulose (BNC) in regenerative medicine as a function of the biological implants in cardiac and vascular surgery", we carried out material analysis, biochemical analysis, in vitro tests and in vivo animal model testing. In stage 1 of the project, we carried out physical and biological tests of BNC. This allowed us to modify subsequent samples of bacterial bionanocellulose. Finally, we obtained a sample that was accepted for testing on an animal model. That sample we define BNC1. Patches of BNC1 were then implanted into pigs' vessel walls. During the surgical procedures, we evaluated the technical aspects of sewing in the bioimplant, paying special attention to bleeding control and tightness of the suture line and the BNC1 bioimplant itself. We carried out studies evaluating the reaction of an animal body to an implantation of BNC1 into the circulatory system, including the general and local inflammatory reaction to the bioimplant. These studies allowed us to document the potential usefulness of BNC as a biological implant of the circulatory system and allowed for additional modifications of the BNC to improve the properties of this new implantable biological material.

First uses of HAART 300 rings for aortic valve repair in Poland - 4 case studies.

INTRODUCTION: Aortic valve reconstructions using geometric annuloplasty rings HAART 300/200 open new era in aortic valve surgery. The HAART technology resizes, reshapes, stabilizes and simplifies aortic valve repair. The HAART aortic repair rings are designed to be implanted directly into aortic annulus (under aortic valve leaflets). AIM: We present first in Poland 4 cases of aortic valve reconstructions using geometric annuloplasty rings HAART 300. MATERIAL AND METHODS: Two patients had type IA aortic insufficiency (due to El-Khoury classification) - they were treated by HAART 300 ring insertion and ascending aorta prosthesis implantation. Third patient, Marfan with type IB aortic insufficiency was repaired by HAART 300 ring implantation followed by remodeling (Yacoub) procedure. Fourth patient with type II aortic insufficiency (due to RCC prolapse) was repaired by HAART 300 implantation and cusp plication. RESULTS: All patients shows good results on 6 months postoperative 3D TTE examinations. CONCLUSIONS: Presented technique is reproducible and simplify aortic valve reconstructions.

Incidence- and mortality-related risk factors of acute kidney injury requiring hemofiltration treatment in patients undergoing cardiac surgery: a single-center 6-year experience.

OBJECTIVE: To evaluate the incidence and mortality risk factors of severe acute kidney injury (AKI) requiring hemofiltration treatment after cardiac surgery. DESIGN: A single-center, retrospective, case-control study. SETTING: A post-cardiac-surgical intensive care unit at a university hospital. PARTICIPANTS: Nine thousand two hundred twenty-two consecutive adult cardiac surgical patients, among whom 107 developed severe AKI. INTERVENTIONS: Continuous venovenous hemofiltration. MEASUREMENTS AND MAIN RESULTS: The overall incidence of severe AKI was 1.2%, but it differed with the type of surgical procedure including coronary artery bypass graft surgery, 0.4%; heart valves, 1.7%; aorta surgery, 5.4%; ventricle septum rupture, 52.6%; and other, 6.5%. From 6 predictors of 30-day mortality identified by univariate logistic regression (age, preoperative serum creatinine, New York Heart Association class, resternotomy, postoperative myocardial infarction, and postoperative use of intra-aortic balloon pump [IABP]), only the need for the postoperative use of IABP (odds ratio, 2.9; p = 0.01) and resternotomy (odds ratio, 3.4; p = 0.005) proved stable in multivariate analysis. Kaplan-Meier analysis identified the following overall mortality risk factors: age (p = 0.03), New York Heart Association class ≥II (p = 0.0004), resternotomy (p = 0.02), postoperative myocardial infarction (p = 0.01), and IABP (p = 0.03). CONCLUSIONS: The risk of developing severe AKI depended on the type of cardiac surgical procedure. Thirty-day mortality was associated with severe perioperative circulation impairment or bleeding, but overall long-term mortality was additionally predicted by age, postoperative myocardial infarct, and preoperative circulation status.

[Side effects of specific immunotherapy in patients with hymenoptera venom allergy]. / Objawy niepozadane podczas immunoterapii swoistej u chorych z alergia na jady owadów blonkoskrzydlych.

The aim of this study was to estimate safety of specific immunotherapy to insects' venom. The frequency of side effects was compared in two groups of patients: subjects with hypersensitivity to insects' venom only and patients with allergy to other allergens. In the examined group of 32 patients with Hymenoptera venoms allergy skin prick tests with common aeroallergens were performed in 30 subjects. In 18 patients (60%) at least one test was positive. In 23 patients (71.9%) immunotherapy with Hymenoptera venom was connected with side effects observed just after administration of vaccine. They were mainly local reactions (itching, redness and oedema). In 6 patients late reactions were observed. No correlation has been found between frequency of side effects of immunotherapy and positive results of skin prick tests. However systemic reactions were revealed only in the group of patients with at least one positive result of skin prick tests.