Design of a fully intraureteral stent and proof-of-concept in vivo evaluation.

Background: Ureteral stents are employed regularly to facilitate urine drainage and ureteral healing in a wide variety of endourological procedures, associated mainly with ureteral stone obstruction. However, stent use frequently impairs patient quality of life, which is generally attributed to the presence of anchoring stent curls in the bladder and/or kidney. The purpose of this study was to examine the potential effectiveness and safety of a newly designed, fully intraureteral stent, in an initial proof-of-concept in vivo evaluation. Methods: "Yoticurl" stents were synthesized from copolymeric, commercially-available ureteral stents. A first test to confirm the intended expansion of the spiral curls in a ureter was performed on a pig cadaver. Subsequently, a preliminary in vivo evaluation in a single pig model was completed to test stent viability, over a period of 25 days. Two stents were inserted to fully intraureteral positions into the two ureters, by standard human endourological procedure. Daily observational checks of the pig, and regular radiographic analyses were performed; the animal was then euthanized and examined by explorative laparotomy, followed by histological analysis of kidney, ureter and bladder tissue samples. Results: The pig displayed normal activity, appetite and sleep patterns, and radiography indicated free flow of urine, and no significant stent migration nor anatomical abnormalities. Subsequent histology found only mild inflammation in the ureter. Conclusions: The innovative stent design tested here, if ultimately proven safe and effective for human use, may offer an alternative to currently available stents for multiple indications.

Isolation of pulmonary veins using a thermoreactive implantable device with external energy transfer: Evaluation in a porcine model.

BACKGROUND: Pulmonary vein isolation (PVI) is a well-established method for the treatment of symptomatic paroxysmal atrial fibrillation, but is only partly successful with a high rate of electrical reconnection. We introduce a novel technique in which PVI is accomplished by noninvasive heating of a dedicated thermoresponse implant inserted into the pulmonary veins (PV), demonstrated in a porcine model. METHODS: A self-expanding nitinol-based implant was positioned in the common inferior PV of 11 pigs, using a fluoroscopy-guided transatrial appendage approach. Ablation was performed through contactless energy transfer from a primary extracorporal coil to a secondary heat ring (HR) embedded in the proximal part of the implant. Electrophysiological conduction was assessed prior to and postablation, and at 3 months. Histological samples were obtained acutely (n  =  4) and after 3 months (n  =  7). RESULTS: In total, 13 PV implants were successfully positioned in the inferior PVs of 11 animals. Ablation was performed without injury of adjacent structures. PVI and bidirectional block was electrophysiologically confirmed in all cases immediately at the time of implantation and 3 months later in seven chronic animals in whom testing was repeated. Marked evidence of ablation around the proximal HR was evident at 3 months postprocedure, with scar tissue formation and only mild neointimal proliferation. CONCLUSIONS: Successful PVI can be obtained by external electromagnetic heat transfer to a novel pulmonary vein implant.

Accuracy and inter-operator variability of small bowel length measurement at laparoscopy.

BACKGROUND: Measurement of bowel length is an essential surgical skill for laparoscopic and open gastrointestinal surgery in order to achieve favorable outcomes and avoid long-term complications. Variations in accuracy between the two surgical approaches may exist. However, only few studies have tried to assess these differences. Our aim was to assess reliability and inter-rater variability of small bowel length assessment during laparoscopy in an in vivo porcine model. METHODS: This is a single-institution, double-blinded, technical assessment study in a porcine in vivo model. Fourteen participants (ten senior surgeons with >1000 laparoscopic procedures and four junior surgeons) had to assess and mark lengths of small bowel in both laparoscopic and open surgical approaches. Each participant was assigned to measure and mark specific, randomized distances (range 25-197 cm) in both laparoscopic and open approaches using color-coded vessel loops. Actual participant-marked distances were compared to the assigned distances followed by Bland-Altman plots and linear regression analysis to determine accuracy and proportional error trends. Study data were further compared to available data sets from previously published studies. RESULTS: Laparoscopy measurements were significantly shorter than required (difference 33.8 ± 28.7 cm, P < 0.001, 95% CI 17.8-49.7). The measuring error was proportional to the length of the measured segment (63% of the required distances, IQR 58.9-79.0%, P = 0.02). At laparotomy, mean difference and standard deviation were lower (1.5 cm ± SD 15 cm) and not statistically significant (P = 0.7). Re-analysis of previously published data sets validated the observed errors in laparoscopic bowel measurement (P < 0.01). CONCLUSIONS: Small bowel length assessment during laparoscopy is inaccurate and associated with substantial variability. There is a need to develop a standardized laparoscopic technique for measuring small bowel length which is simple, reproducible, and easy to learn.

Further experimental evidence of the compressibility of arteries.

Further experimental evidence on the compressibility of arteries under normal physiological pressure range is provided using the experimental apparatus introduced in Yosibash et al., JMBBM 39(2014):339-354. We enlarged the experimental database by including almost twice the number of experiments, we considered a different artery - the porcine common carotid that allowed longer and larger diameters. In the physiological pressure range of 50-200mmHg, a relative volume change of 5% was obtained, lower compared to the sapheneous and femoral arteries (2-6%). Most of the arteries had a relative volume change of 1.5%. The relative volume change is found to be almost linearly proportional to the pressure, and inversely proportional to the dimensions of the experimented arteries (especially the artery length). The smaller the artery tested, the larger the relative volume change (such a phenomenon was also realized in Yosibash et al., JMBBM 39(2014):339-354.). We realized in recent past publications a flaw in the experimental protocol that results in an overestimation of the relative volume change (thus underestimating the bulk modulus). It is due to the consideration of experimental observations close to the zero pressure. Nontheless, in view of the experimental evidence, the pre-assumption of incompressibility in many phenomenological constitutive models of artery walls should be re-evaluated.

A novel secure transfixing blood vessel occluder: comparison with the hemoclip in the porcine model.

BACKGROUND: Secure vessel occlusion is critical to the success of all surgical and interventional procedures. The purpose of this study was to compare in vivo the use of the Amsel Vessel Occluder (AVO), a novel occlusion clip device for secure blood vessel closure, with one of the many commercially available hemoclips, the Ligaclip, in the porcine model. METHODS: Vessel closure of arteries and veins was performed on 10 swine to compare the ease of use, safety, and efficacy of the AVO with the Ligaclip as well as the tissue response at 7 and 30 d. After heparinization, the targeted vessels (carotid/femoral/brachial arteries and jugular/femoral/brachial veins) were occluded with two clips, either two AVO's or two Ligaclip's, and the vessels transected between the two clips. Any bleeding was recorded. At sacrifice, gross and histopathologic findings were examined for evidence of bleeding or injury to adjacent structures. The tissue response and healing were evaluated by a prospective randomized histopathologic study for the effects of any biological incompatibilities. At time of sacrifice, occluded vessel segments were subjected to nonphysiological pressures ("holding" pressures) to compare efficacy of occlusion in fresh, nonoccluded vessels, and the ability to dislodge the clips once applied. RESULTS: Twenty veins and 20 arteries between 2-mm and 7-mm outer diameter were occluded in 10 pigs. Each vessel was occluded with either AVO or Ligaclip. Our study confirmed easy and safe AVO application with no dislodgment of any AVO clips once deployed. The AVO showed no intraoperative or postoperative bleeding (AVO = 0/40), while one Ligaclip dislodged resulting in a fatal hemorrhage 16 h after surgery (Ligaclip = 1/40), and on two occasions where, with obvious slippage of the Ligaclip, immediately after deployment, additional clips were placed. The holding pressures for the two clips were similar but unlike the AVO, the Ligaclip was easily dislodged. Histopathologic examination showed no difference in the tissue response and healing of the two clips. CONCLUSIONS: The AVO is simple to deploy and securely maintains occlusion by transfixing the targeted vessel, unlike the widely used, nontransfixing Ligaclip, that has a tendency to dislodge. As such, the Amsel secure vessel occluder opens up numerous treatment opportunities in both the venous and arterial systems to minimize open, laparoscopic, robotic surgical and interventional procedures, and reduce patient morbidity and its associated health care costs.

Unlimited-Length Proctocolectomy Utilizing Sequential Intussusception and Pull-Through: Novel Clean Endolumenal NOTE-Assisted Technique With Transanal Natural Orifice Specimen Extraction Without Rectal Stump Opening in a Porcine Model.

Transanal, hybrid natural orifice translumenal endoscopic surgery (NOTES) and NOTES-assisted natural orifice specimen extraction techniques hold promise as leaders in the field of natural orifice surgery. We report the feasibility of a novel NOTES assisted technique for unlimited length, clean, endolumenal proctocolectomy in a porcine model. This technique is a modification of a transanal intussusception and pull-through procedure recently published by our group. Rectal mobilization was achieved laparoscopically; this was followed by a transanal recto-rectal intussusception and pull-through (IPT). IPT was established in a stepwise fashion. First, the proximal margin of resection was attached laparoscopically to the shaft of the anvil of an end-to-end circular stapler with a ligature around the rectum. Second, this complex was pulled transanally to produce IPT. To achieve an unlimited-length proctocolectomy, the IPT step was repeated several times prior to bowel resection. This was facilitated by removing the ligature applied in the first step of this procedure. Once sequential IPT established the desired length of bowel to be resected, a second ligature was placed around the rectum approximating the proximal and distal resection margins. The specimen was resected and extracted by making a full-thickness incision through the 2 bowel walls. The anastomosis was achieved by deploying the stapler. The technique was found to be feasible. Peritoneal samples, collected after transanal specimen extraction, did not demonstrate bacterial growth. The minimally invasive nature of this evolving technique as well as its aseptic bowel manipulation has the potential to limit the complications associated with abdominal wall incision and surgical site infection.

Biocompatibility and Systemic Safety of a Novel Implantable Annuloplasty Ring for the Treatment of Mitral Regurgitation in a Minipig Model.

Prosthetic annuloplasty rings are a common treatment modality for mitral regurgitation, and recently, percutaneous implantation techniques have gained popularity due to their favorable safety profile. Although in common use, biocompatibility of annuloplasty rings has been reported only sparsely in the literature, and none of these reports used the percutaneous technique of implantation. We report on the biocompatibility and the systemic safety of a novel transcatheter mitral valve annuloplasty ring (AMEND™) in 6 minipigs. This device is composed of a nitinol tube surrounded by a braided polyethylene terephthalate fabric tube. The device produced no adverse inflammatory response, showing gradual integration between the metal ring and the fabric by normal host fibrocellular response, leading to complete neoendocardium coverage. There was no evidence for adverse reactions, rejection, or intolerance in the valvular structure. In 2 animals, hemopericardium resulted from the implantation procedure, leading to right-sided cardiac insufficiency with pulmonary edema and liver congestion. The findings reported herein can serve as a case study for the expected healing pathology reactions after implantation of transcatheter mitral valve annuloplasty rings.

Feasibility of an Intraluminal Bypass Device in Low Colorectal Anastomosis: Preliminary Results in a Porcine Model.

BACKGROUND: The Cologuard CG-100 is a novel intraluminal bypass device designed to reduce the clinical outcomes associated with low colorectal anastomotic leak. The device is inserted transanally, anchored to the colon above the anastomosis, and deployed intraluminally to cover the anastomosis from within. The purpose of this study was to evaluate the safety and performance of the device in a porcine model. METHOD: Twelve pigs underwent low colorectal anastomosis with insertion of the Cologuard CG-100 device. Contrast material injection, abdominal X-ray, and histologic studies were used to evaluate sealing quality, device positioning, and tissue damage, respectively. The surgeons completed a usability and satisfaction questionnaire after completion of the procedure. RESULTS: Absolute sealing was observed in all 4 animals euthanized immediately after surgery. In the other 8 animals, the device was kept in situ for 10 days and then extracted. X-ray films with injection of contrast material through a designated injection tube before device removal showed that the sheath and ring were correctly placed. No leak was demonstrated. There were no device-related adverse events, and no critical histological abnormalities were noted in the bowel area that was compressed by the device. The device was found to be easy to insert, position, and extract. CONCLUSION: The Cologuard CG-100 device efficiently reduced contact between fecal content and low colorectal anastomosis in a porcine model and is easily deployed and extracted. It holds promise for possible clinical use pending further studies.

Static laser speckle contrast analysis for noninvasive burn diagnosis using a camera-phone imager.

Laser speckle contrast analysis (LASCA) is an established optical technique for accurate widefield visualization of relative blood perfusion when no or minimal scattering from static tissue elements is present, as demonstrated, for example, in LASCA imaging of the exposed cortex. However, when LASCA is applied to diagnosis of burn wounds, light is backscattered from both moving blood and static burn scatterers, and thus the spatial speckle contrast includes both perfusion and nonperfusion components and cannot be straightforwardly associated to blood flow. We extract from speckle contrast images of burn wounds the nonperfusion (static) component and discover that it conveys useful information on the ratio of static-to-dynamic scattering composition of the wound, enabling identification of burns of different depth in a porcine model in vivo within the first 48 h postburn. Our findings suggest that relative changes in the static-to-dynamic scattering composition of burns can dominate relative changes in blood flow for burns of different severity. Unlike conventional LASCA systems that employ scientific or industrial-grade cameras, our LASCA system is realized here using a camera phone, showing the potential to enable LASCA-based burn diagnosis with a simple imager.

3-Methyl-methcathinone: Pharmacokinetic profile evaluation in pigs in relation to pharmacodynamics.

3-Methyl-methcathinone (3-MMC) is a novel, synthetic cathinone analog, recently linked to poisoning events among recreational users. The lack of pharmacological data on 3-MMC, prompted us to explore its pharmacokinetic profile as well as its effect on feeding behavior, weight gain, and serum biochemistry. 3-MMC was administered to male pigs (n=3, three months old) as a single intravenous dose (0.3 mg/kg), followed by a multiple oral dose administration (3 mg/kg) for five days and plasma and tissue concentrations determined. Concomitantly a control group consisting of two healthy male pigs received saline solution instead of 3-MMC according to the same administration schedule. 3-MMC effects on complete blood count, biochemistry, feed intake, and body weight were examined. The pigs were sacrificed and submitted to a pathological and histopathological examination. 3-MMC displayed rapid absorption with a peak concentration achieved within 5-10 min after oral ingestion and a plasma half-life of 0.8 h. The bioavailability was about 7%. 3-MMC tissue levels were below detectable levels 24 h after the last oral dosage. No treatment-related clinical signs were observed and no histopathological findings were detected. 3-MMC caused significant change in daily feed intake and weight gain over time. The animals treated with 3-MMC displayed a lower rate of increase in mean body weight. Caution needs to be practiced in terms of extrapolating the present data to human safety, due to the low sample size, low dosage, and the relatively short study duration as well as the lack of data on abuse potential of 3-MMC.

Novel Totally Laparoscopic Endolumenal Rectal Resection With Transanal Natural Orifice Specimen Extraction (NOSE) Without Rectal Stump Opening: A Modification of Our Recently Published Clean Surgical Technique in a Porcine Model.

Our group has recently described a novel technique for clean endolumenal bowel resection, in which abdominal and transanal approaches were used. In the current study, 2 modifications of this procedure were tested for feasibility in a porcine model. A laparoscopic approach to the peritoneal cavity was employed in rectal mobilization; this was followed by a transanal rectorectal intussusception and pull-through (IPT). IPT was established in a stepwise fashion. First, the proximal margin of resection was attached to the shaft of the anvil of an end-to-end circular stapler with a ligature around the rectum. Second, this complex was pulled transanally to produce IPT. Once IPT was established, a second ligature was placed around the rectum approximating the proximal and distal resection margins. This was followed by a purse string suture through 2 bowel walls, encircling the shaft of the anvil just proximal to the ligatures. The specimen was resected and extracted by making a full-thickness incision through the 2 bowel walls distal to the previously placed purse string suture and ligatures. The anastomosis was achieved by applying the stapler. The technique was found to be feasible. Peritoneal samples, collected after transanal specimen extraction, did not demonstrate bacterial growth. Although, this is a novel and evolving procedure, its minimally invasive nature, as well as aseptic bowel manipulation during endolumenal rectal resection, has the potential to limit the complications associated with abdominal wall incision and surgical site infection.

The efficacy of an immunoisolating membrane system for islet xenotransplantation in minipigs.

Developing a device that protects xenogeneic islets to allow treatment and potentially cure of diabetes in large mammals has been a major challenge in the past decade. Using xenogeneic islets for transplantation is required in light of donor shortage and the large number of diabetic patients that qualify for islet transplantation. Until now, however, host immunoreactivity against the xenogeneic graft has been a major drawback for the use of porcine islets. Our study demonstrates the applicability of a novel immunoprotective membrane that allows successful xenotransplantation of rat islets in diabetic minipigs without immunosuppressive therapy. Rat pancreatic islets were encapsulated in highly purified alginate and integrated into a plastic macrochamber covered by a poly-membrane for subcutaneous transplantation. Diabetic Sinclair pigs were transplanted and followed for up to 90 days. We demonstrated a persistent graft function and restoration of normoglycemia without the need for immunosuppressive therapy. This concept could potentially offer an attractive strategy for a more widespread islet replacement therapy that would restore endogenous insulin secretion in diabetic patients without the need for immunosuppressive drugs and may even open up an avenue for safe utilization of xenogeneic islet donors.

Healing of ileocolic nitinol compression anastomosis: a novel porcine model of subtotal colectomy.

BACKGROUND: There are limited large animal models for the research of novel anastomotic technologies. Subtotal colectomy requires the anastomosis of relatively remote segments of the alimentary tract that are different anatomically, histologically, and pose significant physiological challenge. The quest for a foreign material-free anastomotic line reintroduced nitinol compression anastomosis into clinical use in the last decade. OBJECTIVE: To evaluate the safety, histological, and physiological parameters of side-to-side ileocolic nitinol compression anastomosis in a newly developed large animal model, mimicking the human subtotal colectomy. INTERVENTION: Resection of the entire spiral colon with an ileocolic side-to-side compression anastomosis in 12 animals, compared to resection of a short ileal segment in 6 animals. All anastomoses were constructed by using a novel nitinol-based compression device. The animals were followed up to 30 days postoperatively and were reoperated and sacrificed. RESULTS: All 12 animals underwent successful subtotal colectomy with side-to-side nitinol compression anastomosis. No signs of abdominal infection were found. The increase in the colectomized animals' bodyweight over the postoperative course was significantly lower and the animals presented with longer periods of diarrhea. The histopathology revealed minimal inflammation and foreign body reaction with good alignment of the bowel wall layers in both groups. The anastomotic line width was shown to be reduced during the healing course of the compression anastomoses. CONCLUSIONS: Side-to-side nitinol compression anastomosis is safe and demonstrates favorable functional and histopathological features. The porcine model of subtotal colectomy can be used for further research of novel anastomotic technologies.

Endolumenal rectal resection and transanal natural orifice specimen extraction (NOSE) without rectal stump opening: a novel, clean surgical technique in a porcine model.

Minimally invasive surgery has been continuously evolving over the past 20 years. The use of natural orifice specimen extraction (NOSE) is one of the most recent contributions to minimally invasive methods. The anus has been widely used in NOSE procedures. However, an open rectal stump carries the highest risk of contamination compared with other translumenal approaches to the peritoneal cavity. In this study, the feasibility of a novel NOSE method was tested in a porcine model. This technique combined abdominal and transanal approaches. The abdominal approach was used in rectal mobilization; this was followed by a transanal recto-rectal intussusception and pull-through (IPT). IPT was established in a stepwise fashion. First, the proximal margin of resection was attached to the shaft of the anvil of an end-to-end circular stapler with a ligature around the rectum. Second, this complex was pulled transanally to produce IPT. Once IPT was established, a second ligature was placed around the rectum, approximating the proximal and distal resection margins. The specimen was resected and extracted by making a full-thickness incision through 2 bowel walls distal to the previously placed ligatures. Anastomosis was achieved by applying the stapler. The technique was found to be feasible. A substantial length of bowel was resected in all experiments. Peritoneal samples, collected after transanal specimen extraction, did not demonstrate bacterial growth. Although more investigation is warranted, this procedure has the potential to limit surgical site infections by using aseptic bowel manipulation during colorectal resection and transanal specimen extraction.

Intracoronary injection of in situ forming alginate hydrogel reverses left ventricular remodeling after myocardial infarction in Swine.

OBJECTIVES: This study sought to determine whether alginate biomaterial can be delivered effectively into the infarcted myocardium by intracoronary injection to prevent left ventricular (LV) remodeling early after myocardial infarction (MI). BACKGROUND: Although injectable biomaterials can improve infarct healing and repair, the feasibility and effectiveness of intracoronary injection have not been studied. METHODS: We prepared a calcium cross-linked alginate solution that undergoes liquid to gel phase transition after deposition in infarcted myocardium. Anterior MI was induced in swine by transient balloon occlusion of left anterior descending coronary artery. At 4 days after MI, either alginate solution (2 or 4 ml) or saline was injected selectively into the infarct-related coronary artery. An additional group (n = 19) was treated with incremental volumes of biomaterial (1, 2, and 4 ml) or 2 ml saline and underwent serial echocardiography studies. RESULTS: Examination of hearts harvested after injection showed that the alginate crossed the infarcted leaky vessels and was deposited as hydrogel in the infarcted tissue. At 60 days, control swine experienced an increase in left ventricular (LV) diastolic area by 44%, LV systolic area by 45%, and LV mass by 35%. In contrast, intracoronary injection of alginate (2 and 4 ml) prevented and even reversed LV enlargement (p < 0.01). Post-mortem analysis showed that the biomaterial (2 ml) increased scar thickness by 53% compared with control (2.9 +/- 0.1 mm vs. 1.9 +/- 0.3 mm; p < 0.01) and was replaced by myofibroblasts and collagen. CONCLUSIONS: Intracoronary injection of alginate biomaterial is feasible, safe, and effective. Our findings suggest a new percutaneous intervention to improve infarct repair and prevent adverse remodeling after reperfused MI.