Development of a clinically relevant ex vivo model of cardiac ablation for testing of ablation catheters.

INTRODUCTION: Reliable ex vivo cardiac ablation models have the potential to increase catheter testing throughput while minimizing animal usage. The goal of this work was to develop a physiologically relevant ex vivo swine model of cardiac ablation displaying minimal variability and high repeatability and identify and optimize key parameters involved in ablation outcomes. METHODS AND RESULTS: A root cause analysis was conducted to identify variables affecting ablation outcomes. Parameters associated with the tissue, bath media, and impedance were identified. Variables were defined experimentally and/or from literature sources to best mimic the clinical cardiac ablation setting. The model was validated by performing three independent replicates of ex vivo myocardial ablation and a direct comparison of lesion outcomes of the ex vivo swine myocardial and in vivo canine thigh preparation (TP) models. Replicate experiments on the ex vivo model demonstrated low variance in ablation depth (6.5 ± 0.6, 6.3 ± 0.6, 6.2 ± 0.4 mm) and width (10.4 ± 1.1, 9.7 ± 1.0, 9.9 ± 0.9 mm) and no significant differences between replicates. In a direct comparison of the two models, the ex vivo model demonstrated ablation depths similar to the canine TP model at 35 W (6.9 ± 1.0, and 7.0 ± 0.9 mm) and 50 W (8.0 ± 0.7, and 8.4 ± 0.7 mm), as well as similar power to depth ratios (15% and 19% for the ex vivo cardiac and in vivo TP models, respectively). CONCLUSION: The ex vivo model exhibited strong lesion reproducibility and power-to-depth ratios comparable to the in vivo TP model. The optimized ex vivo model minimizes animal usage with increased throughput, lesion characteristics similar to the in vivo TP model, and ability to discriminate minor variations between different catheter designs.

Device safety assessment of bronchoscopic microwave ablation of normal swine peripheral lung using robotic-assisted bronchoscopy.

INTRODUCTION: The aim of this study was to assess the safety of bronchoscopic microwave ablation (MWA) of peripheral lung parenchyma using the NEUWAVE™ FLEX Microwave Ablation System, and robotic-assisted bronchoscopy (RAB) using the MONARCH™ Platform in a swine model. METHODS: Computed tomography (CT)-guided RAB MWA was performed in the peripheral lung parenchyma of 17 Yorkshire swine (40-50 kg) and procedural adverse events (AEs) documented. The acute group (day 0, n = 5) received 4 MWAs at 100 W for 1, 3, 5, and 10 min in 4 different lung lobes. Subacute and chronic groups (days 3 and 30, n = 6 each) received one MWA (100 W, 10 min) per animal. RESULTS: The study was completed without major procedural complications. No postprocedural AEs including death, pneumothorax, bronchopleural fistula, hemothorax, or pleural effusions were observed. No gross or histological findings suggestive of thromboembolism were found in any organ. One 3-Day and one 30-Day swine exhibited coughing that required no medication (minor AEs), and one 30-Day animal required antibiotic medication (major AE) for a suspected lower respiratory tract infection that subsided after two weeks. CT-based volumetric estimates of ablation zones in the acute group increased in an ablation time-dependent (1-10 min) manner, whereas macroscopy-based estimates showed an increasing trend in ablation zone size. CONCLUSION: The NEUWAVE FLEX and MONARCH devices were safely used to perform single or multiple RAB MWAs. The preclinical procedural safety profile of RAB MWA supports clinical research of both devices to investigate efficacy in select patients with oligometastatic disease or primary NSCLC.

Is Circular Fibrin Sealing of Low Rectal Anastomosis Able to Prevent Leakage in 21-Day Follow-up? Randomized Experimental Trial in Pigs.

Purpose. Clinically apparent anastomotic leakage (AL) after low anterior rectal resection (LAR; <7 cm from anal verge) using circular double-stapled anastomosis without defunctioning stoma is up to 37.5%. However, it is unclear whether there is reduction of LAR after 21 postoperative days without defunctioning stoma but with extraluminal anastomotic application of fibrin sealant. Methods. Forty-eight-week-old pigs underwent LAR and circular double-stapled anastomosis in end-to-end technique (descendo-rectostomy). Animals were randomized into therapy and control group (cg). Therapy group (n = 20) received additional extraluminal circular anastomotic application of fibrin sealant. Objective was to assess incidence of clinically apparent and nonclinically apparent leakage through the 21st postoperative day. Remaining animals were sacrificed on the 21st day, and anastomotic region was analyzed. In case of earlier diagnosed AL, animals were sacrificed. Results. In cg, we observed clinically and nonclinically AL in 20% (n = 4). No animal was identified with a nonclinical-apparent leakage in this group, and all 4 animals with leakages presented clinical signs. In the therapy group, no animal (0/20) developed clinically apparent leakage signs. There were no leakages in this group, but 3 animals had ulcerative lesions without leak and without clinical signs. These lesions were observed intraluminally at crossing of staple lines after 21 days. In one of these animals, incomplete leakage was observed, blocked by fibrin sealant. Conclusion. In circular stapled colorectal anastomosis, circular fibrin glue sealant successfully protected anastomotic intraluminal wall defects at crossing of staple lines, reducing leakage rate from 20% to 0% (cg vs therapy group) after 21 postoperative days.

Comparing the Water-Tight Closure of Barbed and Conventional Suture Under Static and Dynamic Conditions in an Ex-Vivo Human Knee Arthrotomy Model.

BACKGROUND: Barbed suture has become popular for closure of the arthrotomy and overlying tissues in total knee arthroplasty. STRATAFIX Symmetric PDS Knotless Tissue Control Device, a unique and novel barbed suture, with barbs formed integral to the suture core provides greater suture strength than the more common cut barbed suture designs. It is the only barbed suture commercially available with an indication in high tension areas, such as fascia. The purpose of this study was to evaluate the use of this novel barbed suture in the formation of a water-tight arthrotomy closure, using a continuous suture pattern, compared to conventional Coated VICRYL (polyglactin 910) Suture, using an interrupted suture pattern, in a cadaveric knee arthrotomy. METHODS: Twenty fresh-frozen cadaver knees underwent randomization to provide donor-paired matching of the knee arthrotomy closures using barbed suture in a continuous pattern or conventional suture in an interrupted pattern. Each specimen underwent 5 phases of testing that included 1) predynamic static leak testing; 2) dynamic motion leak testing; 3) postdynamic static leak testing; 4) suture release static leak testing; and 5) postsuture release dynamic motion leak testing, to assess the fluid leak rate. RESULTS: Under the initial static conditions, watertightness was similar for the 2 types of sutures. However, in all subsequent phases of testing, continuous barbed suture created a better watertight closure than interrupted conventional suture. CONCLUSIONS: In this study, it was observed that closure of a knee arthrotomy using the novel barbed suture provided improved watertightness compared to conventional interrupted closure under dynamic conditions and suture release.

S2 connector versus suture: distal coronary anastomosis remodeling, patency, and function in the pig.

BACKGROUND: Anastomotic connectors could be the key to less invasive bypass surgery, including endoscopic procedures, but equivalence to conventional suturing needs to be established. A novel distal coronary connector was tested pre-clinically for safety and efficacy in comparison to conventional suturing. METHODS AND RESULTS: Left internal thoracic to left anterior descending coronary artery bypasses were constructed off-pump in 35 pigs (73+/-8 kg). An intraluminal metal connector (S2AS) was used in 21 and conventional suturing in 14 animals. S2AS anastomosis construction was easier achieved in one-fourth of the conventional construction time (3.7+/-0.7 versus 16.5+/-2.6 minutes; P<0.001). Acute patency tended to be better (P=0.15). All anastomoses were evaluated intraoperatively, and subgroups at 90 and at 180 days. Patency was 100%. An effective remodeling response was observed in all groups, resulting in unobstructed anastomoses with excellent hemodynamic performance (fractional flow reserve > or = 0.93 at 180 days). At 6 months, the noncompliant connector was covered with stabilized neointima that was thinner than found on the suture line (0.10+/-0.04 versus 0.31+/-0.13 mm; P=0.01). The connector induced less lumen loss (-0.6+/-6.5 versus 21.6+/-19%; P=0.03). The initial side-to-side configuration had remodeled to an end-to-side shape as intended. CONCLUSIONS: In the porcine model, the connector rapidly and consistently produced high-quality anastomoses that fully met current standards on patency and function. Unconventional aspects like a noncompliant intraluminal ring and a side-to-side to end-to-side converted configuration did not interfere with favorable anastomosis remodeling. These findings shed a new light on the anatomical prerequisites for anastomosis patency.

Hemostatic efficacy of EVARREST™, Fibrin Sealant Patch vs. TachoSil® in a heparinized swine spleen incision model.

BACKGROUND: First-generation single-component hemostats such as oxidized regenerated cellulose (ORC), fibrin, collagen, and gelatin have evolved into second and third generations of combination hemostats. OBJECTIVE: This study compares two FDA approved products, EVARREST™, Fibrin Sealant Patch, a hemostat comprised of a matrix of nonwoven polyglactin 910 embedded in ORC coated with human fibrinogen and thrombin to TachoSil® medicated sponge, an equine collagen pad coated with human fibrinogen and thrombin. MATERIALS AND METHODS: Swine were anticoagulated with heparin to 3X their baseline activated clotting time and a 15 mm long × 3 mm deep incision was made to create a consistent moderate bleeding pattern. Test material was then applied to the wound site and compressed manually for 3 min with just enough pressure to prevent continued bleeding. Hemostatic effectiveness was evaluated at 3 min and 10 min. RESULTS: At 3 min, the hemostasis success rate was 86% in the EVARREST™ group and 0% in the TachoSil® group, p < .0001. The overall success rate at 10 min was 100% with EVARREST™ and 4% with TachoSil®, p < .0001. Adhesive failure, in which the test material did not stick to the tissue, occurred in 96% of TachoSil® sites. In contrast, 100% of the EVARREST™ applications adhered to the test site. CONCLUSIONS: EVARREST™, Fibrin Sealant Patch demonstrated greater wound adhesion and more effective hemostasis than TachoSil®. Adhesive failure was the primary failure mode for TachoSil® in this model.