A porcine model of thoracic aortic aneurysms created with a retrievable drug infusion stent graft mirrors human aneurysm pathophysiology.

Objective: Aneurysm pathophysiology remains poorly understood, in part from the disparity of murine models with human physiology and the requirement for invasive aortic exposure to apply agents used to create aneurysm models. A retrievable drug infusion stent graft (RDIS) was developed to isolate the aortic wall intraluminally for drug exposure. We hypothesized that an RDIS could deliver aneurysm-promoting enzymes to create a porcine model of thoracic aneurysms without major surgical exposure.

A self calibrating, magnetic sensor approach accurately positions an aortic damage control stent in a porcine model.

Objectives: Non-compressible torso hemorrhage remains a high mortality injury, with difficulty mobilizing resources before exsanguination. Previous studies reported on a retrievable stent graft for damage control and morphometric algorithms for rapid placement, yet fluoroscopy is impractical for the austere environment. We hypothesized that magnetic sensors could be used to position stents relative to an external magnet placed on an anatomic landmark, whereas an electromagnet would allow self-calibration to account for environmental noise.

A dumbbell rescue stent graft facilitates clamp-free repair of aortic injury in a porcine model.

Objective: Noncompressible torso hemorrhage is a high-mortality injury. We previously reported improved outcomes with a retrievable rescue stent graft to temporize aortic hemorrhage in a porcine model while maintaining distal perfusion. A limitation was that the original cylindrical stent graft design prohibited simultaneous vascular repair, given the concern for suture ensnarement of the temporary stent.

A prebifurcated axillobifemoral polytetrafluoroethylene graft simplifies carotid to carotid to subclavian bypass.

The use of thoracic endovascular aortic repair for thoracic aortic disease will necessitate cervical debranching in cases involving the proximal arch. We have presented the case of a 57-year-old athletic woman who had developed a type A dissection that extended to the bilateral iliac arteries. After hemiarch repair, she underwent staged cervical debranching with carotid-carotid-subclavian bypass using a prebifurcated axillobifemoral graft and subsequent thoracic endovascular aortic repair.

The anchor point algorithm: A morphometric analysis of anatomic landmarks to guide placement of temporary aortic Rescue stent grafts for noncompressible torso hemorrhage.

Background: Noncompressible hemorrhage remains a high-mortality injury, which requires rapid damage control within minutes to avoid exsanguination. Retrievable stent grafts offer perfusion preserving hemorrhage damage control, and yet algorithms for device selection and positioning are lacking for an anatomically diverse human population. We hypothesized that easily acquired external measurements could be used to rapidly triage patients to receive one of several presized stents and that these metrics may further predict a single target on the aorta by which to optimize both mesenteric perfusion and aortic hemorrhage control.

Understanding the Mechanism of Drug Transfer and Retention of Drug-Coated Balloons.

Objective: The purpose of this study was to determine the impact of varying inflation parameters on paclitaxel delivery and retention using a commercially available DCB.

Background: Drug-coated balloons (DCB) have become the standard treatment for peripheral artery disease. Clinical data suggest that varying DCB delivery parameters directly impact patient outcome.

A retrievable, dual-chamber stent protects against warm ischemia of donor organs in a model of donation after circulatory death.

Background: Ischemic injury during the agonal period of donation after circulatory death donors remains a significant barrier to increasing abdominal transplants. A major obstacle has been the inability to improve visceral perfusion, while at the same time respecting the ethics of the organ donor. A retrievable dual-chamber stentgraft could potentially isolate the organ perfusion from systemic hypotension and hypoxia, without increasing cardiac work or committing the donor.

Assessment of mechanical and biocompatible performance of ultra-large nitinol endovascular devices fabricated via a low-energy laser joining process.

Nitinol is an excellent candidate material for developing various self-expanding endovascular devices due to its unique properties such as superelasticity, biocompatibility and shape memory effect. A low-energy laser joining technique suggests a high potential to create various large diameter Nitinol endovascular devices that contain complex geometries. The primary purpose of the study is to investigate the effects of laser joining process parameters with regard to the mechanical and biocompatible performance of Nitinol stents.

A three-tier Rescue stent improves outcomes over balloon occlusion in a porcine model of noncompressible hemorrhage.

Background: Noncompressible hemorrhage remains a high-mortality injury, and aortic balloon occlusion poses limitations in terms of distal ischemic injury. Our hypothesis was that a retrievable Rescue stent would confer improved outcome over aortic balloon occlusion.

Methods: A three-tier, retrievable stent graft was laser welded from nitinol and polytetrafluoroethylene to provide rapid thoracic and abdominal coverage with an interval bare metal segment to preserve visceral flow.

Comprehensive assessment of mechanical behavior of an extremely long stent graft to control hemorrhage in torso.

Traumatic vascular injuries, resulting from either civilian accidents or wounded soldiers, require new endovascular devices (i.e., stent graft) to rapidly control the excessive internal hemorrhage in torso region.

Damage control of caval injuries in a porcine model using a retrievable Rescue stent.

Objective: Early hemorrhage control before the operating room is essential to reduce the significant mortality associated with traumatic injuries of the vena cava. Conventional approaches present logistical challenges on the battlefield or in the trauma bay. A retrievable stent graft would allow rapid hemorrhage control in the preoperative setting when endovascular expertise is not immediately available and without committing a patient to the limitations of current permanent stents.

Advances in Materials for Recent Low-Profile Implantable Bioelectronics.

The rapid development of micro/nanofabrication technologies to engineer a variety of materials has enabled new types of bioelectronics for health monitoring and disease diagnostics. In this review, we summarize widely used electronic materials in recent low-profile implantable systems, including traditional metals and semiconductors, soft polymers, biodegradable metals, and organic materials. Silicon-based compounds have represented the traditional materials in medical devices, due to the fully established fabrication processes.

A retrievable rescue stent graft and radiofrequency positioning for rapid control of noncompressible hemorrhage.

Background: Noncompressible hemorrhage of the torso remains a challenging surgical dilemma. Stent graft repair requires endovascular expertise, imaging, and inventory that are not available within the critical window of massive hemorrhage. We developed a retrievable stent graft for rapid hemorrhage.

An in vivo pilot study of a microporous thin film nitinol-covered stent to assess the effect of porosity and pore geometry on device interaction with the vessel wall.

Sputter-deposited thin film nitinol constructs with various micropatterns were fabricated to evaluate their effect on the vessel wall in vivo when used as a covering for commercially available stents. Thin film nitinol constructs were used to cover stents and deployed in non-diseased swine arteries. Swine were sacrificed after approximately four weeks and the thin film nitinol-covered stents were removed for histopathologic evaluation.

A novel compartmentalised stent graft to isolate the perfusion of the abdominal organs.

Donation after cardiac death has been adopted to address the critical shortage of donor organs for transplant. Recovery of these organs is hindered by low blood flow that leads to permanent organ injury. We propose a novel approach to isolate the perfusion of the abdominal organs from the systemic malperfusion of the dying donor.

A depleting antibody toward sca-1 mitigates a surge of CD34(+)/c-kit(+) progenitors and reduces vascular restenosis in a murine vascular injury model.

Objective: Vascular restenosis remains a major obstacle to long-term success after vascular intervention. Circulating progenitor cells have been implicated in restenosis, and yet it has remained unclear if these cells, particularly nonendothelial progenitors, have an active role in this pathologic process. We hypothesized that circulating CD34(+)/c-kit(+) progenitors would increase after vascular injury, mirrored by changes in the injury signal, stromal cell-derived factor 1α (sdf1α).

Dual chamber stent prevents organ malperfusion in a model of donation after cardiac death.

Background: The paradigm for donation after cardiac death subjects donor organs to ischemic injury. A dual-chamber organ perfusion stent would maintain organ perfusion without affecting natural cardiac death. A center lumen allows uninterrupted cardiac blood flow, while an external chamber delivers oxygenated blood to the visceral vessels.

CD34 affinity pheresis attenuates a surge among circulating progenitor cells following vascular injury.

Background: Intimal hyperplasia (restenosis) is an exaggerated healing response leading to failure of half of vascular interventions. Increasing evidence suggests that circulating progenitor cells contribute to intimal pathology, and clinical studies have demonstrated a correlation between progenitor cells and the incidence of restenosis after cardiovascular interventions. The aims of this study were to characterize the temporal response of CD34+ progenitors following vascular injury in an ovine model and to evaluate an affinity pheresis approach to attenuate this response.

Bioengineered vascular access maintains structural integrity in response to arteriovenous flow and repeated needle puncture.

Objective: Tissue-engineered blood vessels (TEBV) have been proposed as an alternative to prosthetic grafts for dialysis access. However, arteriovenous (AV) grafts must withstand extreme flow rates and frequent needle trauma. In a proof-of-concept study, we sought to determine whether scaffold-based TEBV could withstand the hemodynamic and mechanical challenges of chronic dialysis access.

Vascular smooth muscle enhances functionality of tissue-engineered blood vessels in vivo.

Objectives: There is significant room for improvement in the development of tissue-engineered blood vessels (TEBVs) for vascular reconstruction. Most commonly, TEBVs are seeded with endothelial cells (ECs) only. This provides an antithrombogenic surface but suboptimal physiologic characteristics compared with native arteries, due to lack of smooth muscle cells (SMCs) in the vessel media.

The fate of an endothelium layer after preconditioning.

Background: A strategy in minimizing thrombotic events of vascular constructs is to seed the luminal surface with autologous endothelial cells (ECs). The task of seeding ECs can be achieved via bioreactors, which induce mechanical forces (shear stress, strain, pressure) onto the ECs. Although bioreactors can achieve a confluent layer of ECs in vitro, their acute response to blood remains unclear.

Efficient recovery of endothelial progenitors for clinical translation.

Background: Circulating autologous CD133+ stem cells have been differentiated into a number of cell types that have the potential for clinical use, including endothelial cells. These cells are infrequently found in peripheral blood specimens, and this limits their use in clinical applications. To address this problem, we have developed an extracorporeal cellular affinity (ECA) column that can recover CD133 expressing progenitor cells with high efficiency.

The in vivo stability of electrospun polycaprolactone-collagen scaffolds in vascular reconstruction.

To avoid complications of prosthetic vascular grafts, engineered vascular constructs have been investigated as an alternative for vascular reconstruction. The scaffolds for vascular tissue engineering remain a cornerstone of these efforts and yet many currently available options are limited by issues of inconsistency, poor adherence of vascular cells, or inadequate biomechanical properties. In this study, we investigated whether PCL/collagen scaffolds could support cell growth and withstand physiologic conditions while maintaining patency in a rabbit aortoiliac bypass model.