Michael J. Byrom

A multilayered synthetic human elastin/polycaprolactone hybrid vascular graft with tailored mechanical properties.

Small-diameter synthetic vascular graft materials fail to match the patency of human tissue conduits used in vascular bypass surgery. The foreign surface retards endothelialization and is highly thrombogenic, while the mismatch in mechanical properties induces intimal hyperplasia. Using recombinant human tropoelastin, we have developed a synthetic vascular conduit for small-diameter applications. We show that tropoelastin enhances endothelial cell attachment (threefold vs. control) and proliferation by 54.7 ± 1.1% (3 days vs. control). Tropoelastin, when presented as a monomer and when cross-linked into synthetic elastin for biomaterials applications, had low thrombogenicity. Activation of the intrinsic pathway of coagulation, measured by plasma clotting time, was reduced for tropoelastin (60.4 ± 8.2% vs. control). Platelet attachment was also reduced compared to collagen. Reductions in platelet interactions were mirrored on cross-linked synthetic elastin scaffolds. Tropoelastin was subsequently incorporated into a synthetic elastin/polycaprolactone conduit with mechanical properties optimized to mimic the human internal mammary artery, including permeability, compliance, elastic modulus and burst pressure. Further, this multilayered conduit presented a synthetic elastin internal lamina to circulating blood and demonstrated suturability and mechanical durability in a small scale rabbit carotid interposition model.

Covalent immobilisation of tropoelastin on a plasma deposited interface for enhancement of endothelialisation on metal surfaces

Currently available endovascular metallic implants such as stents exhibit suboptimal biocompatibility in that they re-endothelialise poorly leaving them susceptible to thrombosis. To improve the interaction of these implants with endothelial cells we developed a surface coating technology, enabling the covalent attachment of biomolecules to previously inert metal surfaces. Using horseradish peroxidase as a probe, we demonstrate that the polymerised surface can retain the presentation and activity of an immobilised protein. We further demonstrated the attachment of tropoelastin, an extracellular matrix protein critical to the correct arrangement and function of vasculature. Not only it is structurally important, but it plays a major role in supporting endothelial cell growth, while modulating smooth muscle cell infiltration. Tropoelastin was shown to bind to the surface in a covalent monolayer, supplemented with additional physisorbed multilayers on extended incubation. The physisorbed tropoelastin layers can be washed away in buffer or SDS while the first layer of tropoelastin remains tightly bound. The plasma coated stainless steel surface with immobilised tropoelastin was subsequently found to have improved biocompatibility by promoting endothelial cell attachment and proliferation relative to uncoated stainless steel controls. Tropoelastin coatings applied to otherwise inert substrates using this technology could thus have broad applications to a range of non-polymeric vascular devices.

Animal models for the assessment of novel vascular conduits

The development of an ideal small-diameter conduit for use in vascular bypass surgery has yet to be achieved. The ongoing innovation in biomaterial design generates novel conduits that require preclinical assessment in vivo, and a number of animal models have been used for this purpose. This article examines the rationale behind animal models used in the assessment of small-diameter vascular conduits encompassing the commonly used species: baboons, sheep, pigs, dogs, rabbits, and rodents. Studies on the comparative hematology for these species relative to humans are summarized, and the hydrodynamic values for common implant locations are also compared. The large- and small-animal models are then explored, highlighting the characteristics of each that determine their relative utility in the assessment of vascular conduits. Where possible, the performance of expanded polytetrafluoroethylene is given in each animal and in each location to allow direct comparisons between species. New challenges in animal modeling are outlined for the assessment of tissue-engineered graft designs. Finally, recommendations are given for the selection of animal models for the assessment of future vascular conduits.

Long-term prognosis and cost-effectiveness of left ventricular assist device as bridge to transplantation: a systematic review

BACKGROUND This systematic review aimed to evaluate the clinical outcomes and cost-effectiveness of left ventricular assist devices (LVADs) used as bridge to transplantation (BTT), compared to orthotopic heart transplantation (OHT) without a bridge. METHOD Systematic searches were performed in electronic databases with available data extracted from text and digitized figures. Meta-analysis of short and long-term term post-transplantation outcomes was performed with summation of cost-effectiveness analyses. RESULTS Twenty studies reported clinical outcomes of 4575 patients (1083 LVAD BTT and 3492 OHT). Five studies reported cost-effectiveness data on 837 patients (339 VAD BTT and 498 OHT). There was no difference in long-term post-transplantation survival (HR 1.24, 95% CI 1.00-1.54), acute rejection (HR 1.10, 95% CI 0.93-1.30), or chronic rejection and cardiac allograft vasculopathy (HR 0.99, 95% CI 0.73-1.36). No differences were found in 30-day post-operative mortality (OR 0.91, 95% CI 0.42-2.00), stroke (OR 1.64, 95% CI 0.43-6.27), renal failure (OR 1.43, 95% CI 0.58-3.54), bleeding (OR 1.56, 95% CI 0.78-3.13), or infection (OR 2.44, 95% CI 0.81-7.38). Three of the five studies demonstrated incremental cost-effectiveness ratios below the acceptable maximum threshold. The total cost of VAD BTT ranged from

Neurologic injury and protection in adult cardiac and aortic surgery

316,078 to

Acute limb ischemia eight months after a Bentall procedure.

1,025,500, and OHT ranged from

Pig model gets to the dogma

179,051 to

How many sutures should a sutureless valve need

802,200. CONCLUSION LVADs used as BTT did not significantly alter post-transplantation long-term survival, rejection, and post-operative morbidity. LVAD BTT may be cost-effective, particularly in medium and high-risk patients with expected prolonged waiting times, renal dysfunction, and young patients.

Acetylene plasma polymerized surfaces for covalent immobilization of dense bioactive protein monolayers

EUROLOGIC INJURY can be defined as any temporary or permanent injury to the central and peripheral nervous system, including the brain, spinal cord, and peripheral nerves. This is a major perioperative complication of cardiac and aortic surgery, which can manifest as short-term coma or a state of confusion and long-term decline in cognitive function, behavioral changes, or physical dysfunction. Stroke occurs in approximately 2% to 3% of adult cardiac surgery patients. The rate of postoperative cognitive decline is less clear, due to heterogenous testing methods, but is reported in 50% to 70% of patients at 1 week, 30% to 50% at 6 weeks, and 20% to 40% at 1 year. 1,2 This review evaluates the current rationale and evidence for proposed surgical and nonsurgical techniques for the reduction of neurologic injury. A variety of mechanisms can result in perioperative neurologic injury during cardiac and aortic surgery (Table 1), and many patients have a combination of these mechanisms. This review discusses these etiologic factors in relation to the techniques proposed to reduce them. Accurate assessment techniques to determine the etiology of neurologic injury, adequacy of cerebral perfusion, and quantification of the extent of injury are essential to assess the efficacy of potential neuroprotective measures. These techniques include intraoperative near-infrared spectroscopy and transcranial Doppler; neurologic, psychological, and cognitive examination; imaging of the nervous system; and biomarkers in cerebrospinal fluid and serum. Discussion of these methods are outside the scope of this review; however, it is important to appreciate that all methods have limitations in sensitivity and/or specificity when interpreting the results of experimental and clinical studies. 3 A recent consensus statement aimed to unify definitions and classifications of neurologic injury after aortic arch surgery. 4

Coronary Artery Bypass Grafting With and Without Manipulation of the Ascending Aorta: A Network Meta-Analysis

A 53-year-old female presented with sudden onset of left calf pain eight months following a Bentall procedure for streptococcus endocarditis. She was on Warfarin following surgery. Her foot was cool with absent pulses and an INR was within therapeutic range. A computed tomography (CT) angiogram demonstrated occlusion of the popliteal artery just proximal to the trifurcation secondary to a radio-opaque foreign body (FB) (Figure 1). An X-ray confirmed a radio-opaque ring-like FB (Figure 2). The popliteal artery was explored and a soft plastic ring was retrieved from the arteriotomy using a Fogarty embolectomy catheter (Figure 3). The FB was consistent with a flange from an aortic cannula (Elongated One-Piece Arterial Cannula, Medtronic, Minneapolis, MN, USA). The patient tolerated the procedure well and was discharged with a viable leg and easily palpable distal pulses. Surgeons should be aware of this potential complication when removing this arterial cannula.