Background and Aims There are several complications associated with hemodialytic vascular that arise from the incorrect cannulation, including aneurysms, infection, vessel damage, and uncontrolled bleeding. These risks severely limit treatment opportunities for self-cannulation by patients, which is necessary step for home hemodialysis. To improve quality of life and reduce complications, we developed a novel access port, called Safe Entry Port for AV fistuLae (SEAL), that integrates with fistulae, guides cannulation, and uses an internal colinear valve to prevent aneurysms with minimal risk of back-bleeding and infections (Figure 1A-C). Method The device was additively manufactured using direct metal laser sintering of FDA-approved Ti-6Al-4V. It was then polished and coated with silver-doped titanium nitride (TiN/Ag). The operation of the valve was tested in a mock circulation system using a peristaltic pump and Tyvek tubing to produce a pulsatile hydrostatic pressure gradient. The antimicrobial properties of the valve coating were evaluated in vitro against biofilm formation using standard assays for bacterial spreading area and turbidity. A custom computer-controlled robotic cannulation system was created to fatigue test the port as well as to determine the needle force required to open the valve. Finally, the device was implanted subdermally on a mature brachiocephalic arteriovenous fistula of an adult sheep and cannulated biweekly for six weeks. Device integration and host tissue reaction were evaluated using standard histopathological methods and micro-CT scanning. Results SEAL is engineered to integrate directly over a fistula via a Ti matrix (a mesh of small holes covering the sides of the device for interaction with host tissue). No fluid leaked through the valve during in vitro testing even under physiologically high circulatory pressure. In repeated cannulations of the device during ex vivo simulations with 14G dialysis needles, the peak force required to engage the valve recorded in our dialysis fatigue cycling simulation was 160.5 $ \pm $ 0.02 mN (Figure 1D, E). The device withstood cannulation cycles equivalent to 14 years of dialysis. Furthermore, the colinear valve smoothly opened for continuous flow through the needle guide (Figure 1F-I) and closed automatically under the tensile force similar to that of subcutaneous tissue. Antimicrobial TiN/Ag coating showed significant reduction in bacterial growth in both biofilm assays (Figure 1J,K). In preclinical trials, no signs of infection or backbleeding were observed during the continuous six-week cannulation period; vascular access was continuous with no resistance or complications. Conclusion We show that SEAL nearly eliminates backbleeding risk both in vitro and in vivo. The TiN/Ag coating of the colinear valve significantly limits bacterial biofilm formation ex vivo. Preclinical studies in the sheep model show that the device implanted on a mature fistula can easily be cannulated twice a week without any infection, cannulation complications, or backbleeding for an extensive period. SEAL has the potential to change the future of dialysis treatments, improve the quality of life for patients due the reduction of complications, and allow improved access to home hemodialysis.

Ischemic myocardial disease is a major cause of death among humans worldwide; it results in scarring and pallor of themyocardium and triggers an inflammatory response that contributes to impaired left ventricular function. This response includes and is evidenced by the production of several inflammatory cytokines including TNFα, IL1β, IL4, IFNγ, IL10 and IL6. In the current study, myocardial infarcts were induced in 6 mo old male castrated sheep by ligation of the left circumflex obtuse marginal arteries (OM 1 and 2). MRI was used to measure parameters of left ventricular function that include EDV, ESV, EF, SVI, dp/dt max and dp/dt min at baseline and at 4 wk and 3 mo after infarct induction. We also measured serum concentrations of an array of cytokines. Postmortem histologic findings corroborate the existence of left ventricular myocardial injury and deterioration. Our data show a correlation between serum cytokine concentrations and the development of myocardial damage and left ventricular functional compromise.

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In humans, cardiovascular disease (CVD) is the most frequent cause of death worldwide. Myocardial infarction (MI) is a leading cause of heart failure due to myocardial impairment, yet the progression of the resultant dysfunction is often undetected after incidental or induced myocardial infarction. In this study we tracked the progression of left-sided heart failure in 6-mo-old male castrated sheep in which we created 2 models of myocardial infarction, small and large. Myocardial infarction was induced through ligation of a single branch (obtuse marginal [OM] 1) of the left circumflex coronary artery to create small (mild) infarcts and of 2 branches (OM1 and OM2) for large (severe) infarcts. Progression of heart failure was evaluated by assessing scar size, the left ventricular ejection fraction, hematology, cardiac serum biochemical biomarkers, ST elevation, and clinical observation. All parameters were assessed at baseline and at 3 wk and 3 mo after infarction, except that clinical observation of the animals was conducted daily. The different parameters differed in their usefulness: some verified appropriate creation of the model, whereas others enabled assessment of the progression of heart disease. We hypothesize that myocardial scar size, as a function of induced ischemia, coupled with left ventricular ejection fraction are predictive indicators of postinfarction cardiac dysfunction.