Lesion Eccentricity Plays a Key Role in Determining the Pressure Gradient of Serial Stenotic Lesions: Results from a Computational Hemodynamics Study.

PURPOSE: In arterial disease, the presence of two or more serial stenotic lesions is common. For mild lesions, it is difficult to predict whether their combined effect is hemodynamically significant. This study assessed the hemodynamic significance of idealized serial stenotic lesions by simulating their hemodynamic interaction in a computational flow model. MATERIALS AND METHODS: Flow was simulated with SimVascular software in 34 serial lesions, using moderate (15 mL/s) and high (30 mL/s) flow rates. Combinations of one concentric and two eccentric lesions, all 50% area reduction, were designed with variations in interstenotic distance and in relative direction of eccentricity. Fluid and fluid-structure simulations were performed to quantify the combined pressure gradient. RESULTS: At a moderate flow rate, the combined pressure gradient of two lesions ranged from 3.8 to 7.7 mmHg, which increased to a range of 12.5-24.3 mmHg for a high flow rate. Eccentricity caused an up to two-fold increase in pressure gradient relative to concentric lesions. At a high flow rate, the combined pressure gradient for serial eccentric lesions often exceeded the sum of the individual lesions. The relative direction of eccentricity altered the pressure gradient by 15-25%. The impact of flow pulsatility and wall deformability was minor. CONCLUSION: This flow simulation study revealed that lesion eccentricity is an adverse factor in the hemodynamic significance of isolated stenotic lesions and in serial stenotic lesions. Two 50% lesions that are individually non-significant can combine more often than thought to hemodynamic significance in hyperemic conditions.

The Supera Interwoven Nitinol Stent as a Flow Diverting Device in Popliteal Aneurysms.

PURPOSE: The feasibility of using a compressed interwoven Supera stent as a flow diverting device for popliteal aneurysms was recently demonstrated in patients. It is unclear, however, what the optimal flow diverting strategy is, because of the fusiform shape of popliteal aneurysms and their exposure to triphasic flow. To assess this flow diverting strategy for popliteal aneurysms, flow profiles and thrombus formation likelihood were investigated in popliteal aneurysm models. MATERIALS AND METHODS: Six popliteal aneurysm models were created and integrated into a pulsatile flow set-up. These models covered a bent and a straight anatomy in three configurations: control, single-lined and dual-lined Supera stents. Two-dimensional flow velocities were visualized by laser particle image velocimetry. In addition, the efficacy of the stent configurations for promoting aneurysm thrombosis was assessed by simulations of residence time and platelet activation. RESULTS: On average for the two anatomies, the Supera stent led to a twofold reduction of velocities in the aneurysm for single-lined stents, and a fourfold reduction for dual-lined stents. Forward flow was optimally diverted, whereas backward flow was generally deflected into the aneurysm. The dual-lined configuration led to residence times of 15-20 s, compared to 5-15 s for the single stent configurations. Platelet activation potential was not increased by the flow diverting stents. CONCLUSION: A compressed Supera stent was successfully able to divert flow in a popliteal aneurysm phantom. A dual-lined configuration demonstrated superior hemodynamic characteristics compared to its single-lined counterpart.

Validation of Central Pressure Estimation in Patients with an Aortic Aneurysm Before and After Endovascular Repair.

PURPOSE: The aim of this study was to investigate if non-invasive central pressure estimations are accurate in patients with an abdominal aortic aneurysm, before and after endovascular repair. Secondary evaluation was if measurement-accuracy was dependent on anatomical characteristics. METHODS: Procedural invasive and non-invasive pressure-measurements were performed simultaneously both before and after endovascular repair in 20 patients with an infrarenal abdominal aortic aneurysm. Invasive catheter measurements were performed in the abdominal aorta. A tonometric device was used to perform non-invasive pressure-wave-analysis at the radial artery. A generalized transfer-function was used to generate an ascending aortic waveform for both measurements, allowing for direct comparison. RESULTS: Pre-treatment the mean differences between methods were - 5.5 mmHg (p = .904), - 11.8 (p < .001), and - 7.2 mmHg (p = .124) for central systolic, diastolic, and mean pressure, respectively. The accuracy was dependent of aneurysm sac volume and intraluminal thrombus volume. Post-treatment limits of agreement were smaller for all pressure parameters compared to pre-treatment. The mean differences were 6.5 mmHg (p = .007), - 6.4 (p < .020), and 1.6 mmHg (p = .370) for central systolic, diastolic, and mean pressure, respectively. CONCLUSION: In untreated AAA's the accuracy of non-invasive central pressure estimation was acceptable (mean difference between 5 and 10 mmHg) when compared to invasive pressures, but dependent of AAA characteristics. After EVAR the accuracy of central pressure estimation improved (reduction of 75% of the mean difference between pre and post measurements) TRIAL REGISTRATION NUMBER: NCT03469388; 3-5-2018.

Time intervals between semen production, initiation of analysis, and IUI significantly influence clinical pregnancies and live births.

PURPOSE: Does IDEF mapping help monitor the technical process of IUI and explore the potential improvements which might contribute to increased pregnancy and live birth rates? METHOD: Retrospective analysis of 1729 homologous IUI cycles of couples attending a fertility clinic in a university hospital setting. Standardized conventional semen parameters were analyzed and the semen samples prepared via discontinuous density gradient centrifugation. RESULTS: There was no significant association between sperm concentration, motility and morphology (analysis phase), and pregnancy outcome. Only female and male ages were significantly associated with the pregnancy outcome. There was a significant difference in the odds on clinical pregnancies and live births when analysis was ≤ 21 min initiated, and < 107 min between sample production and IUI, adjusted for male and female age. CONCLUSIONS: Adjusting for the couple's age, we could show that time intervals between semen production and analysis and IUI when kept low significantly influenced clinical pregnancies and live births.

New diagnostic and treatment strategies in renal artery stenosis: a promising pursuit or disappointment foretold?

Clinical management of renal artery stenosis has seen a major shift, after randomised clinical trials have shown no group benefit of endovascular intervention relative to optimal medical control. However, the inclusion criteria of these trials have been criticised for focusing on a subset of patients with atherosclerotic renal artery stenosis where intervention was unlikely to be beneficial. Moreover, new imaging and computational techniques have become available, which have the potential to improve identification of patients that will respond to interventional treatment. This review addresses the challenges associated with clinical decision making in patients with renal artery stenosis. Opportunities for novel diagnostic techniques to improve patient selection are discussed, along with ongoing Dutch studies and network initiatives that investigate these strategies.

Solid contact potassium selective electrodes for biomedical applications - a review.

Ion-selective electrodes (ISE) are used in several biomedical applications, including laboratory sensing of potassium concentration in blood and urine samples. For on-site determination of potassium concentration and usage in other applications such as determination of extracellular potassium concentration, miniaturization of the sensors is required. To that extent, solid contacts have proven to be an adequate substitute of liquid contacts as inner layer for ion-to-electron transduction, allowing industrial production of miniaturized ISEs. This review paper covers relevant developments of solid-state ISEs in the past decade, critically compares current potassium ISEs and discusses future prospects for biomedical applications. Performances of three main types of solid contact materials in potassium sensing are compared, namely polypyrrole, polythiophenes and conducting nanomaterials. With these new materials, numerous improvements in stability, selectivity and time response of solid-state ISEs have been made. Current developments are new operational methods of sensing, flexible miniaturized sensors and multi-electrode designs able to measure electrolyte concentrations in one-drop blood samples or transmembrane ionic flows.

[Treatment of multiple metacarpal (tarsal) fractures using a brace in 2 foals and a calf]. / De behandeling van meervoudige metacarpale (-tarsale) fracturen met een loopbeugel bij twee veulens en een kalf.

The placement of a brace for external fixation of multiple fractures of the carpus or tarsus is described. In these two foals and calf we succeeded in obtaining a combination of good immobilization and full loading of the affected leg.

[Preliminary experience with a buffy coat analyser in horses]. / Voorlopige ervaring met een buffy coat-analyser bij paarden.

The present author's practice was offered the opportunity of testing a so-called buffy-coat analyser of the firm of Becton & Dickinson for its use in the field. He does not deny readers the report of his preliminary experience. In addition, the interpretation of the results and the limitations of the apparatus are briefly discussed.