710 research outputs found
Glands of Moll: History, Current Knowledge and Their Role in Ocular Surface Homeostasis and Disease
No full textOver the last 20 years, research into the Meibomian glands of the eyelids has increased exponentially and is now widely recognized as a field of research. It is all the more astonishing that knowledge about another type of gland in the eyelids, the Moll glands or ciliary glands, has almost stagnated and there has been little to almost no progress, even though this type of gland as a whole takes up a relatively large volume in the upper and lower eyelids. There is not much information about the namesake Moll or the function of the glands although these are listed in nearly every textbook of anatomy, histology and ophthalmology. For this reason, we set out to compile the existing knowledge about the Moll glands of the eyelids in order to create a basis for follow-up studies and to stimulate research into this type of gland. In our literature research, we went back to the middle of the 19th century and made contact with a descendant of the Moll family and illustrate their relevance for the present. The structure of the secretory part of the Moll glands is very well described, a number of secretory products are known, but the current state of research allows only very rough speculations about their function. The overview provides numerous interesting insights, which, however, raise more questions than they provide answers
Computational Fluid Dynamics in Descending Thoracic Aortic Aneurysm: Tortuosity Associated With High Displacement Forces
No full textTortuosity comes with higher displacement forces in the aorta. As the descending thoracic aorta (DTA) is becoming longer and more tortuous with age, it is important to understand the influence of tortuosity on displacement forces in the DTA
TCT-781 Thoracic Endovascular Repair Decreases Longitudinal Aortic Distensibility: Experimental Study in an Ex-Vivo Porcine Model
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Mechanochemical endovenous ablation and new frontiers in venous intervention
No full textVenous insufficiency of the lower extremities is a common condition and related to various symptoms, including venous ulcers. The effect of venous insufficiency on patients’ health-related quality of life is substantial and comparable with other chronic diseases such as arthritis, diabetes, and cardiovascular disease. Superficial venous reflux, to a greater or lesser extent, will develop in approximately 40% of women and 20% of men during their lifetime. Until the 1990s, high ligation combined with surgical stripping was the gold standard in the treatment of venous insufficiency. Since then, new endothermal techniques, as endovenous laser or radiofrequency ablation, have revolutionized the standard of care, due to their excellent results. To minimize damage of surrounding tissue, tumescent anaesthesia is necessary in these techniques. Nonetheless, heat-related complications, such as prolonged pain or nerve injury, may still occur. Mechanochemical endovenous ablation (MOCA) is a innovative technique, combining mechanical abrasion of the endothelium with simultaneous infusion of sclerosant. Because MOCA is a non-thermal technique, the need for tumescence and heat-related complications are abolished. The first part of this thesis is dedicated to studying MOCA. A general overview on MOCA is provided including results of a systematic review of literature. The first results of MOCA in the great (30) and small (50) saphenous veins are evaluated and showed that MOCA is feasible, safe and effective. MOCA treatment leads to excellent short term anatomical and clinical success rates. Partial or complete recanalization might occur in around 10% of cases. A study in 68 patients treated with MOCA (34) or RFA (34), showed that MOCA is associated with significantly less postoperative pain. Early quality of life scores improved in both groups. Due to the anatomical proximity of the sural nerve the treatment of small saphenous veins (SSVs) is known for an increased change of nerve injury. A systematic review and meta-analysis on the treatment of SSVs showed that endothermal ablation leads to the best anatomical success rates. The risk of nerve injury is significant. Although the MOCA technique theoretically should minimize the risk for major complications, the available data was not sufficient to draw conclusions on the role of MOCA in SSV. A protocol for a RCT studying MOCA in SSV compared to endothermal ablation is included in this thesis. The second part of the thesis contains 3 studies on innovations in venous intervention. The first reports on the results of laser ablation in insufficient perforator veins, showing it to be feasible and safe. The anatomical success rate is highly dependable on the amount of energy delivered. The second evaluated a new percutaneous venous closure device, to place a keyring-shape implant around the target vein. Although results are promising, future developments regarding sizing, applications of biomaterials and increasing accuracy in positioning are essential. The final study describes a new deep venous valve concept. Whereas previous valve designs were hampered with thrombotic occlusion, the current single, "spinnaker-shaped" leaflet functioned well and remained patent in a short-term animal experiment. Future studies regarding optimizing leaflet material or coating are on-going
Periprocedural antithrombotics in arterial procedures: The road to consensus ...
No full textIn 1940 Murray published his paper on the role of “heparin in surgical treatment of blood vessels”. The introduction of heparin as a prophylactic antithrombotic in vascular surgery increased surgical interventions in the arterial circulation. Heparin reduces clotting of blood while clamping arteries and thereby reduces thrombo-embolic complications, local and systemic. Heparin is also considered essential during percutaneous endovascular interventions with balloons and stents. Heparin has a major, clinical, disadvantage: the prolonged clotting of blood causes an increase in bleeding complications, such as more blood loss and more blood transfusions. This also increases procedure time, leading to more (infectious) complications. The use of heparin can also lead to the development of heparin induced thrombocytopenia (HIT) syndrome, an unpredictable response of the immune system on the administration of heparin, possibly resulting in arterial and venous thrombo-embolic complications. Another major disadvantage of the use of heparin is the fact that heparin has no linear dose-response curve. This results in an unpredictable therapeutic effect in at least 20% of patients. This underlines the necessity of performing measurements of the actual effect of heparin, also because heparin is used worldwide in all open and endovascular arterial procedures. To develop new, evidence based guidelines for vascular surgery and interventional radiology (IR), a study group was instituted in the Netherlands (CAPPA: Consensus on Arterial PeriProcedural Anticoagulation). This study group performed 2 surveys on anticoagulation amongst Dutch vascular surgeons and IR. Results showed variation on the use of anticoagulation before, during and after arterial open and endovascular procedures. Predominantly heparin was used by most surgeons and IR during procedures as an prophylactic antithrombotic but the applied doses varied importantly. Also for IR, the variety found for the use of heparin in the Netherlands, was not the same as the variety found in the United Kingdom. Systematic reviews of literature on the use of heparin by vascular surgeons during open abdominal aortic aneurysm repair (AAA) and infra-inguinal bypass surgery (IABS) showed not much evidence for the beneficiary effect of heparin. During open AAA repair a trend was observed to harmful side effects such as more blood loss, longer operation time and more blood transfusion when heparin was used. Thrombo-embolic complications were not increased when no heparin was used. In the Netherlands a trial was performed to compare open and endovascular repair op AAA (DREAM trial). A sub-analysis from this trial in the open repair group showed no clinical differences in outcomes when heparin or no heparin was administered. The CAPPA group designed a randomized controlled trial (RCT) on the use of heparin during open AAA repair. Patients will be randomized to a heparin and a no-heparin group. Aim of this NANDA? trial (No Anticoagulation Needed During open AAA repair?), will be to determine if heparin is beneficial as an prophylactic antithrombotic. Multiple other trials on IABS and endovascular interventions are developed. Ultimate goal of these trials will be to create consensus and new guidelines on periprocedural prophylactic antithrombotics in arterial vascular surgery and IR
Stent-Graft Deployment Increases Aortic Stiffness in an Ex Vivo Porcine Model
No full textBackground Aortic stiffness is an independent predictor of cardiovascular mortality. In this study, the effect of thoracic endovascular aortic repair (TEVAR) on aortic stiffness is investigated by measuring aortic pulse wave velocity (PWV) in an ex vivo porcine model. Methods Fifteen fresh porcine thoracic aortas were connected to a benchtop pulsatile system. Intraluminal pressures were recorded in the ascending aorta and at the celiac trunk using a needle connected to a pressure sensor. The distance between the needles was divided by the time difference between the base of the pressure peaks to calculate aortic PWV at baseline and after stent-graft deployment and distal stent-graft extension. Results Mean aortic PWV was 5.0 m/s at baseline. PWV increased by 4% after proximal stent-graft deployment (P = 0.09) and by 18% after stent-graft extension (P < 0.001). Pulse pressure in the nonstented ascending aorta increased by 11.0 ± 1.2 mm Hg after proximal stent-graft deployment (P < 0.001) and by 17.3 ± 1.5 mm Hg after stent-graft extension (P < 0.001). The increases in PWV and pulse pressure showed a positive linear correlation with the percentage of stent-graft coverage (P < 0.001 and P < 0.001). Conclusions In this experimental setup, aortic stiffness increased after stent-graft deployment, dependent on the percentage of the aorta that was covered by stent graft. These results show that TEVAR leads to significant changes in aortic hemodynamics, which merits evaluation in the clinical setting
Near-infrared spectroscopy and its potential in diagnosis of vascular disease: Translational research and clinical applications
No full textNear-infrared light is already successfully used for a variety of applications in medical health care, such as pulse oximetry, optical coherence tomography, and near-infrared fluorescence. This thesis examines the potential of near-infrared light used by NIRS in the detection of (patho)physiological consequences of vascular disease. It was shown that NIRS can be used in a clinical setting for the assessment of chronic compartment syndrome of lower extremities, and as a surveillance tool for detection of free flap failure. Also, NIRS measurements in muscle tissue have the potential to become an accepted diagnostic tool in other vascular diseases. However, with the current knowledge regarding NIRS, additional validation is needed before routine use of NIRS in the diagnosis of critical limb ischemia, spinal cord ischemia in thoracoabdominal aortic aneurysm repair, and renal allograft ischemia in patients undergoing kidney transplantatio
ePTFE covered stents in occlusive SFA disease: clinical and experimental studies
No full textPeriferal arterial occlusive disease (PAOD) is an affliction that affects up to 20% of patients over the age of 60 (1). It is defined as atherosclerosis caudal of the aortic bifurcation resulting in Intermittent Claudication. This in turn is defined as reproducible muscle pain of the lower extremities due to impairment of oxygenation during exercise (therapy). The Fontaine grading system is based on these clinical features and is administered, together with other classification systems to assess the severity of this affliction. Some 25% of patients develop progression of these symptoms, where critical limb ischaemia is manifested in 0,025% in a normal population (2) requiring some form of surgery or intervention. Although bypass surgery is still a key component in the treatment of tissue loss in patients with critical limb ischaemia, we can see that endovascular techniques are increasingly administered and in some instances taking over the role of bypass surgery. This is not only due to quality improvements of stents, stent grafts and techniques, but also because it needs less extensive surgery. Over the past decade we have seen a gradual improvement of medium and long-term patency results of endovascular procedures (3,4,5). The critically ill patient does not necessarily need to be hospitilized for longer periods of time with complications that go with it, not to mention the costs. Since some 55% of patients diagnosed with Chritical Limb ischaemia will die the first 2 year, treatment should not only focus on risk factor treatment but also on quality of life in short and long term by preventing limb loss (6). Thus, in the aim to do just that in these patients one should investigate whether these were durable techniques for lower limb ischaemia. General aims of this thesis The aim of this thesis is to report on the currently available knowledge on results in bypass surgery, particularly focussing on complication rates over the last decade. The aim is also to look into our Superficial Femoral Artery (SFA) endovascular treatment results of occlusive disease. In the latter we focus on the role and significance of collateral system flow and its relevance in clinical decision making
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