An in vitro study to optimise treatment of varicose veins with radiofrequency-induced thermo therapy

2014 ◽  
Vol 30 (1) ◽  
pp. 17-23 ◽  
Author(s):  
George E Badham ◽  
Sophie M Strong ◽  
Mark S Whiteley
Keyword(s):  
Thermal Ablation ◽  
Varicose Veins ◽  
Video Recording ◽  
In Vitro Study ◽  
Porcine Liver ◽  
Vein Wall ◽  
High Impedance ◽  
Liver Model ◽  
Thermal Spread

Objective To develop a reproducible method of using radiofrequency-induced thermotherapy with adequate thermal spread to ablate the whole vein wall in a truncal vein but avoiding carbonisation, device sticking and high impedance “cut outs” reducing interruptions during endovenous treatments. Methods Porcine liver was treated with radiofrequency-induced thermotherapy under glass to allow measurements, observation and video recording. Powers of 6–20 W were used at varying pullback speeds to achieve linear endovenous energy densities of 18–100 J/cm. Thermal spread, carbonisation of treated tissue and high-impedance cut outs were recorded. Results The currently recommended power settings of 18 and 20 W produced sub-optimal results. If pulled back at 3 s/cm to achieve linear endovenous energy densities around 60 J/cm, tissue carbonisation and high impedance cut outs occurred. When high powers and fast pullbacks of 1 s/cm were used, no carbonisation or cut outs occurred but thermal ablation of the liver model was below target due to reduced time for thermal conduction. Low powers (6–12 W) with slow pullbacks (6–12 s/cm) achieved target thermal ablation with minimal carbonisation and high impedance cut outs. Conclusions Using low power (6 W) and a slow discontinuous pullback (6 s every 0.5 cm, in steps), we were able to achieve our target thermal ablation in the porcine liver model without carbonisation and high impedance cut outs. This suggests the currently recommended power levels could be reduced, reducing the need to remove the device to clean the electrodes during treatment while achieving target thermoablation of the treated tissue.

Pattern of thermal damage and tissue carbonisation from endovenous radiofrequency ablation catheter – Using an in vitro porcine liver model

2020 ◽  
pp. 026835552097553
Author(s):  
Emma B Dabbs ◽  
Max I Riley ◽  
Charlotte E Davies ◽  
Olivia H Bishop ◽  
Mark S Whiteley
Keyword(s):  
Thermal Damage ◽  
Lateral Spread ◽  
Porcine Liver ◽  
Vein Wall ◽  
Lower Power ◽  
Damage Area ◽  
Energy Delivery ◽  
Liver Model ◽  
Thermal Spread

Background Successful endovenous thermoablation relies on transmural vein wall ablation. We investigated the pattern of thermal spread and tissue carbonisation from RadioFrequency-induced ThermoTherapy (RFiTT) at different powers and pull back methods, using a porcine liver model. Methods We used a previously validated in-vitro porcine liver model. Different powers from 5–25 W were used to administer 150 J. We compared continuous and pulsed energy delivery. Length, lateral spread, and total area of thermal damage, together with any tissue carbonisation, was measured using digital analysis software. Results All experiments used 150 J total energy. Total thermal damage area was smaller with lower power and pulsed energy. Continuous energy caused more tissue carbonisation than pulsed except at 25 W. Conclusion Reduced thermal damage with lower power or pulsed energy results from cooling due to increased time of treatment. Increasing the power increases tissue carbonisation. Optimal treatment is determined by the highest power used continuously that does not cause tissue carbonisation.

Electro-physiological parameters of hepatic radiofrequency ablation—a comparison of an in vitro versus an in vivo porcine liver model

2009 ◽  
Vol 394 (3) ◽  
pp. 503-509 ◽  
Author(s):  
R. Wahba ◽  
C. Bangard ◽  
R. Kleinert ◽  
S. Rösgen ◽  
J.-H. Fischer ◽  
...  
Keyword(s):  
Radiofrequency Ablation ◽  
Physiological Parameters ◽  
Porcine Liver ◽  
Liver Model

The venous valve agger and plasma noradrenaline-mediated venodilator feedback

2007 ◽  
Vol 22 (3) ◽  
pp. 116-130 ◽  
Author(s):  
T P Crotty
Keyword(s):  
Saphenous Vein ◽  
Varicose Veins ◽  
Feedback Effect ◽  
Venous Valve ◽  
Venous Tone ◽  
Vein Wall ◽  
University Departments ◽  
Perfusion Studies

Objective: To investigate the structure and function of the venous valve agger, a fibroelastic structure located at the base of every valve in veins that are responsive to noradrenaline (NA). Design: Constant flow perfusion studies of the responses of in situ and in vitro canine lateral saphenous vein segments to NA and electrical stimulation, supplemented by histological studies of the segments. Setting: University Departments of Physiology and Histology. Materials: Segments of canine lateral saphenous vein. In vitro = 84, in situ = 60 plus. Results: The agger is a crescentic fibroelastic sleeve, spanning the vein wall very obliquely through which the local vasa venarum network drains. It has a dedicated musculature which, when the tone rises, contracts and stretches the fibroelastic of the agger and opens the drainage channels to reflux. Each agger has four muscles, two each of which insert on the concave and convex margins of the agger. They pull in opposite directions when they contract. Conclusions: The agger forms part of a complex that, in conjunction with its dedicated musculature, a reversible transmural pressure gradient and physiological turbulence in the valve sinuses, positively facilitates drainage from the local segment of the vasa venarum network when venous tone is normal; and when venous tone is elevated it pumps and sucks blood from the lumen of the vein to perfuse the vasa venarum network. When the plasma NA in the perfusate diffuses from the network, it causes a localized venodilator feedback effect that restores the elevated tone of the vein to normal. The feedback effect is potent, being estimated to reduce the venonstrictor effect of neuronal NA by about 50% when flow is laminar and considerably more when flow is turbulent. There is evidence that plasma NA may constitute the lateral inhibitory component of the NA chemostimulus of the smooth muscle cell, neuronal NA constituting the excitor component. A chronic breakdown in agger function is believed to be the cause of varicose veins.

Guidelines of the First International Consensus Conference on Endovenous Thermal Ablation for Varicose Vein Disease – ETAV Consensus Meeting 2012

2014 ◽  
Vol 30 (4) ◽  
pp. 257-273 ◽  
Author(s):  
Miloš D Pavlović ◽  
Sanja Schuller-Petrović ◽  
Olivier Pichot ◽  
Eberhard Rabe ◽  
Uldis Maurins ◽  
...  
Keyword(s):  
Thermal Ablation ◽  
Task Force ◽  
Varicose Veins ◽  
Consensus Meeting ◽  
International Consensus ◽  
Vein Wall ◽  
Thermal Methods ◽  
Quality Of Evidence ◽  
Endovenous Thermal Ablation

Aim: Endovenous thermal ablation (ETA) procedures are catheter-directed, ultrasound (US)-guided thermal methods for treatment in varicose veins disease. Radiofrequency, laser or steam energy thermally denatures vein wall collagen, leading first to vein wall inflammation, then fibrosis and finally to occlusion. The aim of this guideline is to give evidence-based recommendations for ETA procedures. Methods: These guidelines were drafted during a consensus meeting of a group of experts in the field of ETA in June 2012 (Hvar, Croatia) under the auspices of the International Union of Phlebology (IUP). These guidelines review the present state of knowledge as reflected in peer-reviewed published medical literature. The recommendations of these guidelines are graded according to the American College of Chest Physicians Task Force recommendations on Grading Strength of Recommendations and Quality of Evidence in Clinical Guidelines. Results: Recommendations on the use of ETA procedures were made based on the quality of evidence for efficacy, safety, tolerability, cosmetic outcome, patient satisfaction/preference and, where appropriate, on the experts' opinion. Health economics were not considered, since differences in national health systems and pricing make it difficult to form general conclusions that are relevant at an international level.

scholarly journals Vitrectomy-Assisted Biopsy: An in vitro Study on the Impact of Cut Rate and Probe Size

2021 ◽  
pp. 1-7
Author(s):  
Erlend Ulltang ◽  
Jens Folke Kiilgaard ◽  
Nazanin Mola ◽  
David Scheie ◽  
Steffen Heegaard ◽  
...  
Keyword(s):  
In Vitro Study ◽  
Probe Type ◽  
Porcine Liver ◽  
Probe Diameter ◽  
Intraocular Tumors ◽  
Probe Size ◽  
23 Gauge ◽  
The Impact ◽  
Conventional Light Microscopy

<b><i>Purpose:</i></b> The aim of this study was to optimize the technique of performing vitrectomy-assisted biopsy of intraocular tumors by comparing the cytohistological findings in specimens obtained with different vitrectomy probes and cut rates. <b><i>Methods:</i></b> Vitrectomy-assisted biopsies were taken from a fresh porcine liver. For each sampling, the vacuum level was 300 mm Hg. The following parameters were compared; cut rate (60, 600 and 6,000 cuts per minute [cpm]), probe type (standard and two-dimensional cutting [TDC]), and probe diameter (23-gauge and 25-gauge). The specimens were assessed by automated whole-slide imaging analysis and conventional light microscopy. <b><i>Results:</i></b> Seventy-two biopsies were analyzed for the number of hepatocytes, total area of tissue fragments, and total stained area of each microscope slide. For all probe types, these parameters were significantly and positively correlated with the cut rate. TDC probes led to significantly higher scores than those of standard probes, independent of the cut rate. There were no significant differences in results when using 23-gauge or 25-gauge standard probes. Light microscopic examination demonstrated well-preserved cells sufficient for cytohistological analyses in all investigated cases. <b><i>Conclusions:</i></b> The higher the cut rate, the larger is the amount of aspirated cellular material. There were no significant differences between 23-gauge and 25-gauge biopsies. Cut rates up to 6,000 cpm did not adversely affect the cytohistological features of the samples.

scholarly journals In Vivo and In Vitro Assessment of Human Saphenous Vein Wall Changes

2007 ◽  
Vol 1 (1) ◽  
pp. 15-21 ◽  
Author(s):  
Akram M Asbeutah ◽  
Sami K Asfar ◽  
Hussain Safar ◽  
Mabayoje A Oriowo ◽  
Ihab ElHagrassi ◽  
...  
Keyword(s):  
Saphenous Vein ◽  
Varicose Vein ◽  
Varicose Veins ◽  
Maximum Response ◽  
Repeated Measure ◽  
Maximum Diameter ◽  
Vein Wall ◽  
Post Surgery ◽  
Significant Difference

Purpose: To investigate if noradrenaline (NA) and 5-hydroxyptamine (5-HT) drugs induce responses of isolated control and varicose veins are altered by removal of the endothelium. Subjects & Methods: Specimens of the great saphenous vein (GSV) were obtained from 12 subjects with primary varicose veins and 12 subjects from donor vessels at cardiac surgery. A total of 10 normal healthy volunteers were selected for comparison. The diameter changes of GSV during the resting phase, at the end of 5 minutes occlusion, and then every 30 seconds post deflation for five minutes were measured using B-mode ultrasound. Post-surgery the vein sample was collected in a tube of Krebs-Henseleit solution. Results: The repeated measure ANOVA test for the diameter, percent, and difference changes of GSV diameter from maximum diameter at different time intervals showed significance difference within and between all groups. NA and 5-HT produced concentration-dependent contractions of control and varicose saphenous vein segments. There was no significant difference in the potency of NA and for 5-HT, but the maximum response, normalized for tissue weight, was less in varicose vein segments. Removal of the endothelium had no effect on the potency of NA or 5-HT but significantly (p<0.05) reduced the maximum response to NA and 5-HT in varicose vein segments but not to 5-HT in control veins. Conclusion: The venous endothelial damage may cause vascular smooth muscle contractions dysfunction that favours dilatation and secondary valvular insufficiency.

A Novel Endoluminal Technique for Varicose Vein Management: The VNUS Closure

2001 ◽  
Vol 16 (4) ◽  
pp. 145-148 ◽  
Author(s):  
N. Fassiadis ◽  
B. Kianifard ◽  
J. M. Holdstock ◽  
M. S. Whiteley
Keyword(s):  
Varicose Veins ◽  
Saphenous Nerve ◽  
Full Thickness ◽  
Nerve Injuries ◽  
Vein Wall ◽  
The Past ◽  
Long Saphenous Vein ◽  
Computer Feedback ◽  
Thickness Skin ◽  
Thermal Spread

In an attempt to reduce the morbidity of high tie and strip of the long saphenous vein various extraluminal and intraluminal electrosurgical devices have been employed in the past using monopolar energy to ablate varicose veins. As result of this full-thickness skin burns and saphenous nerve injuries were observed by surgeons using these techniques. This report describes the VNUS Closure, a novel endovascular computer-feedback-controlled application of bipolar electrothermal energy which ensures transmural heating of the vein wall while minimising thermal spread to neighbouring tissues.

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