Physics-based virtual environment for training core skills in vascular interventional radiological procedures.

Recent years have seen a significant increase in the use of Interventional Radiology (IR) as an alternative to open surgery. A large number of IR procedures commences with needle puncture of a vessel to insert guidewires and catheters: these clinical skills are acquired by all radiologists during training on patients, associated with some discomfort and occasionally, complications. While some visual skills can be acquired using models such as the ones used in surgery, these have limitations for IR which relies heavily on a sense of touch. Both patients and trainees would benefit from a virtual environment (VE) conveying touch sensation to realistically mimic procedures. The authors are developing a high fidelity VE providing a validated alternative to the traditional apprenticeship model used for teaching the core skills. The current version of the CRaIVE simulator combines home made software, haptic devices and commercial equipments.

What is the evidence for the efficacy of cryoplasty?

Cryoplasty is a technique for treating vascular stenosis which combines balloon angioplasty with cold injury. The combination is proposed to reduce the incidence of restenosis by inhibition of neointimal hyperplasia. There have been several clinical studies which purport to show improved patency compared to conventional angioplasty. Unfortunately, these are not comparative or controlled studies and have not been performed, analyzed or reported in accordance with recognized reporting standards for peripheral vascular intervention. The studies on femoropopliteal disease have selected favourable patients. Of greatest concern is the use of surrogate endpoints in lieu of objective demonstration of vessel patency. Critical interpretation of the results fails to demonstrate any convincing superiority of cryoplasty compared to conventional balloon angioplasty. Where little difference in outcome exists between two techniques, a trial comparing them will require hundreds of patients to be sufficiently powered to demonstrate a benefit of one technique over the other. As cryoplasty is significantly more expensive than conventional angioplasty, the cost benefit ratio is unfavourable and such a trial is unlikely to occur. This article is a critical review of the technique of cryoplasty. The reader will be able to: describe expected outcomes from balloon angioplasty; describe the theoretical role for cold injury as a component of angioplasty; recognize the need to adhere to well defined standards when reporting the results of new techniques for treating vascular disease; critically review the results of cryoplasty; understand the limitations and relevance of the published clinical results of cryoplasty.

Cryoplasty--where is the evidence?

Cryoplasty has been proposed as a more effective alternative to conventional percutaneous transluminal angioplasty in the management of peripheral vascular disease. In this review, we critically evaluate the current evidence to determine both the clinical efficacy and the technical issues with cryoplasty.

Cryoplasty for arterial restenosis.

OBJECTIVE: A prospective follow-up study of patients with arterial restenosis undergoing cryoplasty. MATERIALS & METHODS: Between May 2004 and June 2005, 10 patients with restenosis following ilio-femoral endovascular treatment underwent twelve cryoplasty procedures. All patients had had at least one previous episode of stenosis treated by conventional endovascular methods and had suffered further restenosis. The indications for treatment were grafts at risk (n=5) and symptomatic in-stent restenosis (n=5). Two patients underwent re-cryoplasty. Cryoplasty was performed in accordance with manufacturer's instructions using 6-8mm balloons. All patients had Doppler ultrasound evaluation at 1, 3, 6 and 12 months. RESULTS: All procedures had angiographically successful immediate outcome with <30% residual stenosis. Non flow limiting dissection was evident in two cases. In six procedures (50%), restenosis was evident within 6 months post-procedure, whilst in the other six, there was progressive restenosis appearing between 6-12 months. Five cryoplasty procedures have needed endovascular re-intervention due to symptomatic high-grade restenosis and a sixth is awaiting surgery. CONCLUSION: Cryoplasty is of no value in patients with restenosis in the iliofemoral segment with half the procedures failing within six months and all of them within the first year. Evidence to support the use of cryoplasty in the peripheral arterial restenotic lesions is lacking.

Simulators in catheter-based interventional radiology: training or computer games?

Training in interventional radiology (IR) relies on a traditional apprenticeship; to protect patients, expert supervision is mandatory until knowledge, attitudes and practical skills have been certified as satisfactory. However, the current quality of IR training is threatened by reduced time for trainees to learn, as well as a loss of basic diagnostic, training cases to non-invasive imaging. At the same time, IR techniques are becoming a focus of interest to a range of other clinical specialities. To address this training shortfall there is a need to develop novel training alternatives such as simulator models. Few simulator models in any medical field have been successfully validated to show improved clinical skills in treating patients. To date no endovascular simulator has met this standard. A good simulator must be based around key performance measures (metrics) derived from careful analysis of the procedure to be replicated. Metrics can be determined by trained psychologists from a direct analysis of the content of the job or task to be tested. The identification of these critical measures of performance is a complex process which must be tailored to a training curriculum to be effective. Simulators based on flawed metrics will invariably lead to unsatisfactory assessment. It follows that simulator development must involve the statutory licensing authorities. Equally it is essential that we do not assume that training on a particular simulator will correlate with the ability to perform the task in the real world. This "transfer of training" must be rigorously proven by validation studies.

Endovascular embolization of visceral artery aneurysms with ethylene-vinyl alcohol (Onyx): a case series.

We report the application of the liquid embolic agent ethylene-vinyl alcohol (Onyx; MicroTherapeutics, Irvine, CA, USA) in the management of visceral artery aneurysms. The technique and indications for using Onyx are discussed with emphasis on the management of wide-necked aneurysms and maintenance of patency of the parent vessel. None of the cases was considered suitable for stent-grafting or embolization with conventional agents. Two aneurysms of the renal artery bifurcation and one aneurysm of the inferior pancreaticoduodenal artery were treated. Following treatment there was complete exclusion of all aneurysms. There was no evidence of end-organ infarction. Follow-up with intervals up to 6 months has shown sustained aneurysm exclusion. Onyx is known to be effective in the management of intracranial aneurysms. Our experience demonstrates the efficacy and applicability of the use of Onyx in the treatment of complex visceral artery aneurysms.

Current trends in thrombolysis: implications for diagnostic and interventional radiology.

Current trends in thrombolysis are of relevance to both diagnostic and interventional radiologists. In addition to the traditional use of thrombolytic therapy in conditions such as peripheral arterial thrombosis, venous thrombosis and pulmonary embolic disease, more recent interest has focused on the potential use of thrombolysis in acute stroke. There will be significant implications for the provision of radiological services if current trials show a favourable outcome for thrombolysis in stroke. This article looks at a range of conditions in which thrombolysis may be useful, on the strength of currently available evidence. Future trends will depend on the outcomes of the current trials.

Carbon dioxide angiography: a simple and safe system of delivery.

Carbon dioxide (CO2) is an established alternate angiographic contrast agent, which can be delivered by pump or hand injection. We describe a simple, safe and inexpensive hand injection system that delivers a known volume of CO2 at atmospheric pressure and prevents contamination with room air.

Infusion techniques for peripheral arterial thrombolysis.

BACKGROUND: Thrombolytic therapy is a useful tool in the management of acute peripheral arterial ischaemia. Fibrinolytic drugs are used to disperse blood clot to clear arterial occlusion. A variety of techniques are used to deliver these agents. OBJECTIVES: To determine the optimal technique for infusion of fibrinolytic drugs in peripheral arterial ischaemia. SEARCH STRATEGY: The Cochrane Library (issue 3, 2003) and the Specialised Trials Register of the Cochrane Review Group on Peripheral Vascular Diseases (July 2003) were searched. Proceedings from meetings of British, European and North American Vascular Surgical and Radiological Societies, plus reference lists of identified studies were also searched for relevant trials. Major pharmaceutical firms and trialists were asked about unpublished trials. SELECTION CRITERIA: Two reviewers independently selected randomised controlled trials comparing infusion techniques of fibrinolytic agents in the treatment of acute peripheral arterial ischaemia. Trials with poor quality methodology were excluded. DATA COLLECTION AND ANALYSIS: Data from included trials were collated and analysed for the following outcomes: limb salvage, amputation, death, vessel patency, time to achieve thrombolysis, and reduction in the need for surgical intervention. Complication rates were compared for: major haemorrhage, cerebrovascular accident and distal embolization. MAIN RESULTS: Intra-arterial delivery of thrombolytic agents appeared to be more effective than intravenous administration. Thrombolysis was more effective when the angiographic catheter was placed within the thrombus. Although 'high dose' and 'forced infusion' techniques achieved vessel patency in less time than 'low dose infusion', there were more bleeding complications, and no increase in patency rates or improvement in limb salvage at 30 days. REVIEWER'S CONCLUSIONS: Implications for practice Thrombolysis should be reserved for patients with limb threatening ischaemia, due to the high risk of haemorrhage or death. Greater benefit is seen when the thrombolytic agent is delivered into the thrombus. Systemic intravenous thrombolysis is less effective than intra-arterial thrombolysis and is associated with an increase in bleeding complications. 'High dose' and 'forced infusion' techniques, or adjunctive agents such as platelet glycoprotein IIb/IIIa inhibitors may speed up thrombolysis, but these are not accompanied by lower amputation rates or a decreased need for adjunctive endovascular or surgical procedures. 'Low dose continuous infusion', following initial lacing of the thrombus with a high dose of the thrombolytic agent, is the least labour intensive technique. Implications for research Only large multicentre trials with carefully controlled inclusion criteria will be sufficiently powerful to demonstrate genuine benefit for a particular thrombolytic regime.

Endovascular stent-grafts for superficial femoral artery disease: results of 1-year follow-up.

PURPOSE: To document a preliminary study to assess the deployment and outcomes of endoluminal stent grafting in the superficial femoral artery (SFA) with use of a prototype device. MATERIALS AND METHODS: Twenty patients with lifestyle-limiting intermittent claudication were selected for treatment with a balloon-mounted expansive polytetrafluoroethylene graft. All patients had angiographically proven SFA disease (median length, 17 cm) with normal arterial inflow and at least two calf vessels patent to the ankle. Follow-up was by means of ankle brachial pressure index (ABPI), duplex ultrasound, and angiography. RESULTS: Fourteen patients were successfully treated. Six patients were excluded: five by the study protocol and one because the procedure was a technical failure. ABPI rose from 0.6 before treatment to 1.0. The treated limbs became asymptomatic. Twelve-month primary, primary assisted, and secondary patency rates of treated patients were 29%, 50%, and 64%. CONCLUSION: Endovascular stent grafting of SFA lesions is technically feasible, but the patency rates obtained with this design are inferior to those obtained with conventional surgical bypass.