Anthony A. Nicholson

Mechanical properties of metallic stents: how do these properties influence the choice of stent for specific lesions?

AbstractPurpose: To assess selected balloon-expandable and self-expanding stents for radial force, flexibility, radio-opacity, and trackability, and to relate these physical characteristics to potential indications for placement.n Methods: Force-strain curves were plotted for each stent and the force required to produce 50% luminal narrowing was recorded. The ability of the stent to show elastic recoil following deformation was also noted. Flexibility was measured by bending the stents against a force transducer and recording the force required per degree of flexion. Radio-opacity was measured by comparing each stent against a standard aluminum step wedge. Trackability was measured by testing the ability of the stent on its delivery system to track over angles of 90° and 60°.n Results: The balloon-expandable stents showed greater radial strength and radio-opacity but, apart from the AVE Iliac Bridge stent, showed poorer flexibility and trackability. The self-expanding stents showed less radial force but were able to re-expand following deformity. They were generally more flexible and had better trackability but lower radio-opacity.n Conclusion: There is no stent which exhibits all the ideal properties required and therefore the interventionist will need to keep a range of stents available if all lesions are to be addressed.

The use of the wallstent endovascular prosthesis in the treatment of malignant obstruction of the superior vena cava

Seventeen patients (10 men and seven women) aged 48-76 years (mean 63.4) who were suffering from malignant superior vena caval obstruction had Wallstents implanted percutaneously to relieve the obstruction. Fifteen of the patients had previously been treated by radiotherapy or chemotherapy, with either failure to remit or later recurrence. Six patients required thrombolysis prior to stenting. All patients had rapid relief of the obstructive symptoms. This was sustained in 15 patients to date or at death. Two patients, both of whom had pre-stent lysis, developed stent thrombosis following withdrawal of anticoagulation at 4 months and 7 days respectively. Stenting has been shown to be extremely effective at relieving superior vena caval obstruction in these patients and is usually the only method available in this condition when other treatments fail. Whether all patients presenting with malignant superior vena caval obstruction should be stented de novo remains to be proven.

Anastomoses of the Ovarian and Uterine Arteries: A Potential Pitfall and Cause of Failure of Uterine Embolization

Four women with symptomatic uterine fibroids were treated by uterine artery embolization (UAE). In all cases both uterine arteries were embolized via a single femoral puncture with polyvinyl alcohol using a selective catheter technique. In three cases, the ovarian artery was not visible on the initial angiogram before embolization, but appeared after the second uterine artery had been treated. In one case of clinical failure following UAE, a repeat angiogram demonstrated filling of the fibroids from the ovarian artery. Anastomoses between uterine and ovarian arteries may cause problems for radiologists performing UAE and are a potential cause of treatment failure.

Treatment of chronic iliac artery occlusions by means of percutaneous endovascular stent placement

PURPOSEnA retrospective evaluation of outcomes in patients with chronic iliac occlusions treated with insertion of metallic endovascular stents, without previous thrombolysis, on an intention-to-treat basis.nnnMATERIALS AND METHODSnSeventy-two patients with chronic iliac occlusion underwent attempted stent placement from either the ipsilateral or contralateral femoral artery. There were 49 men and 23 women. Mean age was 63.1 years (range, 39-88 years). A total of 89 stents were deployed in 67 patients. Follow-up was from 24 to 69 months (mean, 37.5 months).nnnRESULTSnStents were successfully deployed in 67 patients (93%), with two early failures, giving a primary success rate of 90%. There were five significant and four insignificant procedural complications. There were four late failures (all within the first year) and four non-stent-related deaths.nnnCONCLUSIONnEndovascular stent placement offers an alternative to surgery in the treatment of chronic iliac occlusions.

Long-Term Follow-Up of Percutaneous Balloon Angioplasty in Adult Aortic Coarctation

AbstractPurpose: To assess long-term outcomes following percutaneous transluminal angioplasty (PTA) of congenital aortic coarctation in adults.n Methods: Seventeen patients underwent PTA for symptomatic adult coarctation of the aorta. Sixteen patients, with a mean age of 28 years (range 15–60 years), were reviewed at a mean interval after angioplasty of 7.3 years (range 1.5–11 years). Assessment included magnetic resonance imaging (MRI), Doppler echocardiography, and clinical examination. Current clinical measurements were compared with pre- and immediate post-angioplasty measurements.n Results: At follow-up 16 patients were alive and well. The patient not included in follow-up had undergone surgical repair and excision of the coarctation segment following PTA. Mean brachial systolic blood pressure for the group decreased from 174 mmHg before angioplasty to 130 mmHg at follow-up (p = 0.0001). The mean gradient had fallen significantly from 50.9 to 17.8 at follow-up (p = 0.001). The average number of antihypertensive drugs required per patient decreased from 0.56 to 0.31 (p = 0.234). No significant residual stenoses or restenoses were seen at MRI. Small but clinically insignificant residual pressure gradients were recorded in all patients using Doppler echocardiography. Complications included one transient ischemic attack at 5 days, one external iliac dissection requiring stent insertion, and a further patient who developed a false aneurysm close to the coarctation site at 12 months which subsequently required surgical excision.n Conclusion: PTA of adult coarctation is safe and effective in the long term. Although primary stenting has recently been advocated in the treatment of this condition, our results suggest that PTA remains the treatment of choice.

Vascular imaging and intervention in peripheral arteries in the diabetic patient

Diabetic patients are four times more likely to develop peripheral vascular disease than the general population. This disease is likely to be more aggressive, with five times more patients developing critical limb ischaemia. Early diagnosis and treatment allows up to 80% of these patients to have some form of surgical or endovascular re‐vascularisation. The primary imaging modalities to be used should be duplex ultrasound followed by angiography. Magnetic resonance angiography, however, holds out promise for the future as being a good method of non‐invasive imaging. Endovascular (interventional radiological) procedures have a major role to play in treatment of vascular stenoses and occlusions. Thrombolytic agents can be used to dissolve thrombus within occluded vessels and so restore patency. Percutaneous transluminal angioplasty is of value in dilating the stenotic lesions within the vessels and so restoring normal blood flow. Endovascular stents may be inserted to ensure longer term patency. There is indirect evidence to suggest that the outcomes of endovascular procedures in the diabetic patient are less good than those in the general population, but nevertheless such procedures may save the diabetic patient from primary amputation and allow healing of ischaemic ulcers. Copyright

Routine Follow-up by Magnetic Resonance Imaging Does Not Improve Detection of Resectable Local Recurrences From Colorectal Cancer

Objective:To determine if routine follow-up by magnetic resonance imaging (MRI) improves the detection of resectable local recurrences from colorectal cancer. Summary Background Data:Surgical treatment offers the best prospect of survival for patients with recurrent colorectal cancer. Unfortunately, most cases are often diagnosed at an unresectable stage when traditional follow-up methods are used. The impact of MRI surveillance on the early diagnosis of local recurrences has yet to be ascertained. Methods:Patients who underwent curative surgery for rectal and left-sided colon tumors were included in a program of pelvic surveillance by routine MRI, in addition to the standard follow-up protocol. Cases were then analyzed for mode of diagnosis, resectability, and overall survival. Results:Pelvic recurrence was found in 30 (13%) of the 226 patients studied. MRI detected 26 of 30 (87%) and missed 4 of 30 (13%) cases with local recurrence. Of the latter, 3 were anastomotic recurrences. In 28 (14%) patients, local recurrence was suspected by an initial MR scan but cleared by subsequent MRI or CT-guided biopsy. Recurrent pelvic cancer was diagnosed by MRI with 87% sensitivity and 86% specificity. In 19 (63%) cases, CEA was abnormally elevated, and 9 patients (30%) were symptomatic. Surgical resection was possible in only 6 patients (20%). There was no difference between MRI and conventional follow-up tests in their ability to detect cases suitable for surgery. Conclusions:Pelvic surveillance by MRI is not justified as part of the routine follow-up after a curative resection for colorectal cancer and should be reserved for selectively imaging patients with clinical, colonoscopic, and/or biochemical suspicion of recurrent disease.

Palliation of inoperable biliary obstruction with self-expanding metal endoprostheses: A review of 77 patients

Our experience of inserting 90 self-expanding metal endoprostheses in 77 patients with obstructive jaundice is described. All were inserted percutaneously. The longest metal endoprosthesis available was inserted where possible. For local economic reasons most patients had a normal serum albumin, and no evidence of metastases at presentation. Dilatation of biliary occlusions and strictures was not performed. Six re-interventions have been necessary because of tumour ingrowth or overgrowth. Serum bilirubin levels fell to normal in 98.7% of patients within 7 days of insertion. Self-expandable metal endoprostheses offer technical, psychological, physiological and anatomical advantages compared to other forms of palliation in biliary obstructions thought to be unsuitable for surgery. Furthermore, where stents have to be placed percutaneously because endoscopy is not possible, self-expanding metal endoprostheses should be used.

Accuracy of Carotid Duplex is Laboratory Specific and Must be Determined by Internal Audit

OBJECTIVEnTo assess the accuracy of carotid duplex in a single vascular laboratory at the prediction of an angiographic 70% internal carotid artery stenosis.nnnDESIGNnA retrospective review of all patients who underwent both carotid duplex and angiography in a 1-year period at a vascular unit which participates in the ACST trial.nnnMETHODSnPeak systolic velocity was used as a primary end-point in carotid duplex examinations with a PSV > 130 cm/s used as an indication for angiographic assessment. Biplanar arch aortography and selective carotid catheterisation were performed as indicated and diameter reduction calculated by the ECST method.nnnRESULTSnThe sensitivity of 130 cm/s for the detection of a 70% stenosis was 96% and the specificity 67%. If a PSV of 250 cm/s were used the sensitivity would be only 37% and specificity 96%.nnnCONCLUSIONSnApplying duplex criteria from one centre to another is inappropriate. Laboratory specific audit of duplex and angiography is essential before deciding to abandon preoperative angiography for carotid disease.

Treatment of rectal hemorrhage by coil embolization

Four patients, aged 54–84 years, presenting with life-threatening rectal bleeding from the superior hemorrhoidal artery, underwent percutaneous fibered platinum coil embolization via coaxial catheters. Preprocedure sigmoidoscopy had failed to identify the source of hemorrhage, because the rectum was filled with fresh blood. Embolization was technically and clinically successful in all four patients. Subsequent sigmoidoscopy confirmed the diagnoses in three patients as a solitary rectal ulcer, iatrogenic traumatic ulceration following manual evacuation, and a rectal Dieulafoy’s lesion. The other case was angiographically seen to be due to a rectal angiodysplasia. Embolization is an effective procedure in life-threatening superior hemorrhoidal arterial bleeding when endoscopic treatment fails, and should be preferred to rectosigmoid resection.