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Biomedical subjects

T Whitbread

Publications and source records attributed to T Whitbread.

7 recordsLinked to original sources
PubMed1999

The effects of crossing porcine renal artery ostia with various endovascular stents.

OBJECTIVES: To compare the effects of crossing renal artery ostia with various stents. METHODS: The renal artery ostia of 24 large white pigs were covered with a Wallstent (nine ostia), a Palmaz stent (nine ostia) and a Memotherm stent (13 ostia). After an interval of 6-15 weeks, aortography, renal pressure and blood samples were performed and the pigs then sacrificed for histological examination. RESULTS: Histological examination revealed an organised collagen matrix with endothelial cells covering the struts in contact with the aorta. This occurred with all stents but was most organised with the Wallstent. This matrix did not involve the renal artery ostia crossed by Wallstents, but in one Palmaz stent and in 12/13 Memotherm stents, a disorganised acellular matrix caused partial ostial occlusion. There was no mean fall in renal artery pressure but traces were damped in 8/13 cases of partial occlusion. There was a rise in serum creatinine in two cases using the Palmaz stent. CONCLUSIONS: Covering renal arteries with the Wallstent appears to be safe in the short-term. Placement of stents with larger struts across renal arteries will require imaging methods, such as intravascular ultrasound (IVUS) to ensure that the ostia are not obstructed.

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PubMed1998

A combined approach to the treatment of proximal arterial occlusions of the upper limb with endovascular stents.

BACKGROUND: The traditional transfemoral approach to endovascular stenting is not ideal for proximal arterial lesions of the upper limb. The distance of the lesion from the femoral puncture site, flexibility and unsupported length of guide-wires/delivery systems and often acutely angled origins of the great vessels combine to make crossing the lesions and accurate deployment of the device difficult or impossible. Deployment of the stent via a brachial arteriotomy should obviate these problems. AIM: The authors report a series of patients with proximal arterial occlusions of the upper limb treated by endoluminal stenting using a combined surgical/radiological approach. PATIENTS AND METHODS: Using the combined approach we have attempted to treat 18 proximal upper limb occlusions (eight brachiocephalic origin, six subclavian origin, two subclavian artery and two axillary artery). Where possible, occlusions were treated by primary stent deployment. All patients received perioperative i.v. heparin followed by long-term aspirin. RESULTS: Revascularisation was successful in 15 of 18 proximal occlusions with complete resolution of symptoms. All stented vessels remain patent up to 36 months after the procedure and there have been no complications arising from the brachial arteriotomy sites. CONCLUSIONS: Primary stenting is the treatment of choice for proximal occlusions of the upper limb vessels. A combined surgical/radiological approach via a brachial arteriotomy can be used in these cases and is now the method of choice for the treatment of such lesions in this unit.

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PubMed1997

The effect of placing an aortic Wallstent across the renal artery origins in an animal model.

OBJECTIVES: To assess the effect on renal blood flow and renal function of placing a Wallstent (Schneider (Europe) AG) across the renal artery origins in an animal model. DESIGN: Laboratory animal study. MATERIALS AND METHODS: Six Large White pigs had Wallstents placed across the origins of one or both renal arteries. Preoperative jugular venous blood samples were submitted for blood count and urea and electrolyte estimation. The pigs were recovered for 6 weeks. At sacrifice the renal arteries and their origins were examined by aortography and direct pressure measurements were recorded from the renal arteries and both the stented and unstented portions of the aorta. Renal venous blood samples were submitted for blood count, urea and electrolyte and renin estimation while renal arterial blood samples were submitted to examination for red blood cell fragmentation. The aorta with contained stent, renal arteries and kidneys were submitted for histological examination. RESULTS: At sacrifice no renal arteries had occluded and the stent-covered origins appeared normal with no evidence of stenosis. This was confirmed histologically. There was no statistically significant difference between the arterial pressures measured in the stented and unstented portions of aorta and the renal arteries whether or not their origins had been covered by the stent. There was no statistically significant difference between the urea and electrolyte and renin levels of renal venous blood samples irrespective of whether or not the relevant kidney had a stent across its renal artery origin. Renal arterial blood samples showed no evidence of red blood cell fragmentation and histological examination of the kidneys showed no evidence of infarction or micro-emboli. Examination of the specimens by light and scanning electron microscopy demonstrated partial endothelialisation of the stents but the renal artery origins remained widely patent despite being crossed by at least one wire in all cases. CONCLUSIONS: It may be necessary to place stents across renal artery origins during endovascular repair of abdominal aortic aneurysms. It would appear that covering renal artery origins with a Wallstent has no effect on renal perfusion pressure or function in this short-term animal model.

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PubMed1996

A new animal model for abdominal aortic aneurysms:initial results using a multiple-wire stent.

OBJECTIVES: The effect of a plain 48-wire self-expanding flexible stent (Wallstent-Schneider (Europe) AG) on abdominal aortic aneurysms has been studied in a new animal model. METHODS: Aneurysms were created by interposing fusiform segments of glutaraldehyde-tanned bovine internal jugular vein into the infrarenal aortas of 12 Large White pigs. The first six pigs were assessed after 6 weeks by ultrasonography and arteriography; they were then sacrificed for pathological examination. Endovascular placement of the stents, 2 weeks after aneurysm creation, was performed under arteriographic control in the next six pigs. These pigs were assessed by ultrasonography and arteriography 6 weeks after stenting; they were then sacrificed for pathological examination. RESULTS: At 6 weeks the aneurysms in the first group were pulsatile with partial endothelialisation and no mural thrombus. Placement of the stent in the second group was accomplished easily. Stenting resulted in an immediate reduction in wall pulsatility of all aneurysms and thrombosis of the excluded aneurysm sac occurred in three cases. In the other three cases the pulse pressure in the sac was reduced. In all cases there was a significant reduction in maximum aneurysm diameter when measured 6 weeks after stenting. CONCLUSIONS: A pulsatile, non-thrombogenic aortic aneurysm model approaching human dimensions has been successfully developed for the study of endoprostheses prior to their clinical use. Endovascular placement of a plain, multiple-wire Wallstent was associated with reductions in aneurysm pulsatility, pulse pressure within the sac and maximum aneurysm diameter over the study period. Stenting was associated with thrombosis of the excluded aneurysm sac in 50% of cases.

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