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Biomedical subjects

S C Whitaker

Publications and source records attributed to S C Whitaker.

At least 19 recordsLinked to original sources
PubMed2003

True juxta-anastomotic aneurysms in the residual infra-renal abdominal aorta.

INTRODUCTION: abdominal aortic dilatation can occur above the graft following repair of infra-renal abdominal aortic aneurysm (AAA). This study aimed to determine the incidence and possible aetiological associations of recurrent juxta-anastomotic aneurysms following open repair of AAA. METHODS: the diameter of the infra-renal aorta above the graft of 135 patients who had previously undergone open AAA repair was determined using ultrasound. In those where the diameter was greater than 40 mm a CT scan was undertaken. Co-morbid and operative details were determined from the patients and their clinical notes. RESULTS: seven patients had true juxta-anastomotic aneurysms (>40 mm) in the residual infra-renal abdominal aorta, the occurrence of which was associated with tobacco smoking and hypertension. There was no association with other co-morbid factors, surgical operative details or the development of iliac aneurysms (which occurred in 3% of patients). CONCLUSIONS: true juxta-anastomotic aneurysms develop in the residual infra-renal neck of patients following open repair of abdominal aortic aneurysm. Tobacco smoking and hypertension are significant factors associated with the development of these aneurysms. This group of patients may warrant surveillance to prevent aneurysm rupture.

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PubMed2001

Imaging of abdominal aortic aneurysm before and after endoluminal stent-graft repair.

Imaging is an essential component of endoluminal aneurysm repair. Detailed imaging with computed tomography, magnetic resonance imaging and angiography, alone or in combination, is required for the initial assessment and planning. Careful, lifelong follow-up is essential since complications of endoluminal repair may take months or years to appear. Follow-up imaging requires a combination of plain film radiography, colour Doppler ultrasound and helical computed tomography. Magnetic resonance imaging may be valuable for the follow-up of non ferro-magnetic endografts and intra-arterial angiography will be required for specific cases.

Aortic Aneurysm, Abdominal↗
PubMed2001

Mortality and morbidity following endovascular repair of abdominal aortic aneurysms: analysis of two single centre experiences.

OBJECTIVE: to show how differences in anatomical and physiological risk factors can affect the outcome of endovascular repair of AAA by describing the experience of two centres with different selection policies. METHODS: one hundred and thirty-five patients (group I) were treated at Queen's Medical Centre (Nottingham, U.K.) using 101 in-house made and 34 manufactured stent-grafts. Median diameter, length and angulation of the proximal aneurysm neck were 26 mm, 27 mm, 40 degrees, respectively. Seventy-six patients had ischaemic heart disease, 47 had left ventricular failure, median forced expiratory volume in one second (FEV1) was 83%, median creatinine was 100 micromol/l and median age was 72 years. Fifty patients (group II) were treated at Timone Hospital (Marseilles, France) using seven in-house made and 43 manufactured stent-grafts. Median diameter, length and angulation of the proximal aneurysm neck were 25 mm, 34 mm, 33 degrees, respectively. Thirteen patients had ischaemic heart disease, two had left ventricular failure, median forced expiratory volume in one second was 101%, median creatinine was 108 micromol/l and mean age was 72 years. RESULTS: anatomical characteristics of the proximal neck were significantly worse in group I (p=0.02 for the three variables). Cardiac comorbidities were more frequent and mean FEV1 was lower in group I (p<0.0001 and p=0.001, respectively. Median aneurysm diameter was significantly greater in group I (65 mm) than in group II (53 mm) (p<0.001). Postoperative mortality was 9% and 0% in groups I and II respectively (p=0.03). The incidence of technical complications (groin wound complications and side branches endoleaks being excluded) was 20% and 0% in groups I and II, respectively (p=0.0006). CONCLUSION: postoperative mortality and technical complication rates were significantly greater in group I than in group II, readily explained by poorer general condition and worse anatomical characteristics of the proximal neck in group I.

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PubMed2001

Intrarenal color duplex examination of aortic endograft patients with suprarenal stents.

PURPOSE: To report an experience using intrarenal color duplex ultrasonography (ICDU) to detect high-grade renal artery stenosis in patients who had endovascular repair of abdominal aortic aneurysm (AAA) with suprarenal stent fixation. METHODS: Twenty-eight patients (25 men; mean age 71 years, range 58-83) who had endovascular AAA repair with suprarenal stenting at least 3 months prior to commencement of this study were screened with ICDU. Acceleration time (AT), peak systolic velocity (PSV), end diastolic velocity (EDV), and resistive index (RI) were measured. The Doppler waveform was quantitatively scored on a scale from 0 to 4. AT >0.07 seconds, RI <0.45, or a Doppler waveform score of 0 or 1 (indicating loss of early systolic peak) were indicative of high-grade renal artery stenosis. RESULTS: Median follow-up was 15.5 months (range 3-34). ICDU was successful in 54 (98%) of 55 kidneys scanned. No AT values exceeded 0.07 seconds, all RIs were >0.45, and no waveforms had loss of early systolic peak, indicating that no patient had evidence of high-grade renal artery stenosis. CONCLUSIONS: ICDU is a simple and affordable method that seems well suited to periodic screening in patients with suprarenal stents. Longer follow-up with a larger number of patients is needed before definite conclusions can be drawn about the effect of suprarenal stenting on renal circulation.

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PubMed2000

Anatomical risk factors for proximal perigraft endoleak and graft migration following endovascular repair of abdominal aortic aneurysms.

INTRODUCTION: proximal perigraft endoleak (PPE) and graft migration are associated with significant morbidity and mortality. Objective data establishing correlation between neck anatomy and these complications are lacking. The aim of this study was to analyse the anatomy of the neck in order to find which variables were significantly associated with PPE and graft migration. METHODS: one hundred and eighty-four patients underwent endovascular repair (EVR) of infrarenal AAA using an in-house custom-made stent graft (Gianturco stents plus Dacron). Thirty-one patients had PPE and fifteen had graft migration. Neck diameter was measured at the level of renal arteries and lower limit of the neck. Necks were classified according to shape. Neck angulation was measured from spiral computed tomography (CT) or magnetic resonance imaging (MRI) reconstructions, or angiograms. Thrombus or atheroma lining and presence of calcifications were recorded. RESULTS: neck angulation was significantly greater in patients who had PPE (50+/-16, p=0. 0005) or graft migration (54+/-20, p=0.003), compared to patients who had none of these two complications (37+/-18). Neck diameter was significantly greater in patients with PPE (p=0.05). Incidence of PPE or graft migration was not significantly higher in the presence of a conical shape, thrombus or atheroma lining and calcifications. CONCLUSION: neck angulation was the risk factor most significantly related to PPE and graft migration.

Anastomosis, Surgical↗
PubMed2000

Feasibility of using dynamic contrast-enhanced magnetic resonance angiography as the sole imaging modality prior to endovascular repair of abdominal aortic aneurysms.

OBJECTIVES: to establish the feasibility of using magnetic resonance imaging (MRI) with dynamic contrast-enhanced (DCE) MRA as the sole imaging modality in the assessment of patients prior to endovascular repair of abdominal aortic aneurysms (AAAs). DESIGN: DCE MRA with MRI and helical computed tomography (CT) examinations were performed in patients being assessed for suitability for an endovascular approach to repair of their AAA. Management outcomes determined by the two techniques were compared. MATERIALS: sixteen patients with AAA. METHODS: all subjects underwent DCE MRA/MRI and helical CTA. Criteria for suitability for endovascular repair were established. The management outcomes determined by the MRI findings were compared with those obtained by CTA. RESULTS: high-quality MRA/MRI and CT images were obtained in 16 patients. Six patients were considered suitable for an endovascular approach, one was considered borderline and nine were judged unsuitable. In all cases, the overall management determined by the two methods concurred. CONCLUSIONS: comparison of the two imaging modalities resulted in agreement as to suitability for an endovascular approach. We therefore conclude that in our group the use of MRI and DCE-MRA proved effective as a sole imaging modality for the assessment of these patients.

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PubMed2000

Incidence and treatment of intraoperative technical problems during endovascular repair of complex abdominal aortic aneurysms.

PURPOSE: The purpose of this study was to assess the incidence and management of intraoperative technical problems during endovascular repair (EVR) of complex abdominal aortic aneurysms (AAA). METHODS: From February 1995 to March 1999, 204 EVRs of nonruptured AAA were performed at our institution. One hundred seventy-six patients had an in-house custom-made graft; 172 were aorto-uni-iliac grafts, and four were aortoaortic grafts. Twenty- eight patients had a bifurcated graft. One hundred fourteen patients (56%) were high risk for conventional open repair. One hundred nine patients (53%) were not suitable for most commercially available devices. RESULTS: Intraoperative technical problems occurred in 81 patients (40%). There were 37 endoleaks (27 proximal, 10 distal), 15 graft stenoses, one failure of graft deployment, two graft thromboses, three aortoiliac ruptures, five renal artery occlusions (one bilateral, four unilateral), and 18 internal iliac occlusions (five bilateral, 13 unilateral). Endovascular management of these problems was successful in 37 of the 81 patients (46%) and included 15 balloon dilatations, 21 additional stent placements, and one graft thrombectomy. Fifteen of the 81 patients (19%) had open procedures (four periaortic ligature placements, six open aneurysm repairs, three common iliac ligations, and two extra-anatomic bypass grafts). In the remaining 29 patients, the on-table problem was managed expectantly. During follow-up, two of 37 patients (5%) who were treated successfully with endovascular procedures experienced recurrence. There were five deaths (33%) among the 15 patients who underwent open procedures. CONCLUSION: Intraoperative problems occur frequently during the endovascular management of complex aneurysms. Many of these problems can be managed with additional endovascular techniques without an increased risk of recurrence or procedure-related complications. Open procedures in high-risk patients carry a high mortality rate. The team performing EVR of AAA should be skillful in advanced endovascular and open surgical procedures.

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PubMed2000

Endovascular repair of perisplanchnic abdominal aortic aneurysm with visceral vessel transposition.

PURPOSE: To report a combined endoluminal and open surgical approach for a suprarenal abdominal aortic aneurysm (AAA) with coexistent splanchnic vessel stenoses. METHODS AND RESULTS: A 64-year-old man presented with an aneurysm of the proximal abdominal aorta and severe stenoses of the celiac axis and superior mesenteric artery (SMA). An initial 2-stage plan to stent the visceral vessel stenoses and exclude the aneurysm with a fenestrated stent-graft failed when the celiac lesion could not be crossed. The approach was changed to restore visceral perfusion with a bifurcated left iliosplenic and ilio-SMA bypass graft. Exclusion of the aneurysm was achieved with a custom-made suprarenal aortic tube stent-graft (Ivancev-Malmö) system. The patient is free of symptoms at 22 months, and there was no aneurysm visible on the 14-month CT scan. CONCLUSIONS: Hybrid techniques are an alternative treatment for complex perivisceral aortic aneurysms when total endovascular reconstruction is not possible.

Aortic Aneurysm, Abdominal↗
PubMed1999

A prospective study to assess changes in proximal aortic neck dimensions after endovascular repair of abdominal aortic aneurysms.

OBJECTIVE: The purpose of this study was to detect any change in the proximal neck diameter after endovascular repair of abdominal aortic aneurysm. METHODS: The study was performed in a teaching hospital with an endovascular program on 112 patients who had undergone endovascular repair of abdominal aortic aneurysm. The interventions were pre-endovascular and postendovascular repair of abdominal aortic aneurysms with contrast-enhanced, spiral computerized tomography, and the main outcome measures were change in aortic proximal neck diameter, change in maximum aortic diameter, presence of endoleaks, and change in length from lowest renal artery to aortic bifurcation. RESULTS: The median anterior-posterior and transverse diameter decreased from 63.5 mm before surgery to 50.4 and 54.5 mm, respectively, after surgery in a period of 4 years. This trend in reduction in maximum diameter was not seen in the patients with endoleaks. There was no significant change in the proximal neck diameters when measured at 5-mm intervals after endovascular repair. There was also no significant change in the aortic length after endovascular repair. CONCLUSION: We have not demonstrated any evidence for proximal neck dilatation after endovascular repair of abdominal aortic aneurysm.

Aorta↗
PubMed1999

Mortality rates following endovascular repair of abdominal aortic aneurysms.

PURPOSE: To present the perioperative and late mortality following endovascular repair (EVR) of abdominal aortic aneurysms (AAAs). METHODS: Data were collected prospectively on 221 patients undergoing AAA EVR over a 4-year period (median 5-month follow-up). Patients were classified preoperatively as high risk with at least 1 of these features: serum creatinine > 150 micromol/L, ischemic heart disease or poor left ventricular function, respiratory function < 50% of predicted normal, ruptured or symptomatic AAA, contraindication to or failed open repair, and age > 80 years. RESULTS: One hundred forty (63.3%) patients were classified as high risk, the most common criterion being cardiac disease (n = 96, 68.6%). There were 25 (11.3%) deaths in the 30-day perioperative period, 22 (15.7%) in the high-risk group compared to 3 (3.7%) in the acceptable-risk group (p = 0.02). The most common causes of perioperative death were multisystem organ failure and myocardial infarction. A further 21 (9.5%) late deaths occurred, 16 (11.4%) in the high-risk group and 5 (6.2%) in the acceptable-risk group (p > 0.1). CONCLUSIONS: The mortality of patients at acceptable risk undergoing EVR compares with the best published series for conventional open AAA repair. The perioperative and late mortality in the high-risk patients are substantially higher.

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PubMed1998

A study on the patency of the inferior mesenteric and lumbar arteries in the incidence of endoleak following endovascular repair of infra-renal aortic aneurysms.

OBJECTIVE: An endoleak is defined as the presence of contrast medium within the aneurysm sac on post-operative contrast-enhanced computed tomography scans (CT) in patients following endovascular repair (EVR) of abdominal aortic aneurysms (AAA). The aim of this study was to correlate the incidence of endoleaks with the presence of patent lumbar (LA) and inferior mesenteric arteries (IMA) as seen on pre-operative angiography. DESIGN, MATERIALS AND METHODS: Forty-seven patients were assessed pre-operatively by both CT and angiography by a blinded radiologist prior to EVR of AAA. The number and size of patent vessels was recorded and correlated with the incidence of LA or IMA endoleaks on follow-up CT. Patent lumbar vessels were scored: 1 = small, 2 = medium, 3 = large. RESULTS: Five patients were noted to have patent IMA on pre-operative angiography but none developed an endoleak. In this series, five patients had an endoleak due to a patent LA. The median score for patients with no endoleak was 1 (0-9) and for those with a lumbar endoleak 2 (0-5) (P = 0.26, Mann-Whitney U-test). The number of patent lumbar arteries was not predictive of a subsequent endoleak. Two out of nine (22 %) patients with large patent LA subsequently developed an endoleak. If a policy of pre-operative embolization on the basis of large patent LA had been adopted, seven patients would have had an unnecessary invasive procedure. CONCLUSION: Pre-operative angiography to look for patent LA and IMAs is not required in patients undergoing EVR or AAA.

Aortic Aneurysm, Abdominal↗
PubMed1998

Common iliac artery aneurysms in patients with abdominal aortic aneurysms.

OBJECTIVES: To determine the incidence of common iliac artery (CIA) aneurysms in patients with abdominal aortic aneurysms (AAA) and to evaluate the relationship between AAA and CIA diameter. METHODS: Spiral CT angiography was used to measure the maximum diameters of the abdominal aorta and the common iliac arteries of 215 patients with AAA. RESULTS: The median CIA diameter was 1.7 cm--significantly greater than the published mean of 1.25 (2 S.D. = 0.85-1.65) cm of an age-matched, non-vascular population. Thirty-four patients (16%) had unilateral and 26 patients (12%) bilateral CIA aneurysms > or = 2.4 cm diameter. Eight-six vessels (20%) were affected. Right CIA diameters were wider than left CIA diameters (p < 0.0001, Wilcoxon matched-pairs signed rank test). The correlation between AAA size and CIA diameter was weak. CONCLUSIONS: The AAA population has abnormally dilated common iliac arteries. In this population, common iliac artery aneurysms should be defined as those greater than 2.4 cm diameter. 20% of CIAs in patients with AAA are aneurysmal according to this definition.

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PubMed1998

Thrombus distribution and changes in aneurysm size following endovascular aortic aneurysm repair.

OBJECTIVES: To determine (a) changes in aneurysm size following endovascular repair, (b) the significance of collateral lumbar artery blood flow and (c) the relationship between thrombus distribution within the aneurysm sac and the development of a "lumbar endoleak". MATERIALS AND METHODS: 72 patients treated with endovascular stent-grafts were followed up with spiral computed tomography for a median of 11 (range 3-27) months. The cross-sectional area of the aneurysm was measured at the point of maximum diameter pre- and post-operatively. The distribution and quantity of thrombus was recorded pre-operatively and this was related to changes in aneurysm size and the development of lumbar endoleaks post-operatively. RESULTS: An increase in aneurysm size occurred in 22 patients, of whom 10 had endoleaks. Fifteen aneurysms did not change in size, including four with endoleak, and 35 aneurysms decreased in size with no endoleaks. There was a significant difference between the endoleak and no endoleak groups (Chi-squared test = 17.1 with 2 degrees of freedom (d.f.), p < 0.001). Nine endoleaks were from patent lumbar arteries. No patients with thick circumferential or posteriorly placed thrombus developed an endoleak arising from lumbar vessels (0/23 cases) compared to those with minimal or anteriorly placed thrombus (9/49 cases) (Chi-squared test with Yate's correction = 3.17 with 1 d.f., p < 0.1). CONCLUSIONS: Aneurysms do not decrease in size in the presence of a lumbar endoleak, and some expand significantly. A number of aneurysms increase in size despite no evidence of an endoleak on computed tomography (CT). Patterns of thrombus distribution may be able to predict patients at risk from persistent endoleak via lumbar vessels.

Aortic Aneurysm, Abdominal↗
PubMed1998

Spiral CT angiography versus aortography in the assessment of aortoiliac length in patients undergoing endovascular abdominal aortic aneurysm repair.

PURPOSE: To compare measurements of aortoiliac length obtained with spiral computed tomographic angiography (CTA) and aortography in patients undergoing endovascular aneurysm repair. METHODS: The distances from the lower-most renal artery to the aortic bifurcation and from the aortic bifurcation to the common iliac artery (CIA) bifurcation were measured using both CTA and aortography in 108 patients with abdominal aortic aneurysms. RESULTS: The level of agreement between CTA and aortography was high, with 69% of aortic and 76% of iliac measurements within 1 cm and > 90% within 2 cm of each other. Mean differences were -0.35 +/- 1.20 cm and 0.25 +/- 1.10 cm, respectively, for aortic and iliac lengths. Aortography overestimated renal artery to aortic bifurcation length in comparison to CTA (p = 0.003), particularly in patients with large aneurysms (> 6.5 cm) and lumen diameters > 4.5 cm (p < 0.0001). Measurements of CIA length were shorter by aortography than CTA (p = 0.02). CONCLUSIONS: There is a high level of agreement between CTA and aortography in the measurement of aortoiliac length, but aortography overestimates renal artery to aortic bifurcation length in patients with large-diameter aneurysms and wide aneurysm lumens. CTA is sufficiently accurate in the majority of cases to be used as the sole basis for the construction of endovascular grafts.

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PubMed1997

Early results of endovascular aortic aneurysm surgery with aortouniiliac graft, contralateral iliac occlusion, and femorofemoral bypass.

PURPOSE: The aim of this study was to evaluate the feasibility of endovascular aortic aneurysm repair with use of an aortouniiliac graft secured with self-expanding (Gianturco) stents. METHODS: Thirty patients with a median age of 72 years (age range, 52 to 86 years) and aneurysm diameter of 6.0 cm (range, 4.0 to 9.0 cm) were treated with an aortouniiliac endovascular graft. Of these 30 procedures, 28 were carried out electively and two as emergencies for leaking aneurysm. Of the 30 patients, 21 (70%) were considered to be at high risk for open surgery. A modified Gianturco stent, Dacron graft, and Wallstent were used for these procedures. RESULTS: Endovascular repair was successfully carried out in 25 of 30 (83.3%) patients. All these patients were mobile and had resumed a normal diet within 48 hours of the procedure. The overall 30-day mortality rate was two in 30 (6.6%), but it was one in 28 (3.5%) for the elective cases; all deaths occurred in the group at high risk for surgery. Other complications encountered within 30 days of procedure included myocardial infarction in one patient, pneumonia in two patients, homonymous quadrantanopia in one patient, and colonic ischemia in one patient, giving an overall morbidity rate of four in 30 (13.3%). At a median follow-up of 4 months (range, 1 to 13 months), 27 of 30 (90%) patients remain alive and well. CONCLUSION: Endovascular aortouniiliac repair of abdominal aortic aneurysm with Gianturco stent is feasible in both elective and emergency situations. It appears to be minimally traumatic, and the majority of patients deemed to be at high risk for open surgery can safely undergo endovascular repair. However, data on more patients with longer follow-up is required to determine its role in the management of abdominal aortic aneurysm.

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