Search PubMed⌕ Search

Biomedical subjects

James May

Publications and source records attributed to James May.

18 recordsLinked to original sources
PubMed2006

Durability of autogenous vein and polytetrafluoroethylene bypass grafts to the carotid arteries.

BACKGROUND: Bypass for extra-cranial arterial disease is infrequently carried out. We reviewed our experience to determine the outcome of carotid artery grafting using either an autogenous vein or polytetrafluoroethylene (PTFE). METHODS: Details of patients were recorded prospectively as part of a vascular surgical registry. Patients identified from the registry as having carotid artery bypass procedures were classified according to the type of conduit used. Comparison was made between patients with autogenous vein and PTFE grafts. RESULTS: Between 1978 and 2002, 24 patients (13 men and 11 women) mean age 60.0 +/- 13.4 years (range, 20-81 years) underwent 28 bypass procedures (three were bilateral and one was a reoperation). Symptomatic carotid disease was the clinical indication in 20 of 28 procedures (71.4%). Pathological indications included advanced atherosclerosis of the carotid arteries (15), past radiotherapy (4), failed stenting (3), resection of carotid body tumour (2), trauma (1), reoperation on a failed graft (1), carotid aneurysm (1) and iatrogenic carotid occlusion (1). An autogenous vein was used in 16, PTFE in 11 and autogenous artery in 1 of the patients. Using the Kaplan-Meier method, the overall patient cumulative 5-year survival was 84% and cumulative 5-year stroke-free survival was 93%. The combined perioperative stroke and mortality rate was 7.1%. Two patients had transient ischaemic attacks (7.1%), one had cranial nerve palsies (3.6%) and one required reoperation for bleeding (3.6%). Five-year cumulative graft primary patency using the Kaplan-Meier method was 74% for PTFE grafts and 92% for autogenous vein grafts (P = 0.37). CONCLUSION: Carotid artery bypass is a safe and a useful treatment option for complex extra-cranial arterial disease. Either PTFE or autogenous veins may be used as conduits.

Adult↗
PubMed2005

A prospective study of subclinical myocardial damage in endovascular versus open repair of infrarenal abdominal aortic aneurysms.

BACKGROUND: Endovascular repair of abdominal aortic aneurysms (AAAs) is considered to be less invasive and better tolerated by the cardiovascular system than open repair. Our aim was to assess the true incidence of perioperative myocardial damage associated with endovascular vs open infrarenal AAA repair. METHODS: Between July 1999 and June 2001, preoperative and postoperative serum troponin T (TnT) levels were measured in all patients presenting for elective AAA repair at Royal Prince Alfred Hospital. The incidence of myocardial damage was recorded on the basis of standard clinical, biochemical, and electrocardiographic changes or a subclinical increase of 50% or more in serum TnT. Patients were excluded if the TnT increase was associated with a significant increase of serum creatinine (> or =50%) with no other evidence of myocardial ischemia. The differences between the two groups were analyzed with the chi 2 test and odds ratios. RESULTS: A total of 35 open and 112 endovascular AAA repairs were included in the study. There was no significant difference in age, sex, preoperative serum creatinine, or preoperative serum TnT between the two treatment groups. Seventeen patients had biochemical evidence of myocardial damage, which was clinically obvious in only one patient. Even though the incidence of previous myocardial infarction was significantly higher in patients undergoing endovascular repair (41%) than open repair (22%; P < .05), the overall incidence of myocardial damage (clinical or subclinical) was significantly higher in the open group compared with the endovascular group (8 [25%] of 32 vs 9 [8%] of 109, respectively; odds ratio, 3.7; 95% confidence interval, 1.28-10.49; P < .02). CONCLUSIONS: There is a previously underestimated incidence of subclinical myocardial damage associated with surgery for infrarenal AAA which is lower after endovascular than open repair.

Aortic Aneurysm, Abdominal↗
PubMed2004

Rupture of abdominal aortic aneurysm: concurrent comparison of outcome of those occurring after endovascular repair versus those occurring without previous treatment in an 11-year single-center experience.

OBJECTIVE: The purpose of this single-center study was to compare findings at presentation and surgical outcome in patients in whom abdominal aortic aneurysms (AAAs) ruptured after endovascular repair and patients in whom AAAs ruptured before any treatment, over a defined period. METHODS: From May 1992 to September 2003, 1043 patients underwent elective repair of intact infrarenal AAAs. Endovascular repair was performed in 609 patients, and open repair in 434 patients. Eighteen of 609 patients (3%) who underwent endovascular AAA repair required treatment because of rupture of the aneurysm after a mean of 29 months (group 1). During the same 11-year period, another 91 patients without previous treatment required urgent repair of a ruptured AAA (group 2). Rupture was diagnosed at contrast material-enhanced computed tomography or by presence of extramural extravasation of blood at open repair. Except for a higher incidence of women in group 2, patients in both groups were similar with regard to demographics and clinical characteristics but differed in findings at presentation. Eight patients in group 1 had a known endoleak before AAA rupture, whereas contrast-enhanced computed tomography, performed in 15 patients at presentation, demonstrated an endoleak in all. Hypotension (systolic blood pressure <100 mm Hg) was noted at presentation in 4 of 18 patients (22%) in group 1 and 76 of 91 patients (84%) in group 2. All patients underwent open repair via a transperitoneal approach, except for 4 patients in group 1 and 3 patients in group 2 who underwent endovascular repair of ruptured AAAs. RESULTS: The proportion of patients with hypotension at presentation in group 1 (4 of 18) was significantly less than in group 2 (76 of 91; P < .01). The difference in perioperative (30 day) mortality rate in group 1 (3 of 18; 16.6%) compared with group 2 (49 of 91; 53.8%) was also significant (P < .01). The outcome in group 1 was therefore superior to that in group 2. CONCLUSIONS: This study confirms that endovascular AAA repair complicated by endoleak does not prevent rupture. The data suggest, however, that rupture, when it occurs in these circumstances, may not be accompanied by such major hemodynamic changes and high mortality as rupture of an untreated AAA. Further long-term follow-up and analysis in a larger group of patients are required to confirm the apparent intermediate level of protection afforded by failed endovascular repair, which does not prevent rupture but enhances survival after operation to treat rupture, possibly by ameliorating the hemodynamic changes associated with the rupture process.

Age Factors↗
PubMed2004

Symptomatic sac enlargement and rupture due to seroma after open abdominal aortic aneurysm repair with polytetrafluoroethylene graft: Implications for endovascular repair and endotension.

OBJECTIVE: We report 5 patients in whom a symptomatic perigraft seroma developed within the aortic sac, without vascular endoleak, after open repair of an abdominal aortic aneurysm (AAA) with a polytetrafluoroethylene (PTFE) graft. We also discuss possible relationships of this phenomenon to endovascular repair of AAAs. PATIENTS AND METHODS: Over 18 years, 1156 patients underwent repair of an AAA by one of the authors (B.M.B.). Of these, 1084 underwent open repair, 256 with PTFE grafts. Five patients in the PTFE group (2.3%) returned at a mean of 4.5 years with acute abdominal or back pain and enlargement of the aortic sac. Mean diameter of the aneurysms was 5.9 cm preoperatively and 8.1 cm at readmission. There was no evidence of vascular endoleak on computed tomography scans, but 1 patient had a retroperitoneal hematoma. RESULTS: Laparotomy in 4 patients disclosed a seroma containing firm rubbery gelatinous material under tension, histologically identified as amorphous eosinophilic material containing thrombus and degenerate blood cells in all cases. Rupture of the sac was confirmed in the patient with a retroperitoneal hematoma. The sac contents were evacuated and the integrity of the underlying grafts and anastomoses was confirmed before sac reduction, with imbricating sutures, and closure was performed. One patient died at 8 months of an unrelated cause; the other 3 patients remain well at mean follow-up of 12 months. The fifth patient received conservative treatment and remains asymptomatic 3 years after acute presentation. CONCLUSIONS: These findings of sac enlargement without vascular endoleak after open AAA repair are reminiscent of sac enlargement in the absence of endoleak after endovascular AAA repair. This has been referred to as endotension. The comparatively benign outcome in 5 patients with symptomatic sac enlargement, including 2 patients with rupture, after open AAA repair provides data to support a circumspect approach to endotension, especially in patients with asymptomatic disease, which has been reported as occurring in almost half of patients who received a PTFE Excluder endograft.

Aged↗
PubMed2004

Developing measures of surgeons' equipoise to assess the feasibility of randomized controlled trials in vascular surgery.

BACKGROUND: Equipoise is defined medically as a state of genuine uncertainty about the relative benefits of alternative treatment options. This study investigated individual and collective equipoise among vascular surgeons for controversial clinical questions to assess the feasibility of conducting randomized controlled trials. METHODS: Vascular surgeons throughout Australia and New Zealand received a survey by mail. RESULTS: Vascular surgeons (n=146, 77% response fraction) were able to quantify the strength of their treatment preferences and did so differentially between clinical scenarios using a simple scale. Almost one quarter (24%; 95% CI, 18%-32%) were completely undecided about whether carotid endarterectomy or carotid stenting was preferable to treat carotid stenosis in high-risk patients, indicating individual equipoise. In contrast, the vast majority of respondents (89%; 95% CI, 82%-93%) favored carotid endarterectomy over carotid stenting for average-risk patients, suggesting lack of community equipoise for this patient group. Similarly, there was lack of community equipoise for treatments for abdominal aortic aneurysm in high-risk patients with 88% (95% CI, 81%-92%) favoring a minimally invasive approach. Older respondents were consistently less willing to take part in randomized trials, with strength of treatment preference also independently predicting willingness to participate in 4 of 6 trials. CONCLUSIONS: Individual and community equipoise can be measured in a representative sample of surgeons as part of the feasibility assessment for future randomized controlled trials.

Adult↗
PubMed2003

Long-term outcome after aortic endovascular repair: the Sydney experience.

BACKGROUND: Since the inception of endovascular aortic aneurysm repair there has been concern about the unknown long-term outcome following this method of repair. AIM: The purpose of this study is to present the outcome of patients with abdominal aortic aneurysms (AAAs) who were treated by endovascular repair between 5 and 11 years ago. METHODS: Between May 1992 and November 1997, 190 patients (175 males 15 females, mean age 72 years) were treated at the Royal Prince Alfred Hospital. Overall, 1 of 3 patients were considered to have comorbidities that precluded open repair. Endoprostheses used were first generation in two thirds of patients and second generation in one third of patients. RESULTS: Eight patients (4.2%) died in the perioperative period. Endovascular repair failed in 20 patients (10.5%) who required conversion to open repair. Secondary conversion at a subsequent operation was necessary in 25 patients with rupture (n = 10), persistent endoleak (n = 11), endotension (n = 2), and inadvertent covering of the renal arteries by their prostheses (n = 2). Eight of the 20 patients presenting with rupture survived conversion to open repair. A long-term study of morphological changes in the proximal neck after endovascular AAA repair revealed a high probability (0.943 at 7 years) of no enlargement. Patients alive with successfully excluded AAA for 5-6, 6-7, 7-8, 8-9 year intervals of time, number 51, 36, 25, and 15, respectively. CONCLUSION: Considering that one third of patients were unfit for open repair and two thirds were treated with first generation prostheses, these results support the continued use of the endovascular method to treat AAA.

Aged↗
PubMed2003

Endoluminal repair of abdominal aortic aneurysm prevents enlargement of the proximal neck: a 9-year life-table and 5-year longitudinal study.

OBJECTIVE: Endoluminal repair of abdominal aortic aneurysm (AAA) is predicated on stability of the proximal neck of the aneurysm. Reports on morphologic changes in the proximal neck after endoluminal repair of AAA have thus far been limited in duration to 3 years or less. The aim of this study was to document changes in diameter of the proximal neck of AAA in a group of patients who had undergone endoluminal repair between 5 and 9 years previously. METHODS: Between May 1992 and December 1996, 61 patients with AAA were treated with endoluminal repair by the senior author. The following patients were excluded from the study group: those requiring primary conversion to open repair at the original operation (n = 8), those with false aneurysm (n = 1), and those with dissection in the proximal neck (n = 1). Fifty-one patients (48 men and three women) with a mean age of 71 years remained in the study group. The endoprostheses used were modified Parodi (n = 4), Endovascular Technologies (n = 14), White-Yu (n = 10), Stentor/Vanguard (n = 21), and Bard 1996 prototype (n = 2). Morphologic changes in the proximal aortic neck were studied with contrast computed tomographic scan with the methodology recommended by the Ad Hoc Committee for Standardized Reporting Practices for Endovascular AAA Repair (revised version). The maximum transverse diameter of the proximal neck was measured 1 cm below the most inferior renal artery. A Kaplan-Meier analysis was performed showing the proportion of patients at risk with a demonstrated enlargement of the neck at each interval of time compared with the predischarge computed tomographic scan. A longitudinal study of morphologic changes in the proximal aortic neck was also undertaken in 28 patients with successful endoluminal repair who survived 5 years. RESULTS: The Kaplan-Meier curve showed a probability of no dilatation of the proximal neck of 0.943 at 7 years after endoluminal AAA repair. Of 28 patients with 5 years of follow-up after discharge, only two had increases in the diameter of the proximal neck greater than 2 mm. The endograft in both patients had undergone migration before any proximal neck dilation. A paired t test showed that the overall average increase of 0.4 mm (standard error, 0.3 mm) in these 28 patients was not statistically significant (P =.23). CONCLUSION: A high probability (0.943 at 7 years) exists of no enlargement of the proximal neck of AAA after endoluminal repair. We hypothesize that endografts positioned correctly immediately below the renal arteries protect the proximal neck from dilatation in a manner that does not occur after open repair of AAA.

Aged↗
PubMed2002

An event-related functional MRI study comparing interference effects in the Simon and Stroop tasks.

The Stroop and Simon tasks typify a class of interference effects in which the introduction of task-irrelevant stimulus characteristics robustly slows reaction times. Behavioral studies have not succeeded in determining whether the neural basis for the resolution of these interference effects during successful task performance is similar or different across tasks. Event-related functional magnetic resonance imaging (fMRI) studies were obtained in 10 healthy young adults during performance of the Stroop and Simon tasks. Activation during the Stroop task replicated findings from two earlier fMRI studies. These activations were remarkably similar to those observed during the Simon task, and included anterior cingulate, supplementary motor, visual association, inferior temporal, inferior parietal, inferior frontal, and dorsolateral prefrontal cortices, as well as the caudate nuclei. The time courses of activation were also similar across tasks. Resolution of interference effects in the Simon and Stroop tasks engage similar brain regions, and with a similar time course. Therefore, despite the widely differing stimulus characteristics employed by these tasks, the neural systems that subserve successful task performance are likely to be similar as well.

Adult↗
PubMed2002

Australian audit for the endoluminal repair of abdominal aortic aneurysm: the first 12 months.

BACKGROUND: The Australian Safety and Efficacy Register for New Interventional Procedures - Surgical (ASERNIP-S) was contracted by the Commonwealth Department of Health and Aged Care to audit the procedure of endoluminal repair of abdominal aortic aneurysm. The purpose of the audit was to examine the safety and efficacy of the endoluminal graft (ELG) and, where possible, compare it to the open procedure. The first 12 months of data collection has now been completed. An overview of these results and some of the problems associated with the establishment of this audit are given. METHODS: The administrative infrastructure to support the audit is based at the ASERNIP-S office in Adelaide. To achieve high compliance rates, regular contact was maintained with surgeons. A reference group of senior vascular surgeons was established to provide expert support to the audit. RESULTS: By December 2000, ASERNIP-S had collected data on approximately 85% of privately performed ELG procedures during the first year of the audit. The early mortality rate was 1.3% in the endoluminal group compared to 2.6% in the open group. The rate of procedural complications was 15% in both groups, but the percentage of systemic complications was higher following the open repair. Aneurysm size and the number of pre-existing conditions had a statistically significant relationship to the variation in the number of complications for ELG patients. CONCLUSIONS: Good compliance has been obtained from vascular surgeons for submission of the operative data sets. ASERNIP-S aims to follow this group of patients closely to assess the medium to long-term durability of this procedure.

Aged↗
PubMedDate not supplied

A method for evaluating horizontal well pumping tests.

Predicting the future performance of horizontal wells under varying pumping conditions requires estimates of basic aquifer parameters, notably transmissivity and storativity. For vertical wells, there are well-established methods for estimating these parameters, typically based on either the recovery from induced head changes in a well or from the head response in observation wells to pumping in a test well. Comparable aquifer parameter estimation methods for horizontal wells have not been presented in the ground water literature. Formation parameter estimation methods based on measurements of pressure in horizontal wells have been presented in the petroleum industry literature, but these methods have limited applicability for ground water evaluation and are based on pressure measurements in only the horizontal well borehole, rather than in observation wells. This paper presents a simple and versatile method by which pumping test procedures developed for vertical wells can be applied to horizontal well pumping tests. The method presented here uses the principle of superposition to represent the horizontal well as a series of partially penetrating vertical wells. This concept is used to estimate a distance from an observation well at which a vertical well that has the same total pumping rate as the horizontal well will produce the same drawdown as the horizontal well. This equivalent distance may then be associated with an observation well for use in pumping test algorithms and type curves developed for vertical wells. The method is shown to produce good results for confined aquifers and unconfined aquifers in the absence of delayed yield response. For unconfined aquifers, the presence of delayed yield response increases the method error.

Forecasting↗