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Biomedical subjects

G H White

Publications and source records attributed to G H White.

At least 19 recordsLinked to original sources
PubMed2006

Endovascular popliteal aneurysm repair: are the results comparable to open surgery?

INTRODUCTION: The aim of this study was to review our experience of popliteal aneurysms using endovascular techniques. METHODS: Thirty popliteal aneurysms in 25 patients were treated over an 11-year period. Median aneurysm diameter was 26 (16-48) mm. Five were symptomatic and 25 asymptomatic. Patients were treated with the Haemobahn/Viabahn stent-graft (26), Passager (two), Aneurx (one), and PTFE homemade device (one). Data were assessed using life table analysis, and expressed as cumulative patency rates and standard error (SE). RESULTS: Median follow-up was 24 (range 1-95) months. Primary patency was 92.9% (SE 4.5%), 84.7% (SE 6.8%), 80% (SE 8.2%), 74.5% (SE 9.4%) and 74.5% (11.3%) at 1, 6, 12, 24 and 36 months, respectively. Cumulative secondary patency was 96.5% (SE 3.3%), 88.7% (SE 6.0%), 88.7% (SE 8.6%), 83.2% (SE 8.0%) and 83.2% (SE 9.8%) at 1, 6, 12, 24 and 36 months, respectively. CONCLUSION: Endovascular treatment of popliteal aneurysms in this series achieved patency rates similar to open surgery. Aneurysm repair was performed without peroperative deaths and the risks associated with open surgery.

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PubMed2005

Complications of aortic endografting.

Endovascular repair of abdominal aortic aneurysm has been shown to have a significantly lower perioperative mortality rate compared with open repair. It has been a blessing for patients at high risk who were previously denied treatment for their aortic aneurysms. It does, however, have a substantial need for re-intervention for complications. Many of these complications including endoleak, endotension, migration, post implant syndrome and conversion to open repair are unique to endovascular aneurysm repair. Others including injury to the iliac arteries, graft limb thromboses and structural failure of prostheses occur with greater frequency in endovascular repair compared with open repair. It is important, therefore, for vascular surgeons to be aware of these complications including their prevention and appropriate that patients are informed of their incidence. This review discusses the local and vascular complications of endovascular repair of abdominal aortic aneurysm with an emphasis on newer aspects.

Angioscopy↗
PubMed2003

Endovascular repair of abdominal aortic aneurysm in the multifocal atherosclerotic patient.

One of the major problems of treating aortic aneurysms has been the multifocal nature of atherosclerotic disease. Co-existing cardiovascular disease in the majority of patients together with chronic obstructive airways disease, renal impairment and hostile abdomen in some, has resulted in 1/3 of patients presenting with aortic aneurysms being regarded as high risk and unfit for open repair. Endovascular repair of aortic aneurysm therefore has much to recommend it since it avoids the need for laparatomy, cross clamping of the aorta and the obligatory blood loss associated with opening of the sac. Between May 1992 and March 2003 we have used the endovascular method to repair abdominal aortic aneurysms (AAA) in 583 patients. Successful repair was achieved in 563 patients (96%). The remaining 20 patients required primary conversion to open repair at the original operation. The 30-day perioperative mortality rate was 13 of 583 (2.2%). In this paper we summarise a number of studies that we have undertaken, comparing endovascular with alternative treatment methods and comparing various types of endovascular prostheses. In addition we report the long-term outcome of endovascular AAA repair as it relates to morphological changes in the proximal neck out to 9 years from operation. We conclude that despite the continuing small incidence of device failure, endovascular is the preferred method of AAA repair in the multifocal atherosclerotic patient. This view is based on the low perioperative mortality, superior survival compared with open repair and our experience of long-term stability in the proximal neck in the majority of patients.

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PubMed2003

Endotension. A review of current views on pathophysiology and treatment.

Most aneurysms shrink after successful endovascular repair. It has been observed, however, that some aneurysms continue to enlarge despite apparent exclusion of the sac by an endograft device. Unexplained abdominal aortic aneurysm (AAA) enlargement in these circumstances appears to be associated with high pressures inside the sac, and the phenomenon has been termed endotension. This paper reviews current theories and experimental evidence regarding the possible mechanisms of causation of endotension, and early experiences with treatment.

Animals↗
PubMed2001

Endoluminal repair of abdominal aortic aneurysms - state of the art.

This paper considers the historical aspects of endovascular aneursym repair; the major findings of our Departments experience over an 812-year period and reviews recent developments in endovascular prostheses. Analysis of 400 patients undergoing primary repair of abdominal aortic aneurysm between 1992 and 2000 revealed a perioperative mortality rate of 2.7% and primary conversion rate of 5%. With sequential studies it was shown that the outcome was better with bifurcated/aorto uni iliac grafts than tube grafts; better with second generation prostheses than first generation protheses and that survival in consecutive patients treated concurrently by open repair and endoluminal repair was superior in the endoluminal group. Endoluminal AAA repair is at a critical point of its development. It is unquestioned that it can dramatically reduce the need for intensive care and length of hospital stay and more recently it has been reported that survival is improved compared with open repair. The need for lifetime surveillance, the probability of graft failure and need for re-intervention, however, negate some of the advantages. The small incidence of unpredictable rupture following endoluminal AAA repair is a timely reminder of the need for continued careful follow-up.

Aortic Aneurysm, Abdominal↗
PubMed2001

Improved survival after endoluminal repair with second-generation prostheses compared with open repair in the treatment of abdominal aortic aneurysms: a 5-year concurrent comparison using life table method.

PURPOSE: The aim of this study was to compare the outcome of consecutive patients with abdominal aortic aneurysm (AAA) treated concurrently by means of open repair (OR) and endoluminal repair (ER) with second-generation prostheses by the same surgeons during a defined interval. METHODS: Between May 1995 and December 1998 second-generation (low profile, fully supported, modular) endoprostheses were implanted in 148 patients. These patients, together with 135 patients treated concurrently with OR during the same period, comprised the study group of 283 patients. Patient selection was based on aneurysm morphology. Those patients who were anatomically suitable for ER were treated with this method. The ER and OR groups were similar with regard to age, sex, and size of AAA. The ER group contained high-risk patients considered unfit for OR (n = 46), and the OR group contained high-risk patients who were anatomically unsuitable for ER (n = 19). Outcome criteria in both groups were survival and successful aneurysm repair. Success in the ER group was defined as exclusion of the aneurysm sac and stability or reduction in AAA maximum transverse diameter. Persistent endoleaks were classified as failures, regardless of whether they were subsequently corrected with secondary endovascular intervention. Data were analyzed with the life table method. The minimum period of follow-up for all patients was 18 months. RESULTS: The perioperative mortality rate was 5.9% in the OR group and 2.7% in the ER group (not significant). There was a statistically significant difference between the survival curves of the two groups in favor of the ER group when analyzed with the log-rank test (P =.004). The Kaplan-Meier curve for graft failure for the ER group revealed a 3-year graft success probability of 82%. Survival probability with successful repair in the OR group at 3 years was 85%. CONCLUSIONS: A concurrent comparison of ER with second-generation prostheses versus OR demonstrated a significant difference in survival in favor of the ER group. The probability of survival with successful repair at 3 years was similar in both groups.

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PubMed2000

Life-table analysis of primary and assisted success following endoluminal repair of abdominal aortic aneurysms: the role of supplementary endovascular intervention in improving outcome.

AIM: the aim of this study was to analyse the effect of supplementary endovascular intervention on the outcome of primary endoluminal repair of abdominal aortic aneurysm (AAA). METHODS: between May 1992 and December 1998, 266 patients underwent endoluminal repair of AAA. Minimum period of follow-up was 6 months. Those patients in whom the endoprosthesis could not be deployed were converted to open repair at the primary operation. Patients developing an early endoleak, within 31 days, were treated by a period of observation and secondary endovascular intervention in persistent cases. Patients developing a late endoleak were treated similarly, without a period of observation. Outcome was analysed by the life-table method. Primary success was defined as exclusion of the aneurysm from the circulation resulting from the original operation. Assisted success occurred when aneurysms with endoleaks became excluded from the circulation as a result of supplementary endovascular intervention. RESULTS: endoluminal repair failed in 17 patients requiring conversion to open repair at the original operation. Supplementary endovascular intervention was undertaken in 26 patients, with early endoleaks (n=6) and late endoleaks (n=20). Interventions involved deployment of secondary endoluminal grafts within the primary grafts (n=22), and coil embolisation (n=4). Successful exclusion of the aneurysm sac was achieved in 22 of 26 (85%) patients undergoing supplementary endovascular procedures. Conditional cumulative incidence of primary graft failure and secondary graft failure in the presence of all-cause mortality at 6 years was 47% and 25% respectively. CONCLUSIONS: supplementary endovascular intervention is an important adjunct to endoluminal AAA repair with the potential to improve outcome and avoid conversion to open repair. Successful supplementary endovascular intervention was achieved in 85% of patients in whom it was attempted. Life-table analysis showed these supplementary procedures to be durable in the long term.

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PubMed2000

Comparison of first- and second-generation prostheses for endoluminal repair of abdominal aortic aneurysms: a 6-year study with life table analysis.

PURPOSE: The outcome of endoluminal repair of abdominal aortic aneurysms with two generations of prostheses was analyzed and compared. METHODS: Between May 1992 and December 1998, 266 patients underwent elective endoluminal repair of an AAA. First-generation prostheses were used in 118 patients (group I), and second-generation prostheses were used in 148 patients (group II). The two groups were similar in age, sex, and size of AAA. The proportion of patients with comorbidities was higher in group I than in group II, but not significantly. First-generation devices were characterized by large (24F internal diameter) delivery systems, one-piece construction, and a lack of metallic support throughout their length. Second-generation devices had smaller (21F or smaller internal diameter) delivery systems, modular construction, and a metallic frame throughout the length of the prostheses. The major end-point criteria were survival and successful endoluminal repair. Success was defined as the exclusion of the aneurysm sac from the circulation, with stability or the reduction in AAA maximum transverse diameter. Persistent endoleaks were classified as failures, irrespective of whether they were subsequently corrected by means of secondary endovascular intervention. The minimum follow-up period was 5 months for each of the 266 patients. Analysis was performed by means of the life-table method. RESULTS: Perioperative mortality was not significantly different between group I (4.2%) and group II (2.7%). There was a statistically significant difference between the survival curves of the two generations, which favored group II (P =.012). There was a significant (P <.001) difference between the two generations of patients in their conditional probability of graft failure when the competing risk of all-cause mortality was considered. Second-generation patients were at a lower risk of graft failure than first-generation patients. The probability of failure, expressed as a proportion of grafts failing at 2 years, was 0.15 for patients with second-generation prostheses and 0.33 for patients with first-generation prostheses. CONCLUSION: Endoluminal AAA repair is a safe procedure, whether first- or second-generation prostheses are used. Survival and probability of graft success were significantly higher with second-generation prostheses than with first-generation prostheses. This improvement in outcome resulted from a combination of increasing clinical experience and advances in technology. A more accurate evaluation of the role of the endoluminal method in AAA repair would be achieved by studying patients in whom second-generation devices were used, rather than longer term studies in which first- and second-generation devices were used.

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PubMed1999

Devices for aortic aneurysm repair.

Although the technical success and short-term efficacy of endovascular grafts have now been demonstrated, the long-term durability of grafts used in the aorta remains to be proven. No long-term data are yet available regarding device durability or patient outcome beyond the initial few years. Recent evidence shows that the ability of endovascular grafts to cause shrinkage and regression of aortic aneurysms may have a paradoxic effect of distorting the endograft itself, thus causing geometric changes within the supporting metallic framework and, ultimately, device failure (Fig. 9). Thus, the desired positive effect of the device may, ironically, lead to its eventual failure.

Aortic Aneurysm↗
PubMed1999

Evaluation of disinfection and sterilization of reusable angioscopes with the duck hepatitis B model.

PURPOSE: Nosocomial transmission of viral hepatitis and retrovirus infection has been reported. The expected risk is greatest for the hepatitis B virus (HBV). The duck HBV (DHBV) has similar biologic and structural characteristics to HBV and has been adopted as a suitable model for disinfectant testing. METHODS: Angioscopic examination of the external jugular vein was performed on DHBV-infected ducks. After use, the instrument was air dried for 3 minutes. Samples were obtained by flushing the channel with 5 mL of phosphate buffered saline solution. The samples were collected immediately after drying (control), after flushing with 5 mL of water, after glutaraldehyde disinfection for 5, 10, and 20 minutes, and after ethylene oxide gas sterilization. Angioscopes were either precleaned or uncleaned before disinfection/sterilization. Residual infectivity was assessed with inoculation of samples into the peritoneal cavity of day-old ducks (n = 231). RESULTS: DNA analysis results of liver samples showed that all 38 control ducks became infected. The frequency of DHBV infection was reduced to 93% (14 of 15) by flushing the angioscope with 5 mL of sterile water. No transmission occurred after the use of any of the properly precleaned and disinfected/sterilized angioscopes. However, after the use of the uncleaned angioscopes, the transmission rate was 90% (9 of 10) and 70% (7 of 10) after 5 and 10 minutes of contact time, respectively, in 2% glutaraldehyde. Even after the recommended 20 minutes of contact time, there was still 6% (2 of 35) transmission. After ethylene oxide sterilization, two of the recipient ducklings (2 of 35) were infected with DHBV. CONCLUSION: There was no disease transmission after reuse of disposable angioscopes adequately cleaned before disinfection or sterilization. However, if the angioscopes are inadequately cleaned, DHBV can survive despite glutaraldehyde disinfection or ethylene oxide sterilization. This contrasts with previous in vitro and in vivo data with solid surgical instruments. It is postulated that the presence of a narrow lumen or residual protein shielding within the lumen may compromise effective inactivation of hepadnaviruses on angioscopes, with the potential risk for patient-to-patient transmission.

Angioscopes↗
PubMed1999

Adverse events after endoluminal repair of abdominal aortic aneurysms: a comparison during two successive periods of time.

PURPOSE: The aim of this study was to document the incidence rate of adverse events after endoluminal repair of abdominal aortic aneurysms (AAAs) during two successive periods of time. METHODS: One hundred ninety patients (175 men, 15 women; mean age, 72 years) underwent endoluminal repair of AAAs in a 5(1/2)-year period. Adverse events were documented prospectively for all the patients throughout this interval. An adverse event was defined as any of the following events: a death within 30 days, a conversion to open repair, the need for further intervention (either open or endovascular), the need for hemodialysis, a failure to cure the AAA, and wound complications. The patients were divided into two groups those who underwent operation in the initial 3-year period (group I; n = 75) and those who underwent operation in the subsequent 2(1/2)-year period (group II; n = 115). The results were analyzed for total adverse events for both periods of time and for difference in incidence rates within categories of adverse events between the two groups. RESULTS: Eight patients (4.2%) died in the perioperative period. The endoluminal repair failed in 17 patients (8.9%), which necessitated a primary conversion to open repair at the original operation. In 88 patients, 110 adverse events occurred. There was no significant difference in the incidence rates of adverse events in patients in group I (37/75) and group II (51/115). Apart from primary conversion (P =.007), there was no significant difference in the incidence rates of adverse events between group I and group II within the following categories: perioperative (within 30 days) deaths, primary conversion, secondary conversion, supplementary endoluminal repair, intervention for lower limb ischemia, hemodialysis necessitated, failure to cure the AAA as a result of persistent endoleak, and wound complications. CONCLUSION: Despite improvements in technology and increasing experience, adverse events continue to occur in a relatively high proportion of patients (45%) who undergo endoluminal repair of AAA. Reporting the incidence rates of adverse events provides a more accurate picture of the morbidity rates of the endoluminal method rather than simply listing the procedures as successes or failures. The similarity in the incidence rates of adverse events in patients in group I and group II suggests that there are inherent risks in the endoluminal method rather than iatrogenic complications that occur during the learning curve with a new technique.

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