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Biomedical subjects

A Nasim

Publications and source records attributed to A Nasim.

At least 37 records · Page 2Linked to original sources
PubMed1998

Changes in referral practice, workload, and operative mortality after establishment of an endovascular abdominal aortic aneurysm program.

PURPOSE: To determine the change in referral practice following establishment of an endovascular abdominal aortic aneurysm (AAA) program. METHODS: A prospective audit of all elective admissions for AAA was established in January 1994 at the initiation of an endovascular AAA program. A comparison was made between this cohort and the elective AAA repairs performed between 1981 and 1993. RESULTS: Since January 1994, 213 AAA patients (177 men; median age 73 years, range 54 to 88) have been referred for potential endovascular aneurysm repair. To date, 142 patients have undergone elective surgery (41 endovascular and 101 conventional). Between 1981 and 1993, 304 patients (255 men; median age 69 years, range 45 to 86) had elective aneurysm repair. Comparison of the two time periods has revealed significant increases in the number of tertiary referrals (41.8% versus 9.5%, p < 0.01), annual operations (50 versus 23, p < 0.05), and overall mortality (12% versus 6.7%, p < 0.05), the latter attended by a significant increase in cardiorespiratory comorbidity. CONCLUSIONS: The higher elective AAA mortality rate since the establishment of an endovascular program reflects a change in referral practice and may be directly attributable to an increase in the number of high-risk patients. An endovascular AAA program has clinical and financial implications for the hospital concerned.

Aged↗
PubMed1998

Arterial thrombosis: a complication of loop ileostomy.

Restorative proctocolectomy has become the surgical treatment of choice in ulcerative colitis. Most commonly, this is performed as a staged procedure which includes formation of a defunctioning loop ileostomy. High output loop ileostomies are associated with both local and systemic complications. We describe two patients with loop ileostomies who developed acute arterial thrombosis, a complication not previously described, thus further emphasizing the importance of careful management and early reversal of high output ileostomies.

Aged↗
PubMed1997

Microembolization during endovascular and conventional aneurysm repair.

PURPOSE: Endovascular aneurysm repair has been advocated as a "minimally invasive" alternative to conventional aneurysm surgery. However, because of manipulation within the aneurysm sac, endovascular techniques may result in massive microembolization. METHODS: In this study lower limb microemboli were quantified in 29 patients undergoing conventional (11 straight and 7 bifurcated grafts) and endovascular aneurysm repair (8 aortoiliac, 1 straight, and 2 bifurcated grafts) by insonation of the superficial femoral artery with a 2 MHz Doppler probe. Emboli were detected as high-intensity, short-duration signals on the background Doppler trace. Differentiation of gaseous emboli from particulate emboli was achieved by calculation of the sample volume length (emboli velocity x duration = sample volume length) for each embolus (N = 4927). Previous experiments had determined that a sample volume length < 1.4 cm represented particulate embolization. RESULTS: The number of gaseous, particulate, and total emboli were significantly greater in the endovascular group compared with the conventional group (p < 0.05). CONCLUSIONS: These data demonstrate that peripheral microembolization is significantly higher during endovascular aneurysm repair than during conventional surgery. Methods to reduce embolization must be developed before endovascular aortic surgery is widely adopted.

Aged↗
PubMed1997

Surgical management of 671 abdominal aortic aneurysms: a 13 year review from a single centre.

OBJECTIVE: To audit the results for abdominal aortic aneurysm (AAA) repair from a single centre over a 13 year period. DESIGN: Retrospective survey. SETTING: Vascular unit of a major teaching hospital. MATERIALS: Six hundred and seventy-one consecutive patients divided into two groups: group A (1981-87) and group B (1988-93). CHIEF OUTCOME MEASURES: Mortality rates, cause of death and major complications in patients undergoing elective, urgent and ruptured AAAs. RESULTS: Elective repair was performed in 313 (47%) patients, urgent repair in 80 (12%) and emergency repair for rupture in 278 (41%). A vascular surgeon performed the procedure in 94% of patients. The overall mortality was 21 patients in the elective group (6.7%), 13 in the urgent group (16%) and 148 in the ruptured group (53%). Mortality rates have not fallen during the study period but more patients in group B had ischaemic heart disease. Sixty patients (9%) required further operative procedures on 66 occasions: 24 elective cases (8%), 8 urgent cases (10%) and 28 ruptured cases (10%). There were 23 deaths in these 60 patients (38%) who underwent re-operation (5 elective, 2 urgent and 16 ruptured). Major postoperative complications included cardiac events in 212 (32%) patients, respiratory failure in 202 (30%) and renal failure in 90 (13%). Major causes of death included cardiac disease in 67 patients (37%), cardiac disease with coagulopathy in 22 (12%) and cardiac disease with respiratory failure in 16 (9%). Logistic regression analysis showed that in the elective group, cardiac or renal failure were significantly associated with death; and in the ruptured group cardiac, respiratory or renal failure were significantly associated with death. CONCLUSIONS: More high risk patients with ischaemic heart disease are undergoing AAA repair. Postoperative cardiac, respiratory or renal failure are significant causes of death in AAA patients.

Aged↗
PubMed1997

Ultrasound-based quantification of emboli during conventional and endovascular aneurysm repair.

PURPOSE: To differentiate and quantify the type and number of lower limb emboli occurring during endovascular aneurysm repair, as compared to conventional surgery. METHODS: Thirty-eight patients underwent elective infrarenal aneurysm repair using a conventional surgical approach in 18 and an endovascular procedure in 20. Emboli were detected using a Doppler ultrasound system with a 2-MHz transducer interrogating the mid superficial femoral artery. Lower limb emboli were differentiated as particulate or gaseous based on the physical distance traversed by the embolic signal. RESULTS: Significantly more particulate (median 108 versus 59, p = 0.015) and gaseous (134 versus 46, p = 0.008) emboli were detected during endovascular aneurysm repair as compared to conventional surgery. Clinically, no case of massive microembolization occurred in either group, but one patient in the conventional group required a femoral embolectomy, and three patients undergoing endovascular repair developed self-limiting trash feet postoperatively. In patients undergoing endovascular aortomonoiliac aneurysm repair, there was only a poor correlation between the number of particulate emboli and either procedural duration or operator experience. CONCLUSIONS: The apparent lack of a relationship between particulate embolization and operative time or technical experience suggests that manipulation of endoluminal devices within the aneurysm sac may not be the sole determinant of intraprocedural embolization. Other as yet undetermined factors may predict patients at high risk for massive embolization.

Aged↗
PubMed1997

Aortomonoiliac endovascular grafting: difficult solutions to difficult aneurysms.

PURPOSE: To describe a refined technique for aortomonoiliac endograft exclusion of abdominal aortic aneurysms (AAAs). METHODS: A tapered aortomonoiliac graft was prepared from an 8-mm thin-walled expanded polytetrafluoroethylene tube graft predilated proximally to 35 mm and tapered distally to 15 mm. The proximal graft was sutured to a 5-cm-long, predilated Palmaz stent, which was mounted on a 30-mm balloon and backloaded into a 21F packaging sheath. With the patient under general anesthesia and both common femoral arteries exposed, the endograft was anchored in the infrarenal aorta and subsequently passed into one iliac system, where it was anastomosed to the iliac or femoral vessels. The contralateral common iliac artery was occluded, and an extra-anatomic, femorofemoral, or iliofemoral bypass grafting was performed. RESULTS: Twenty of the 25 AAAs treated to date with this technique have been successful, with aneurysm exclusion achieved in 18 (2 minor distal endoleaks are scheduled for endovascular repair). The technical failures were analyzed, resulting in enhancements to the technique. Complications included 2 early (< 30 days) deaths, 1 case of minor embolization, 1 transient renal failure, 1 pulmonary embolus, and 1 wound infection. The only late complication was a graft infection localized to the groin. CONCLUSIONS: Aortomonoiliac endovascular aneurysm repair is effective in patients with AAAs involving the iliac arteries. Short-term results are acceptable, but long-term efficacy must be addressed before this procedure is widely adopted. Technical changes made in response to early learning curve problems have led to a safer, more reliable procedure.

Aged↗
PubMed1997

Surgical decompression of thoracic outlet syndrome; is it a worthwhile procedure?

During a 20-year period from 1974 to 1994, 37 thoracic outlet decompressions were performed. There were 28 females and six males (ratio 5:1). The median age was 37 years (range 15-64). Symptoms were predominantly neurological in 29 limbs (78%), arterial in five limbs (14%) and venous in three limbs (8%). Limb pain and paraesthesia were the most common symptoms. Surgical decompression was performed via a supraclavicular approach in 24 limbs (65%) and a transaxillary approach in 13 limbs (35%). A cervical rib was excised in 21 limbs (57%), a first rib in 10 limbs (27%), a cervical and first rib in one limb (3%) and a cervical band in five limbs (13%). Arterial reconstruction was only required in three limbs (8%). There were a total of four complications (11%). The outcome of surgical decompression was assessed by using a questionnaire completed by the patient. Overall 27 patients (87%) felt that the operation was worthwhile. These results show that surgical decompression for thoracic outlet syndrome is a worthwhile procedure and is associated with relatively few complications.

Adolescent↗
PubMed1996

Endovascular repair of abdominal aortic aneurysm: an initial experience.

Endovascular repair of abdominal aortic aneurysm (AAA) was attempted in ten patients over a 12-month period. Median age was 72 (range 61-82) years and median AAA diameter was 5.5 (range 5.2-6.0) cm. An aortoaortic (tube) graft was used in seven patients and a tapered aortoiliac reconstruction in three. There were two failures requiring conversion to open repair. Additional procedures included iliac artery angioplasty (two), coil embolization of an associated common iliac aneurysm (one) and femorodistal bypass (one). Median operating time was 162 (range 95-270) min and median blood loss was 1200 (range 800-2000) ml. Median hospital stay was 9 (range 5-21) days. Complications included death (one), reversible acute tubular necrosis (one) and prolonged ventilation (one). Postoperative evaluation with duplex ultrasonography and computed tomography demonstrated three perigraft leaks (two proximal and one distal). It is concluded that endovascular repair of AAA is feasible but is associated with significant complications and requires careful evaluation before widespread use.

Aged↗
PubMed1996

Elastase-induced matrix degradation in arterial organ cultures: an in vitro model of aneurysmal disease.

PURPOSE: Abdominal aortic aneurysms are characterized by degradation of the extracellular matrix, induction of endogenous metalloproteinases (MMPs), and development of a chronic inflammatory infiltrate. Despite intensive analysis of end-stage tissue, aneurysm pathogenesis remains obscure. The aim of this study was to develop an in vitro model of aneurysmal disease. METHODS: Porcine aortic organ cultures were preincubated with pancreatic elastase before culture in standard conditions for up to 14 days. The extent of matrix degradation at various time points was determined by quantitative histologic estimation of collagen and elastin concentration. Endogenous metalloproteinase production within the tissue was quantified by gel enzymography and immunoblotting. A separate series of experiments was performed to investigate the effect of incorporating autologous leukocytes into the culture system. RESULTS: Although exogenous elastase was removed after 24 hours, substantial degradation of the aortic extracellular matrix occurred in the subsequent 13 days in tissue culture. Analysis of samples preincubated with elastase (100 U/ml) for 24 hours before tissue culture demonstrated that elastin degradation occurred in a time-dependent manner (p < 0.001) and was not confined to the initial phase of exogenous elastase activity. Gelatin gel enzymography revealed a time-related production of metalloproteinases (55 to 250 kDa) within the aortic tissue. The presence of MMPs-1, 2, 3, and 9 was determined by immunoblotting. Immunohistochemistry identified the vascular smooth-muscle cell as the source of MMPs-1, 2, and 3. Addition of autogenous leukocytes to elastase-pretreated tissue initiated an inflammatory infiltrate within the aortic wall, which further enhanced both matrix degradation and MMP production (p < 0.001). CONCLUSIONS: These data demonstrate that aortic samples pretreated with elastase before tissue culture undergo matrix degradation with MMP production and the development of an inflammatory infiltrate. These changes mirror the pathophysiological events within established aneurysms. It is suggested that this model may be useful in understanding early pathogenic events within aneurysmal tissue.

Animals↗
PubMed1996

Angiogenesis in abdominal aortic aneurysms.

OBJECTIVES: To determine the degree of neovascularisation in the wall of abdominal aortic aneurysms in comparison to atherosclerotic control aortas, and to correlate the angiogenic response with the extent of the cellular inflammatory infiltrate. DESIGN: Histopathological study. MATERIALS: Aortic samples were obtained from patients with abdominal aortic aneurysms and from atherosclerotic controls. METHODS: Samples were stained with haematoxylin and eosin, and Miller's elastin and Van Gieson stain, EVG, and a monoclonal antibody specific to human endothelial cells. Within the aortic wall three histological regions were defined, the media, the adventitia and a transition zone. The number of capillary like, thin walled vessels were measured in each region, and the cellular infiltrate was quantified. RESULTS: The number of newly formed vessels was increased in all layers of aneurysmal wall in comparison to control samples (p<0.001). The degree of neovascularisation correlated with the extent of the inflammatory infiltrate (rs=0.45, p<0.01). CONCLUSIONS: This study demonstrated that abdominal aortic aneurysms are associated with a marked angiogenic response, which is related to the degree of inflammation within the aortic wall. It is hypothesised that anti-angiogenic agents may play a role in the medical management of aortic aneurysmal disease.

Aged↗
PubMed1996

Oxygen free radical and cytokine generation during endovascular and conventional aneurysm repair.

OBJECTIVES: Endovascular aneurysm repair has been proposed as a "minimally invasive" alternative to conventional aneurysm resection. One of the most important potential benefits of endoluminal surgery is the avoidance of aortic cross clamping, which may attenuate the ischaemia-reperfusion injury that complicates open aneurysm repair. This study aimed to quantify the metabolic response to both conventional and endovascular aortic surgery. DESIGN: Prospective clinical study. SETTING: University hospital. METHODS: Femoral vein blood samples (pre-clamp, during aneurysm repair and 5 and 30 min post reperfusion) were obtained from 12 patients undergoing aortoaortic aneurysm repair, six by conventional transperitoneal inlay replacement (median age 71 years, median aneurysm diameter 5.8 cm), and six by endoluminal deployment of a straight endograft (median age 73 years, median aneurysm diameter 5.5 cm). All endovascular procedures were completed satisfactorily with no conversions to conventional surgery. OUTCOME MEASURES: Venous blood samples were analysed for oxygen free radical (OFR) production using the quantifiable oxidation of IgG in plasma, and cytokine (IL-1 beta and TNF-alpha) generation by radioimmunoassay. [table: see text] RESULTS: The results are given as median values with interquartile ranges: CONCLUSIONS: These results suggest that the ischaemia-reperfusion response associated with conventional aneurysm surgery may be largely negated by endovascular techniques. This may have significant consequences as the generation of oxygen free radicals and cytokines have been implicated in the development of systemic organ failure following aortic surgery.

Aged↗
PubMed1996

Proximal stent deployment without contrast during endovascular aneurysm repair: an improved technique.

PURPOSE: To describe a technique to enhance stent visibility on the fluoroscopic monitor during aortic endograft deployment. TECHNIQUE: To assist in accurate positioning and deployment of the proximal stent in a Parodi-type aortic endograft, the stent is affixed to the balloon so that the radiopaque marker sits at the stent's distal end. When the device is in position and the sheath is retracted, the stent and the radiopaque balloon markers are clearly seen on the fluoroscopic image. Using normal saline only to inflate the balloon allows the stent to remain visible throughout deployment. CONCLUSIONS: The use of saline rather than contrast medium for balloon inflation provides continuous visualization of the stent during expansion, thus facilitating accurate deployment and early recognition of balloon migration within the stent.

Angioplasty, Balloon↗
PubMed1995

Cloning and characterisation of the Schizosaccharomyces pombe rad32 gene: a gene required for repair of double strand breaks and recombination.

A new Schizosaccharomyces pombe mutant (rad32) which is sensitive to gamma and UV irradiation is described. Pulsed field gel electrophoresis of DNA from irradiated cells indicates that the rad32 mutant, in comparison to wild type cells, has decreased ability to repair DNA double strand breaks. The mutant also undergoes decreased meiotic recombination and displays reduced stability of minichromosomes. The rad32 gene has been cloned by complementation of the UV sensitive phenotype. The gene, which is not essential for cell viability and is expressed at a moderate level in mitotically dividing cells, has significant homology to the meiotic recombination gene MRE11 of Saccharomyces cerevisiae. Epistasis analysis indicates that rad32 functions in a pathway which includes the rhp51 gene (the S.pombe homologue to S.cerevisiae RAD51) and that cells deleted for the rad32 gene in conjunction with either the rad3 deletion (a G2 checkpoint mutation) or the rad2 deletion (a chromosome stability and potential nucleotide excision repair mutation) are not viable.

Amino Acid Sequence↗