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Biomedical subjects

B Risberg

Publications and source records attributed to B Risberg.

At least 73 records · Page 4Linked to original sources
PubMed1998

Late aortic arch perforation by graft-anchoring stent: complication of endovascular thoracic aneurysm exclusion.

PURPOSE: To describe a fatal case of late aortic perforation by an endograft-anchoring stent. METHODS AND RESULTS: A 69-year-old woman presented 2 years after thoracoabdominal aneurysm repair with a 9-cm dilatation of the descending thoracic aorta proximal to the conventional aortic graft. A 38-mm Dacron graft with multiple Gianturco Z-stents sutured inside was placed transluminally across the aortic arch such that part of the uncovered portion of the proximal stent was partially across the left subclavian orifice. Four months later, the patient died from massive hemorrhage. Autopsy showed that the uncovered portion of the proximal stent had perforated the aortic arch. CONCLUSIONS: This case stresses the need for low-profile stent-grafts and smaller, more flexible introducer systems. Anchoring stents must be flexible, less traumatic, and strong enough to create a watertight seal even in tortuous vessels. To avoid aortic arch damage by thoracic stent-grafts, the proximal stent should be fully covered by the fabric.

Aged↗
PubMed1998

Antithrombin: facts and new hypotheses.

Antithrombin (AT) is an important inhibitor of the coagulation system, acting at many different levels of the coagulation cascade. This inhibitory action is enhanced several-fold by the glycosaminoglycan heparin. AT deficiency can be encountered in hereditary disorders, which are rare, or in acquired conditions, in which there is an excessive consumption of AT. Acquired AT deficiency is a common condition in sepsis, after major trauma or surgery, with or without associated disseminated intravascular coagulation (DIC). In these conditions, low levels of AT have been correlated with a poor outcome due to the development of multiple organ failure. Although supplementation with AT has been shown to attenuate the extent of organ failure in critically ill patients, it has not been possible to significantly improve the survival of these patients by administration of AT. An interesting new approach to AT treatment is based on the hypothesis that AT has specific effects that are independent of the coagulation cascade. Data from cell culture and animal experiments have demonstrated that AT can promote the endothelial production of prostacyclin and may therefore have anti-inflammatory actions. This effect is based on the interaction of AT with glycosaminoglycans in the cell membrane, and is independent of heparin. The role of AT in vessel wall antithrombogenicity is being increasingly appreciated. The concept of neointimal hyperplasia following vascular injury involves thrombin as an important mediator and thus, in addition to the anti-inflammatory effects of AT, new horizons in which AT may have an important role in the prevention of post-traumatic hyperplastic response are also evolving.

Animals↗
PubMed1997

The reciprocal translocation t(9;16)(q22;p13) is a primary chromosome abnormality in basal cell carcinomas.

The reciprocal translocation t(9;16)(q22;p13) was identified in three short-term cultured basal cell carcinomas (BCCs). The t(9;16) was the sole anomaly in one clone in two tumors and was accompanied by a second change that also affected the long arm of chromosome 9 in the third. In addition, other cytogenetically unrelated abnormal clones were also found in all three BCCs. The identification of t(9;16)(q22;p13) as a primary chromosomal abnormality in a subset of BCCs (we found it in 3 of 22 tumors) is especially intriguing against the background that the PTCH gene, which when mutated in the germ line presumably gives rise to the autosomal dominant basal cell nevus or Gorlin's syndrome, maps to chromosome band 9q22. None of the genes rearranged in the BCC-specific t(9;16)(q22;p13) translocation have been identified, but we hypothesize that the translocation represents the cytogenetic corollary of a tumorigenic recombination of PTCH with an as yet unknown gene in 16p13. If so, this would be the first time that a tumor suppressor gene causally involved in a hereditary cancer is shown to be frequently rearranged through a specific translocation in sporadic carcinomas of the same type.

Aged↗
PubMed1997

Bifurcated stent-graft for abdominal aortic aneurysm.

The purpose of this study was to examine bifurcated stent-graft implantation for abdominal aortic aneurysm. Fifty-seven patients were treated and followed with serial computed tomography scans for up to 3 years. Patients were allocated to three groups (first 20, second 20, last 17) according to when the repair was performed. Successful treatment is defined as exclusion of the aneurysm from the circulation, based on contrast computed tomography. Success rates in the three groups were 55%, 70% and 100%. Perigraft leak (endoleak) was present on initial assessment in 4/20, 2/20 and 1/17. Two of these aneurysms ruptured early in the postoperative period. Thereafter, leaks were sought and treated aggressively. Kinking and thrombosis occurred in six of the first 20 patients, but did not occur in any of the last 37 patients, in whom the graft limbs were routinely stent-supported throughout. Infrarenal implantation in very a short neck (< 10 mm), or a thrombus-lined neck was associated with proximal stent migration. In conclusion, changes in patient selection and technique have led to a steady rise in the short-term success rate of the stent-grafted implantation.

Aneurysm, Ruptured↗
PubMed1997

Canine model of abdominal aortic aneurysm treated by endovascular graft implantation.

The purpose of this study was to monitor the effects of endovascular graft implantation on a canine model of aortic aneurysm. Aneurysms were created in 10 dogs by fascial patch angioplasty of the infrarenal aorta. In five dogs, aneurysm creation was immediately followed by insertion of an endovascular graft. Central aortic and aneurysm sac pressures were then measured by needle puncture. The remaining five dogs were left untreated, as controls. Angiography was performed after aneurysm creation, after endovascular graft implantation, and at 1 month and 3 months. Following insertion of an endovascular graft, mean (s.d.) systolic pressure was lower in the aneurysm sac (82.9 (20.20) mmHg) than in the adjacent aorta (113.4 (25.9) mmHg; P < 0.002) in all the treatment group. The effects on diastolic pressure and mean pressure were less pronounced. Aneurysm size was increased in all controls (25.2 (9.55)%) and decreased in all of the treated group (22.5 (11.7)%; P < 0.001). In conclusion this model of aortic aneurysm has two important characteristics' it has multiple collateral branches, and it grows. Insertion of an endovascular graft was associated with a reduction in aneurysm sac pressure, reduced aneurysm growth, and fibrosis of the space between the aneurysm sac and the graft.

Animals↗
PubMed1997

A telescopic stent-graft for aortoiliac implantation.

OBJECTIVES: To test a new delivery system for a telescopic stent-graft. MATERIALS: Variable overlap between the components of this stent-graft combination allows length adjustment. This device differs from other multi-component stent-grafts in that both components are contained within a single delivery system. METHODS: The stent-graft was implanted in the distal thoracic to suprarenal aorta of five pigs (35-50 kg), where the arterial diameter falls by almost 50%. The proximal and distal components of the stent-graft were targeted to bony landmarks in the vertebral column. RESULTS: Inspection of completion angiograms showed both proximal and distal stent-grafts to be within 1 mm of their target locations in all five experiments. Overall combined stent-graft length varied from 13.5 cm to 16.1 cm depending on the location of the bony landmark chosen as the distal target, and on the size of the pig. CONCLUSIONS: This system may be useful for the repair of abdominal aortic aneurysm whenever preoperative sizing is difficult due to aortic tortuosity, or precluded due to the urgency of the procedure.

Animals↗
PubMed1997

Aneurysm pressure following endovascular exclusion.

OBJECTIVES: To assess the effect of stent-graft implantation on the pressure within an abdominal aortic aneurysm. METHODS: Aneurysm exclusion was performed using an aorto-uniiliac stent-graft in eight patients. Following stent-graft implantation, pressure measurements were performed through a catheter adjacent to the graft in the aneurysm. This "aneurysm pressure" was compared with radial arterial pressure. RESULTS: The pressure was lower in the aneurysm than in the radial artery, in all cases. Mean aneurysm pressure was 36.5/33.8 mmHg, while mean radial arterial pressure was 118.5/50.5 mmHg (p < 0.05, for both systolic and diastolic pressures). These findings corresponded with a reduction in the palpable abdominal pulse, and an absence of perigraft perfusion on follow-up computerised tomography. CONCLUSION: Stent-graft implantation produces a fall in the pressure within an abdominal aortic aneurysm.

Aortic Aneurysm, Abdominal↗
PubMed1997

The use of intravascular ultrasound as control procedure for the deployment of endovascular stented grafts.

OBJECTIVE: To assess whether intravascular ultrasound (IVUS), used systematically in a series of patients with abdominal aortic aneurysms (AAA), is a feasible control procedure to ensure correct transfemoral placement of endovascular stent grafts (TPEG). DESIGN: Descriptive study. MATERIALS AND METHODS: Fourteen patients with infrarenal aortic aneurysms were treated by the placement of one tube graft, 10 aorto-uni-iliac and three aorto-bi-iliac grafts. Arteriography and IVUS were performed before, during and after deployment of the graft to ensure correct placement in relation to side branches, and proper adaptation of the stents to the aortic wall. Postoperative CT-scan and arteriography served as control procedures. RESULTS: IVUS identified both renal arteries before graft deployment in eight of 13 (62%) patients. In the remaining patients only one renal artery was visualised due to interference from guidewires or the introducer system. Imaging during stent deployment was abandoned after IVUS catheter damage in two of three cases. Postprocedural IVUS was able to evaluate the expansion of the stents and the adaptation to the aortic wall in all instances. In four (29%) cases a leak was identified. Additional intervention included deployment of a further stent (n = 2) or redilation (n = 2). Covering of the renal arteries could only be indirectly determined by IVUS. CONCLUSION: IVUS can provide important decisive information before and after stented graft deployment, with the limitations that guidewires, introducer system and stents may cause interference. Contemporary IVUS designs are unsuitable for monitoring stent deployment.

Aged↗
PubMed1997

Renal arteries covered by aortic stents: clinical experience from endovascular grafting of aortic aneurysms.

OBJECTIVES: During the endovascular repair of abdominal aortic aneurysms (AAAs), effective anchoring of the stent-graft is difficult in the presence of a short infrarenal aneurysm neck. The aim of this study was to investigate renal artery patency and renal function after deployment of graft anchoring stents across the renal arteries. DESIGN: Retrospective open study. PATIENTS: Twenty-five renal arteries, in 18 patients treated by endovascular exclusion of an AAA, were intentionally covered with the Gianturco Z-stent to ensure stent graft attachment. METHODS: Renal artery patency was assessed by repeated spiral computed tomography (CT) scans and angiography. Creatinine levels, blood pressure and antihypertensive medication were recorded. Follow-up was a median 6 months (2-9). RESULTS: All 25 stent-covered renal arteries remained patent. CT showed a small infarct in one kidney. Creatinine was 108 mumol/l (89-133) before intervention and 98 mumol/l (87-127) at follow-up. Blood pressure was 150/80 mmHg on both occasions. Antihypertensive therapy was intensified in one patient whose creatinine level remained stable and whose separate renin sampling was normal. CONCLUSIONS: Covering the renal arteries with the Gianturco Z-stent does not seem to affect renal function within 6 months. Further follow-up is needed before suprarenal stent deployment can be advocated.

Aged↗
PubMed1997

Prognostic importance of the nuclear proteins p53 and Rb in conjunction with DNA, nuclear morphometry and grading in endometrial carcinoma.

In a series of 227 cases of endometrial carcinomas in FIGO stages I-IV, treated during the years 1984-89, immunohistochemical staining for the protein products of the two tumor suppressor genes p53 and retinoblastoma (Rb) were evaluated as prognostic factors with regard to tumor stage, FIGO grade, nuclear grade, morphometric nuclear parameters, DNA ploidy and S-phase fraction. Long-term survival analyses were endpoints and the Cox multivariate technique was used to evaluate the prognostic factors. In 20% of the cases p53 was positive. This was a genuine high-risk group associated with primary advanced carcinoma, nonendometrioid histology, poorly differentiated tumors, severe nuclear atypia, DNA aneuploidy, primary persistent tumors, recurrent tumors and a poor long-term survival rate (37% 5-year survival). In patients dying of their disease, 54% of the tumors stained positive for p53, compared with only 10% of the tumors not killing their hosts. Positive p53 staining was more common in older women. A pathologic Rb status (negative staining) was recorded in 6% of the cases. The Rb factor had only a minor influence on long-term survival and was not significant in multivariate analyses. The p53 staining status was the second most important prognostic factor after the nuclear grade in Cox multivariate analyses, after correcting for stage and age. Immunohistochemical staining for p53 protein should be included among previous available and important prognostic factors in endometrial carcinoma.

Journal Article↗
PubMed1997

Plasminogen activators and inhibitors in peritoneal tissue.

Serosal trauma elicits an inflammatory response which leads to the deposition of fibrin at injured sites, the residuals of which appear to be essential in excessive tissue repair and formation of intraabdominal adhesions. Local plasminogen activity may modulate this early phase of tissue repair. The present study was undertaken to investigate the distribution and cellular expression of plasminogen activators and their inhibitors in human peritoneal normal and inflamed tissue. Tissue-type plasminogen activator (t-PA) was expressed in subserosal capillary walls, and in normal mesothelium, but not in inflammation. Immunoreactivity for the plasminogen activator inhibitor type 1 (PAI-1) was present in normal mesothelium, and substantially increased in inflammation, where, in addition, immunoreactivity was found throughout the submesothelial tissue. This PAI-1 was partly co-localized with macrophages, as was the urokinase plasminogen activator (u-PA), suggesting an involvement of these cells in peritoneal tissue fibrinolysis. Inflammation or abrasion of the mesothelium during surgery is likely to cause a depletion of the local t-PA source and expose the potentially PAI-1-containing submesothelial tissue, thus promoting persistence of fibrin and formation of adhesions.

Epithelium↗
PubMed1997

European experience with a system for bifurcated stent-graft insertion.

PURPOSE: To test an endovascular aneurysm exclusion system in the presence of a wide range of challenging anatomic features. METHODS: Bifurcated endovascular stent-grafts were inserted in 52 patients and followed with serial computed tomography for up to 3 years. The device underwent several modifications during this time, the most significant of which represent the difference between the homemade (n = 42) and industry-made (n = 10) versions. RESULTS: The initial procedural success rate was 92% in the homemade group and 100% in the industry-made group. In the 3 years of follow-up, the long-term success rate was 64% in the homemade group and 90% in the industry-made group. The primary reasons for failure in the homemade group were graft thrombosis due to kinking early in the series and proximal stent migration later in our experience. All cases of migration occurred when the neck was < 15 mm in length, the neck was lined with thrombus, or the stent was implanted > 15 mm from the renal arteries. Kinking was subsequently overcome by implanting Wallstents throughout the graft limbs. The sole failure in the industry-made group was a case in which collateral perfusion reached the aneurysm through patent lumbar arteries. CONCLUSIONS: The fruits of this experience are a better technique, a better device, and, most importantly, a better understanding of the system's limits, as reflected in the current selection criteria.

Angiography↗
PubMed1997

Abdominal aortic aneurysms: experience with the Ivancev-Malmö endovascular system for aortomonoiliac stent-grafts.

PURPOSE: To describe a component-based aortomonoiliac stent-graft system and the first clinical results achieved with this device in endovascular abdominal aortic aneurysm (AAA) repair. METHODS: From November 1993 to October 1996, 45 patients aged 60 to 86 years underwent endoluminal exclusion of true AAAs (median diameter 60 mm) involving the common iliac arteries (median diameter 16 mm right and 15 mm left) using unilimb stent-grafts deployed with the Iancev-Malmö system. RESULTS: Six immediate conversions occurred in the beginning of the series due to endografts that were too short. Complications, including 2 inadvertent renal artery occlusions, 7 kinked grafts, 6 iliac artery dissections, and 3 perioccluder leaks, were prominent features in the first 15 patients. Five patients died in the postoperative period, four of whom were nonsurgical candidates. There were five significant stent-graft migrations: one 3 weeks after surgery due to mechanical injury of the proximal stent and four after 1 year owing to continuous dilation of a wide proximal neck, stent-graft placement in a conical, thrombus-lined proximal neck, and two instances of proximal extension separation from the main graft. Translumbar aneurysm perfusion required embolization in 3 patients. CONCLUSIONS: Despite early complications associated with a learning curve, exclusion of large AAAs using unilimb stent-grafts is feasible. Strict inclusion criteria are necessary in order to improve mortality among nonsurgical candidates and minimize the risk for late migration.

Aged↗
PubMed1997

Changing aneurysmal morphology after endovascular grafting: relation to leakage or persistent perfusion.

PURPOSE: To relate changing abdominal aortic aneurysm (AAA) morphology after endovascular grafting to the presence of leakage, collateral perfusion, and other factors. METHODS: Thirty-five patients who underwent successful AAA endovascular grafting were evaluated. Self-expanding Z-stents and Dacron grafts were applied in bifurcated and aortomonoiliac systems. Postoperative diameter changes were calculated from repeated spiral computed tomographic scans, angiograms, and ultrasonic phase-locked echo-tracking scans during a median 6-month follow-up (interquartile range [IQR] 3 to 12). RESULTS: At 12 months, the diameters of completely excluded aneurysms had decreased 6 mm (IQR 2 to 11; p = 0.006). The proximal graft-anchoring stents had dilated 2 mm (IQR 0.5 to 3.3; p = 0.01). The aortic diameters immediately below the renal arteries but above the stents had not changed. Endoleakage and collateral perfusion (n = 13) were each associated with preserved aneurysm size and a 12 times higher risk of aneurysm dilation. After the leakage or the collateral perfusion had been treated, the aneurysm size decreased. Aneurysms with extensive intraluminal thrombi presented a reduced risk of leakage or perfusion. CONCLUSIONS: The diameters of endovascularly excluded AAAs decrease, except in cases of leakage or perfusion. Careful follow-up of patients with aortic endografts is necessary.

Aged↗
PubMed1997

Release of creatine kinase, troponin-T, and tissue plasminogen activator in arterial and coronary venous blood during coronary artery bypass surgery.

Tissue plasminogen activator (t-PA) as a possible marker of endothelial injury during elective coronary artery bypass surgery was studied. T-PA antigen and activity were measured in arterial and coronary venous plasma in 14 patients, and compared to the markers of myocyte injury creatine kinase (CK-MB) and troponin-T (TnT). Cardiopulmonary bypass (CPB) lasted 86 (55-107) min, and aortic cross-clamping (cold, crystalloid cardioplegia) lasted 41 (25-62) min (median (central 90% percentile)). Blood flow in the great cardiac vein was measured by retrograde thermodilution, and increased from 49 (27-90) ml/min before CPB to a maximum of 92 (55-125) ml/min 40 min after declamping (not significant). CK-MB, TnT, and t-PA antigen and activity all increased during CPB, and were significantly higher in coronary sinus than arterial plasma after declamping the aorta. Net cardiac release ([coronary sinus-arterial concentration] x coronary flow) of TnT increased after the aorta was declamped, and was higher in the seven patients with the longest cross-clamping time than in the seven with the shortest time (p < 0.01). Cardiac release of CK-MB and t-PA antigen also increased after declamping, but with no significant difference between long and short cross-clamp times. t-PA activity, however, increased more in the patients with the longest cross-clamp times (p < 0.008). In conclusion, CK-MB, TnT and t-PA were released from the postcardioplegic heart. Release of t-PA indicates that postcardioplegic coronary endothelial activation or injury occurred t-PA activity as well as TnT increased more in patients with long times of cross-clamping, indicating that t-PA activity may be a possible marker of postcardioplegic endothelial injury or activation.

Aged↗
PubMed1997

Measurement of fibrinolytic components in human tissue.

The fibrinolytic system is involved in the resolution of thrombi and in tissue repair. Quantitation of the activators and inhibitors of this system at tissue level is crucial to further characterise these processes. Hitherto, there have been difficulties in measuring the individual components of the plasmin system in human vascular and peritoneal tissue. The aim of this study was to develop a protocol allowing quantitation of activators and inhibitors of plasmin generation at the tissue level. Following a strict protocol in the processing of tissue, the efficiency of extraction in tissue homogenisates was compared using buffers containing acetic acid, 1% Triton X-100 and thiocyanate. The influence of different modalities of normalisation was investigated by normalising to wet weight, total protein content, protein content in supernatant or DNA. Using the protocol, all buffers extracted components of the plasmin system sufficiently for detection. The acetic acid buffer yielded the greatest amount of protein, and in extracting plasminogen activators was comparable to the thiocyanate buffer and significantly more efficient than the Triton buffer (p < 0.05). The relationship between the individual components was unaltered by different means of normalisation. The protocol described, using an acetic acid buffer and normalising to wet weight, seems to be a simple and efficient technique for measuring components of the fibrinolytic system, at least in the tissues investigated.

Blood Vessels↗