[Midterm results after endovascular aortic aneurysm repair in the elderly]. / Endovaskuläre Aneurysmachirurgie beim alten Menschen--Methode der ersten Wahl?

During the past decade, endovascular aneurysm stent graft repair (EVAR) of abdominal aortic aneurysms has emerged as a less invasive and less burdening alternative to open surgical repair. We hypothesize that EVAR may become the treatment method of choice among elderly patients. During a 7-year-period, EVAR was performed in 654 patients at our institution. One hundred fifty seven (20 %) of these patients were older than 75 years. Our prospectively acquired database was reviewed with respect to midterm results of this elderly population. Aneurysm-related events (aneurysm-related death, endoleaks, conversion, renal infarction or aneurysm rupture) and secondary interventions were the main study endpoints. There were significantly (p < 0.05) higher endoleackage-, conversion and renal infarction rates among this subgroup of patients. In addition, aneurysm related morbidity and mortality were significantly elevated (p = 0.0011). The discussion about early operation at younger age and smaller aneurysm diameter continues. Nevertheless, improved EVAR devices and surgeon experience may make improve future results. Elective endovascular repair failed to demonstrate any benefit in elderly patients (> 75 yrs.) in the midterm outcome. In rupture, this procedure might be the treatment method of choice for patients in this age group who meet specific anatomical criteria.

STEP--a System for Teaching Experimental Psychology using E-Prime.

Students in psychology need to learn to design and analyze their own experiments. However, software that allows students to build experiments on their own has been limited in a variety of ways. The shipping of the first full release of the E-Prime system later this year will open up a new opportunity for addressing this problem. Because E-Prime promises to become the standard for building experiments in psychology, it is now possible to construct a Web-based resource that uses E-Prime as the delivery engine for a wide variety of instructional materials. This new system, funded by the National Science Foundation, is called STEP (System for the Teaching of Experimental Psychology). The goal of the STEP Project is to provide instructional materials that will facilitate the use of E-Prime in various learning contexts. We are now compiling a large set of classic experiments implemented in E-Prime and available over the Internet from http://step.psy.cmu.edu. The Web site also distributes instructional materials for building courses in experimental psychology based on E-Prime.

Awareness and working memory in strategy adaptivity.

To further the understanding of the mechanisms of strategy choice, in three experiments, we investigate the role of explicit awareness and working memory in strategy adaptivity. Experiment 1 provided correlational evidence that individual differences in strategy adaptivity to changing base rates are related to individual differences in awareness of those changes but appear not to be related to individual differences in working memory capacity. Experiment 2 replicated the role of awareness, and the results suggest that awareness at the time of the base-rate change, rather than afterwards, is related to increased strategy adaptivity. Experiment 3 measured working memory capacity using a different procedure and manipulated working memory load with a dual-task procedure; again, no apparent role of working memory capacity in strategy adaptivity was found. This juxtaposition of findings presents a challenge for existing models of strategy choice.

Another source of individual differences: strategy adaptivity to changing rates of success.

This article explores an alternative approach to the study of individual differences of cognitive function-- that people may have the same strategies but differential ability to adaptively select among them in response to success and failure feedback from the environment. Three studies involving the complex and dynamic Kanfer-Ackerman Air Traffic Control Task (P. L. Ackerman & R. Kanfer, 1994) demonstrate (a) that individuals do differ systematically along this strategy adaptivity dimension, (b) that those differences have important consequences for overall task performance, and (c) that the differences are primarily associated with reasoning ability and working-memory capacity.

Aortic aneurysm size and graft behavior after endovascular stent-grafting: clinical experiences and observations over 3 years.

PURPOSE: To assess the long-term safety and efficacy of aortic endografts in terms of clinical outcome, continuing aneurysm exclusion, and changes of aneurysm size and graft configuration. METHODS: Between August 1994 and July 1997, 190 patients (176 men; mean age 68.7 years, range 40-87) with aortic and aortoiliac aneurysms were treated with endovascular stent-grafts (Stentor, Vanguard, and EGS) in a tertiary care municipal hospital setting. Follow-up involved clinic visits every 3 to 6 months with contrast-enhanced computed tomography (CT), color duplex, and plain abdominal radiographs at regular intervals; angiography was used selectively. All data were collected prospectively and entered into a computerized database. RESULTS: Implantation was possible in 188 (98.9%) patients. Early conversion to open surgical repair was required in 14 (7.4%) patients. Primary endoleaks were detected in 32 (16.8%) patients. Perioperative mortality was 0.53% (1/190). During follow-up, 17 (8.9%) additional patients were converted to open repair over a mean 20.9 months. Thirty-seven secondary procedures to treat endoleaks and pelvic outflow occlusions were performed in 30 (15.8%) patients. Changes in stent configuration suggestive of endograft disintegration were observed in 31 (29.8%) of 104 abdominal radiographs. Intraluminal layering of thrombus was seen on contrast-enhanced CT images in 20 patients. A significant trend (chi(2)4 = 12.34, p < 0.025) toward aneurysm enlargement was seen in patients with persistent endoleaks at a mean 18-month follow-up. CONCLUSIONS: Although endoleaks after aortic stent-graft placement tend to cause ongoing aneurysm growth, we have also observed aneurysm shrinkage despite ongoing endoleak. The presence or absence of an endoleak in itself may be a poor predictor of successful stent-graft therapy. Lifelong surveillance is needed to assure successful aneurysm exclusion and stability or shrinkage of the aneurysm sac. Technical improvements in stent materials and design are necessary to guarantee long-term stability and safety of the device.

[Conventional aortic surgery after endovascular aortic reconstruction]. / Konventionelle Aortenchirurgie nach endovasculärer Aortenrekonstruktion.

INTRODUCTION: Endovascular therapy of aortic aneurysms is an attractive alternative to conventional aortic surgery. A number of patients, however, will fail endovascular therapy and require open surgical repair. METHODS: We report our experience with conversion to open aortic repair. Of 306 patients given endovascular therapy for an infrarenal aortic aneurysm, 30 (9.8%) required conversion to conventional repair. RESULTS: Thirteen patients (43.3%) suffered complications, 3 (10%) of which were fatal. Conversion to open aortic repair after endovascular therapy is technically more demanding than primary open repair, particularly because of clamp techniques and stent-extraction. CONCLUSIONS: Emergent conversion operations, especially when preceded by significant retroperitoneal bleeding from vascular tears due to endovascular manipulations are complicated by significant morbidity and mortality.

A mechanistic account of the mirror effect for word frequency: a computational model of remember-know judgments in a continuous recognition paradigm.

A theoretical account of the mirror effect for word frequency and of dissociations in the pattern of responding Remember vs. Know (R vs. K) for low- and high-frequency words was tested both empirically and computationally by comparing predicted with observed data theory in 3 experiments. The SAC (Source of Activation Confusion) theory of memory makes the novel prediction of more K responses for high- than for low-frequency words, for both old and new items. Two experiments used a continuous presentation and judgment paradigm that presented words up to 10 times. The computer simulation closely modeled the pattern of results, fitting new Know and Remember patterns of responding at each level of experimental presentation and for both levels of word frequency for each participant. Experiment 3 required list discrimination after each R response (Group 1) or after an R or K response (Group 2). List accuracy was better following R responses. All experiments were modeled using the same parameter values.

[Eversion endarterectomy--out?]. / Eversionsendarteriektomie--out?

Carotid eversion endarterectomy has become a well established alternative to conventional carotid endarterectomy. Similar perioperative morbidity and mortality results have been documented in several large clinical series. Our experience with carotid reconstructive surgery consists of 12,596 operations between 8/84 and 12/97, some 60% of which were performed using the eversion technique. Transient or permanent neurologic deficit was observed in 2.0%; 0.8% died after the procedure. Eversion endarterectomy should only be performed under suitable anatomic conditions. It is a challenging technique which requires advanced surgical skills and sound clinical judgement. The long-term rate of restenosis seems to be influenced favourably after eversion endarterectomy.

[Treatment of restenosis]. / Behandlung der Restenose.

Carotid restenosis after endarterectomy is observed in up to 24.1% of patients with long-term follow up. Indication for reintervention in asymptomatic patients however should be reserved for greater than 80% stenosis. Treatment options include repeat surgical reconstruction as well as intraoperative or percutaneous balloon angioplasty +/- stenting. We compared our past experience with 66 operative reconstructions in 64 patients with a recent series of 60 patients who underwent intraoperative balloon-dilatation and stenting. After conventional surgery 2 patients (3.1%) suffered a permanent neurological deficit, one patient developed a TIA (1.5%). After intraoperative dilation and stenting 8 patients (13.3%) suffered a stroke; 2 patients died after surgery (one stroke, one myocardial infarction) (mortality 3.3%). When compared to conventional operative repair intraoperative carotid balloon angioplasty and stenting of restenosis is complicated by a substantial increase in morbidity and mortality and cannot be recommended as routine therapy.

The importance of frameworks for directing empirical questions: reply to Goodie and Fantino (2000).

A. S. Goodie and E. Fantino (2000) make two main criticisms of the predictions of M. C. Lovett and C. D. Schunn's (1999) RCCL model. (RCCL is pronounced "ReCyCLe"; it stands for Represent the task, Construct a set of action strategies, Choose from among those strategies according to success rate, Learn new success rates.) In both cases, the authors believe the criticisms reflect a failure to appreciate the difference between broad frameworks and specific mathematical/computational models. In this article, the value of a broad framework, such as RCCL, in directing new empirical analyses and guiding theoretical development is shown. In particular, RCCL expands on existing work to reveal how variability and change in mental representations influence base-rate sensitivity. The authors also address several other issues raised by A. S. Goodie and E. Fantino (2000) and show that qualitative shifts in individuals' choice behavior are present in their original data--a key prediction of RCCL that does not appear in previous accounts.

[Imaging of aortic endoprostheses and their complications]. / Bildgebung von Aortenendoprothesen und deren Komplikationen.

PURPOSE: To determine the optimal postoperative imaging modality for the follow-up of patients with endoluminal aortic stent grafts. MATERIAL AND METHODS: From August 1994 to November 1997, 214 patients (194 male and 20 female) with abdominal and thoracic aortic aneurysms were treated with endovascular stent grafts. 137 patients (129 male, 8 female) with 89 tube grafts and 48 bifurcated grafts (45 EVT, 88 Stentor/Vanguard, 3 Chuter, 1 Talent) were evaluated with contrast-enhanced spiral-CT, duplex ultrasound, and DSA at a mean follow-up of 11.1 months. RESULTS: We found 12 persistent primary endoleaks (8.8%), 17 secondary endoleaks (12.4%), 8 limb occlusions (5.8%), 28 endoluminal thrombi lining the stent graft (20.4%), and 26 suture breakages of the stent frame (19%). In 9 patients (6.6%) the proximal end of the stent partially covered the renal arteries. In 3 patients (2.2%) a partial renal infarction was seen. Spiral-CT was able to demonstrate all the above changes except for 3 sidebranch endoleaks that were documented by duplex ultrasound only and 8 suture breaks seen on abdominal plain films only. The median aneurysm diameter decreased from 48 mm pre-operatively to 46 mm at 24 months post-operatively in patients with endoleaks and from 44 mm to 36 mm in patients without endoleak. For several patients the decreasing aneurysm diameter did not reliably correlate with complete exclusion of the aneurysm. CONCLUSION: For follow-up of endoluminal aortic stent grafts contrast-enhanced spiral-CT is superior to duplex ultrasound. DSA is necessary only for patients with complications requiring a secondary intervention.

Epidural versus general anesthesia: does anesthetic management influence early infrainguinal graft thrombosis?

A few contemporary reports have suggested that the use of epidural anesthesia may favorably influence early graft patency in patients undergoing infrainguinal revascularization. In order to test this hypothesis, we have retrospectively reviewed our experience with 303 primary femoropopliteal-tibial bypass procedures in 294 patients from January 1989 through June 1994. A total of 145 of these operations were done under epidural anesthesia (EA) and 158 under general anesthesia (GA); the demographic profiles for the patients in both of these groups were nearly identical. Thirteen patients (4.2%) died during the perioperative period (EA 3.4%, GA 5.0%; p = 0.48). Early graft thrombosis occurred in 35 patients (12%) during the same hospital admission (EA 14%, GA 9.4%; p = 0.28). There were no significant differences in the graft thrombosis rates for EA and GA with respect to surgical indications (claudication versus limb salvage), graft materials (vein versus synthetic), or the extent of revascularization (popliteal versus crural). Most graft failures appeared to be related to such conventional factors as disadvantaged outflow vessels and/or specific technical complications. Therefore, we conclude that the choice between EA and GA should continue to be made selectively on the basis of traditional anesthetic considerations.

Postoperative color flow duplex scanning in aortic endografting.

PURPOSE: To report the feasibility and sensitivity of duplex sonography compared to computed tomography (CT) for aortic endograft follow-up surveillance. METHODS: In a 26-month period, 113 aortic aneurysm patients received 79 tube and 34 bifurcated stent-grafts. Follow-up used contrast-enhanced CT scanning and duplex sonography with an intravenous ultrasound contrast agent (Levovist). RESULTS: Eleven patients (9.7%) were converted to open repair; 1 died from hemorrhagic shock secondary to retroperitoneal hematoma. The mean follow-up time was 7.2 months (range 1 to 24), during which 5 patients died of unrelated causes. Sixteen primary (within 30 days) and 5 secondary endoleaks were detected by duplex after tube graft implantation. Among 5 endoleaks due to retrograde side-branch perfusion, 3 were detected only with contrast-enhanced duplex scanning. Iliac artery occlusion was also documented using duplex; however, 2 stent fractures could not be seen with ultrasound. Ten primary endoleaks were detected in bifurcated stent-graft patients. One endoleak originating from the distal iliac limb anchoring site was missed by duplex owing to bowel gas. Graft limb thrombosis was clearly identified by lack of a flow signal on duplex. CONCLUSIONS: Duplex sonography could be a valuable, reliable, and economical surveillance tool for endovascular aortic reconstructions. The adjunctive use of an intravenous ultrasound contrast agent increased the sensitivity for detecting endoleak to a level comparable to contrast-enhanced CT scanning. However, stent fractures may not be seen on ultrasound, and bowel gas can interfere with obtaining an adequate image.

[Results and complications after endovascular reconstruction of aortic aneurysms]. / Ergebnisse und Komplikationen nach endovaskulärer Rekonstruktion von Aortenaneurysmen.

Between August 1994 and December 1996 137 patients (10 female and 127 male, mean age 66 yrs., range 27-85) with aortoiliac aneurysmal disease were treated with endovascular stent grafts. Pathology included 5 thoracic, 131 abdominal and 1 isolated iliac artery aneurysm. 88 straight tube grafts (75 Mintec, 12 EVT, 1 Chuter) and 43 bifurcated grafts (21 Mintec, 20 EVT, 2 Chuter) were implanted in the infrarenal aorta. 5 (Mintec) tube grafts were used for the thoracic aneurysms. One tapered tube graft was used to exclude the isolated iliac aneurysm. 11 patients (8%) required conversion to open surgical repair. This was due to defective devices in 5, device related occlusion of a renal artery in 2, aortic dissection in 1, occlusion of iliac outflow in 1, a large unmanageable proximal endoleak in 1 and a retroperitoneal bleeding resulting in hemorrhagic shock in 1 patient. There was one procedure related death for a mortality of 0.7%. Patients were followed every 3-6 months using CT with i.v. contrast and ultrasound duplex examinations with adjunctive usage of an intravenous ultrasound contrast agent (Levovist, Schering AG). Intraarterial DSA was used only when called for by thrombotic or stenotic complications. At a mean follow-up of 9.2 months (range 2-24 months) 16 (17%) primary and 8 (8.5%) secondary leaks (at the distal anchoring zone) were detected after implantation of tube grafts. 11 (25.6%) leaks were detected after implantation of bifurcated grafts. Iliac artery occlusion was observed in 2 patients after placement of a straight endograft, 6 times after reconstruction with a Mintec bifurcated device and 3 times after implantation of an EVT bifurcated endograft. Successful treatment of iliac artery occlusion without the need for subsequent amputation or major disability included extraanatomic bypass in 7 patients, PTA (3 patients) and implantation of wallstents (2 patients) or conservative management (1 patient).

Priming, analogy, and awareness in complex reasoning.

The mechanisms by which a concept used in solving one complex task can influence performance on another complex task were investigated. We tested the hypothesis that even when subjects do not spontaneously make an analogy between two domains, knowledge of one domain can still spontaneously influence reasoning about the other domain via the mechanism of priming. Four groups of subjects (two experimental and two control) were given a simulated biochemistry problem on Day 1 and a simulated molecular genetics problem on Day 2. For the two experimental groups, the solution to the biochemistry problem involved inhibition. For the two control groups, the solution did not involve inhibition. On Day 2, all subjects received the same version of the molecular genetics problem in which the solution involved the concept of inhibition. Subjects in the experimental conditions were more likely to attain the correct answer, to propose inhibition, and to propose inhibition early in the problem-solving session than were subjects in the control conditions. However, subjects in the experimental conditions made no reference to the biochemistry problem either in their verbal protocols or in a post-task questionnaire. The results are interpreted as demonstrating that an implicit process--priming--can make old knowledge available for current problem solving.

Small bowel necrosis associated with postoperative jejunal tube feeding.

BACKGROUND: Postoperative enteral nutrition using jejunal tube feeding is widely practiced and usually well tolerated. Functional intestinal complaints occur frequently but generally respond to alteration of the infusion rate or tube feeding formula. Occasionally, however, nonspecific signs of intestinal disturbance progress to a syndrome of abdominal distention, hypotension, and hypovolemic shock resulting in extensive small bowel necrosis. STUDY DESIGN: During a six-year period, four patients have been identified retrospectively who had this complication among 1,359 patients receiving jejunal tube feeding. Their clinical course was evaluated critically and compared with 11 cases described in the literature. RESULTS: Small bowel necrosis is a rare but highly morbid complication associated with postoperative jejunal tube feeding. Of 14 patients who had small bowel necrosis develop, 12 succumbed to this complication. The causative mechanism remains unclear, but is most likely the result of several factors. CONCLUSIONS: Tube feeding should be discontinued immediately and total parenteral nutrition should be considered in patients who have abdominal pain, abdominal distention, increased nasogastric drainage, and signs of intestinal ileus.